News:



  • March 28, 2024, 02:44:56 PM

Login with username, password and session length

Author Topic: REvolutions  (Read 33131 times)

Offline TDM

  • Trade Count: (0)
  • Captain
  • *****
  • Posts: 844
REvolutions
« on: September 15, 2017, 01:37:19 PM »
REvolutions
I am returning to my old project Revolutions
Initially I have designed this model to be possible either IC or Electric. I gave up the idea of going IC and now I go purely electric on this one.
Span 61in
Length 52.75
Height 7in
Weight goal sub 50oz
I am throwing all my knowledge in to this model. I am implementing the most advanced methods of modeling known to the modeling community, and as a fact is also most advanced to the manufacturing community too.  One goal is to have interchangeable parts coming out of the mold. The wings will be detachable plug in type. Also the horizontal stabilizer and the landing gear will be two piece plug in type.  Perhaps once all the molds are done the time from build start to first flight will be somewhere around 8 days (that is finished painted on the flight line). It can be faster but I would need another set of wing and horizontal molds but 8 days is alright with me.
Yes the model will be done with composite construction 100%. It will be made with carbon fiber foam core fiberglass throughout. There will be two types of composite construction being implemented in this one (hollow molding and compression molding). There will be No balsa in this build so if you want to see wood this is not the place. I will make special bell-cranks to adjust flaps bias. I might even go to logarithmic control but am not sure yet.
I designed this bird in CAD, right now I am cutting on my CNC machine from Aluminum billet one part at a time. After I cut them I will be the polishing of the molds in order to remove cutter marks and get a mirror finish. Once all are done I am going to treat the molds and after that I make parts.
Each goal you meet is a moment of happiness
Happiness is the harmony between what you think and what you do. Mahatma Gandhi

Offline TDM

  • Trade Count: (0)
  • Captain
  • *****
  • Posts: 844
Re: REvolutions
« Reply #1 on: September 15, 2017, 01:52:32 PM »
Some more pictures from CAD
Each goal you meet is a moment of happiness
Happiness is the harmony between what you think and what you do. Mahatma Gandhi

Offline Jeff Traxler

  • T-Bone
  • 2019 supporter
  • Trade Count: (0)
  • Captain
  • *
  • Posts: 645
Re: REvolutions
« Reply #2 on: September 16, 2017, 08:15:15 AM »
Looking forward to seeing more on this project.I am learning to make molds "old school" fiberglass lay up over plugs.Machining them from aluminum is very interesting indeed!! I love the composite stuff #^ #^
If you wanna sing the blues(Fly Stunt) you gotta pay your dues and "I know it don't come easy"

Offline TDM

  • Trade Count: (0)
  • Captain
  • *****
  • Posts: 844
Re: REvolutions
« Reply #3 on: September 16, 2017, 01:31:05 PM »
What is a PERKY  ??? ??? ???
Each goal you meet is a moment of happiness
Happiness is the harmony between what you think and what you do. Mahatma Gandhi

Offline TDM

  • Trade Count: (0)
  • Captain
  • *****
  • Posts: 844
Re: REvolutions
« Reply #4 on: September 16, 2017, 01:32:45 PM »
Looking forward to seeing more on this project.I am learning to make molds "old school" fiberglass lay up over plugs.Machining them from aluminum is very interesting indeed!! I love the composite stuff #^ #^

Yes they are good molds but never perfect. What part-parts are you trying to mold Jeff?

By the way gents I put some PICTURES in the FORUM GALLERY. They are under construction pictures. https://stunthanger.com/smf/index.php?action=gallery;cat=19
Each goal you meet is a moment of happiness
Happiness is the harmony between what you think and what you do. Mahatma Gandhi

Online John Rist

  • 24 supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 2944
Re: REvolutions
« Reply #5 on: September 17, 2017, 10:57:39 AM »
When finished do you plan to market a set of molded parts or perhaps a ARP  (P=paint)?
John Rist
AMA 56277

Offline TDM

  • Trade Count: (0)
  • Captain
  • *****
  • Posts: 844
Re: REvolutions
« Reply #6 on: September 18, 2017, 06:25:53 AM »
I have to check on the sales. Definitely i would want to recover the investment at a minimum.
Yes there may be an opportunity to get parts or whole model in our hands. You could just use some of the components too.
Each goal you meet is a moment of happiness
Happiness is the harmony between what you think and what you do. Mahatma Gandhi

Offline Darkstar1

  • Trade Count: (0)
  • Commander
  • ****
  • Posts: 324
Re: REvolutions
« Reply #7 on: September 18, 2017, 02:59:07 PM »
Will the motor be a front mount or rear (firewall mount) ?
Later,
Evolve or get left behind!

Offline TDM

  • Trade Count: (0)
  • Captain
  • *****
  • Posts: 844
Re: REvolutions
« Reply #8 on: September 19, 2017, 08:42:48 AM »
Will the motor be a front mount or rear (firewall mount) ?

The motor assembles from the front. Keep in mind that the nose comes off (Fuselage is 2 pieces)and there is easy access to the motor. The blue part is the machined insert. It will be turned on the lathe then milled to get the screw clearance holes and cooling slots etc.
Each goal you meet is a moment of happiness
Happiness is the harmony between what you think and what you do. Mahatma Gandhi

Offline TDM

  • Trade Count: (0)
  • Captain
  • *****
  • Posts: 844
Re: REvolutions
« Reply #9 on: September 26, 2017, 11:01:36 AM »
I looked in to Aluminium for making molds for fuselage and for the wing and prices and availability are through the roof.
Then I was looking for alternatives and what happened was that I stumbled on what is called "tooling boards"
Basically they are some kind of epoxy or urethane poured in to shapes and are relatively inexpensive. 2'x16'x60 275$ a piece plus ship. The bad part is that they do not sell this in small quantities so you are stuck with what you get but the good part is that it opened the door to make the mold in one shot rather than make several pieces that are assembled after molding. So now I have to reprogram all the fuselage and redo the CAD for the fuse and the wing. It is not a big deal but more of a nuisance and time lost. I wish I thought of it earlier. Now I am happy i had that problem because it made my life 300% easier.

Originally I wanted to make the flaps wing tip and wing separate and join the parts after the molding is done. Now I get the whole wing finished included the flaps with hinges attached out of the mold. Also I was going to mold the back side of the fuse the rudder fin vertical stab and turtle deck separate and join them after molding to create the rear side of the fuselage now i mold the whole piece in one shot and there will be no separate component joining to worry about.  #^ #^ #^ #^ #^ #^ #^

I plan to  S?P paint in the mold then lay the skins and vacuum bag the skins.  D>K After that I join the two mold halves  S?P. Next day after demolding presto finished part painted ready to be installed.  Maybe some gold leaf ink lines some clear to put the final touches but that should be about it.
Each goal you meet is a moment of happiness
Happiness is the harmony between what you think and what you do. Mahatma Gandhi

Offline Jeff Traxler

  • T-Bone
  • 2019 supporter
  • Trade Count: (0)
  • Captain
  • *
  • Posts: 645
Re: REvolutions
« Reply #10 on: September 27, 2017, 10:30:42 PM »
Traian,There is a place in Avon Ohio called Freeman Supply that has a similar product.Not sure how the prices are but they have it all the way up to 6 inches thick.Might look them up.Trax
If you wanna sing the blues(Fly Stunt) you gotta pay your dues and "I know it don't come easy"

Offline TDM

  • Trade Count: (0)
  • Captain
  • *****
  • Posts: 844
Re: REvolutions
« Reply #11 on: September 28, 2017, 10:02:59 AM »
Thanks Jeff
I saw Freeman and talked to their customer service.
I zeroed in on this product http://www.alro.com/divplastics/plasticsproduct_pp1052_hd.aspx. It is made by Axon and after talking to their support guise they said that it polishes very nicely. Some tooling boards require sealers (coat of epoxy sprayed or painted) to be able to impart a nice finish. PP-1052 does not need that at all. You can go from cut to sand and polish and you are done. What is even nicer is that it costs some 275$ per sheet plus ship which is nice vs 1000+ for aluminium.
Placing an order this week for this stuff.

If I am lucky and have an open machine I may make some as early chips next weekend.

One more thing about tooling board: If you make a mistake you can use a special matched filler glue patch the mistake, re cut the mold and you are good to go. Try to do that that in Aluminum. I might switch to this product from now on.
Each goal you meet is a moment of happiness
Happiness is the harmony between what you think and what you do. Mahatma Gandhi

Offline TDM

  • Trade Count: (0)
  • Captain
  • *****
  • Posts: 844
Re: REvolutions
« Reply #12 on: September 28, 2017, 10:57:40 AM »
Some more development.
I was working for a long time trying to think of a good take apart system and yesterday :! i came with the best idea i had to date  #^.
This is the inspiration: It comes from furniture cam locks. The practical idea is if i have removable nose i might as well use that to change batteries. I am planning to make some custom latches and put one on each side of the fuselage. If I want to remove the nose I use a flat driver half a turn then pull the nose off to change battery.

Initially i was afraid to have it come loose in flight but after that I came up with a simple solution and that is to add an O ring to the lock that will have several functions: first is an anti-slip so the lock does not come loose, second it stops the lock from falling out change position during handling of components transport etc, third it works as a bumper as you tighten the lock it squezes the oring. The pin can be sized to act a alignment pin on assembly to register the parts dead on in correct position.

Pin lock set should not be more than 5g. perhaps much lighter than that. If i make it out of aluminium it will be even lighter.
Each goal you meet is a moment of happiness
Happiness is the harmony between what you think and what you do. Mahatma Gandhi

Offline john e. holliday

  • 24 supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 22752
Re: REvolutions
« Reply #13 on: October 05, 2017, 06:53:20 PM »
I will be following this. D>K
John E. "DOC" Holliday
10421 West 56th Terrace
Shawnee, KANSAS  66203
AMA 23530  Have fun as I have and I am still breaking a record.

Offline TDM

  • Trade Count: (0)
  • Captain
  • *****
  • Posts: 844
Re: REvolutions
« Reply #14 on: October 06, 2017, 07:17:35 AM »
This is what I came up with so far.
The lock has 4 components plus an O-ring.
I made a model in CAD and analyzed the weight of the components. All 4 components add to about 3.05g in CAD and in reality they may be a tad lighter yet since the threads are not represented on two components and the cup gets 2 holes in it. So for sure it will be sub 3g per assembly. 7075 T6 will be the material used. The pin has a 1/8 diameter at the smallest point so i think it is strong enough even for the wing main attachment points. I will use this system through the whole model for removing all major components nose wings horizontal.
I am making some design decisions now. I can add a cap for battery access but I have decided to remove the nose for that. Half turn on each side with a driver and presto nose comes off. Change battery put nose back on half turn per side done battery is in. Since i plan to go with active timer i am gluing a plug to the nose that will connect disconnect as I remove the nose. The weakest point in the system is the threaded 8-32 screw. An aluminium 7075 screw sheer strength is 860lb, so with that in mind I think I am plenty safe here even with the weaker 7075 material.  There are two grades of 7075 one is 62000 PSI and the other 73000 PSI ratings. I calculated the strength for the weaker of the two.
At over 700 lb tensile strength conservative strength I am good with it. The real weak point is in the way the cup and the pin holder are being glued in the structure.
With that here are CAD pictures for the components. Thread are left out so use your imagination. On the lock you can see the space provided for the O-ring.
« Last Edit: February 20, 2018, 02:09:13 PM by Traian Dorin Morosanu »
Each goal you meet is a moment of happiness
Happiness is the harmony between what you think and what you do. Mahatma Gandhi

Offline Kim Doherty

  • Trade Count: (0)
  • Commander
  • ****
  • Posts: 154
Re: REvolutions
« Reply #15 on: October 06, 2017, 12:29:07 PM »
This is what I came up with so far.
The lock has 4 components plus an O-ring.
I made a model in CAD and analyzed the weight of the components. All 4 components add to about 3.05g in CAD and in reality they may be a tad lighter yet since the threads are not represented on two components and the cup gets 2 holes in it. So for sure it will be sub 3g per assembly. 7075 T6 will be the material used. The pin has a 1/8 diameter at the smallest point so i think it is strong enough even for the wing main attachment points. I will use this system through the whole model for removing all major components nose wings horizontal.
I am making some design decisions now. I can add a cap for battery access but I have decided to remove the nose for that. Half turn on each side with a driver and presto nose comes off. Change battery put nose back on half turn per side done battery is in. Since i plan to go with active timer i am gluing a plug to the nose that will connect disconnect as I remove the nose. The weakest point in the system is the threaded 8-32 screw. An aluminium 7075 screw sheer strength is 860lb, so with that in mind I think I am plenty safe here even with the weaker 7075 material.  There are two grades of 7075 one is 62000 PSI and the other 73000 PSI ratings. I calculated the strength for the weaker of the two.
At over 700 lb tensile strength conservative strength I am good with it. The real weak point is in the way the cup and the pin holder are being glued in the structure.
With that here are CAD pictures for the components. Thread are left out so use your imagination. On the lock you can see the space provided for the O-ring.

Traian,

Just some thoughts... $0.02 (CDN)

IMHO I would not exercise a structural take apart just to change the battery. Repeated use of such an over center cam type fastener will wear the cam and pin surface too fast. Once worn, there is no fix.  Use a hatch. Won't you have to have one regardless so you can access the other equipment. You said you will undo each side than take the nose off. Will you have two or four connectors? (two is not enough) How will you connect the battery if you are inserting it from the back? The front of the battery enclosure would seem to need to be closed in. Using very long wires is not weight friendly and it seems that you would need very long wires to be able to connect to. Then where will you put all that wire since it will have to go back inside the battery box?? Have you calculated where the CofG will be and what the fore/aft position of the battery will do to your desired CofG? Where will the battery actually sit? (vs the plane of the take apart face)  Gluing any plug permanently into the structure is not a good thing since all connectors wear. Once worn then what??

Not criticisms, just curious.

Kim.




Offline TDM

  • Trade Count: (0)
  • Captain
  • *****
  • Posts: 844
Re: REvolutions
« Reply #16 on: October 06, 2017, 03:05:31 PM »
Kim thanks and good points
First about the latch, both the pin and the lock are removable. If it gets loose it turn the pin in a little more. If is worn out I simply replace the two parts.
I have no solid data for battery position. Once the model is complete I will know exactly where the battery will go. Till then I have no idea. Also at that time I will figure out how I wil wire and layout the power related stuff.
Two pins can hold 1400lb why is that not enough?
Each goal you meet is a moment of happiness
Happiness is the harmony between what you think and what you do. Mahatma Gandhi

Offline TDM

  • Trade Count: (0)
  • Captain
  • *****
  • Posts: 844
Re: REvolutions
« Reply #17 on: October 17, 2017, 12:40:37 PM »
Kim you still did not answer my question.

I am pushing ahead on the take apart components.
According to the CAD models the 4 parts needed per assembly weigh in the 3g total weight. I played with the CNC and managed to make some prototypes to see how feasible this is. I am encouraged and think this is about as good as it gets for now.
« Last Edit: February 20, 2018, 02:09:35 PM by Traian Dorin Morosanu »
Each goal you meet is a moment of happiness
Happiness is the harmony between what you think and what you do. Mahatma Gandhi

Offline Kim Doherty

  • Trade Count: (0)
  • Commander
  • ****
  • Posts: 154
Re: REvolutions
« Reply #18 on: October 17, 2017, 02:59:41 PM »
Kim thanks and good points
First about the latch, both the pin and the lock are removable. If it gets loose it turn the pin in a little more. If is worn out I simply replace the two parts.
I have no solid data for battery position. Once the model is complete I will know exactly where the battery will go. Till then I have no idea. Also at that time I will figure out how I wil wire and layout the power related stuff.
Two pins can hold 1400lb why is that not enough?

Traian,

Sorry for the delay (oops!)

I have no problem with the pin and the way it is captured. As long as there is no possibility of vibration as the forces on the pieces are fairly large vs their size.

I would not want the fuselage sides/mating surfaces to carry any of the load. So three would be the minimum number of connectors.

But I will repeat the suggestion to NOT take the nose off each time you want to change the battery! Use a hatch.

As to the battery and the nose, I think you should take a similar fuselage and mount similar (the ones you will actually use would be preferable) components on it ( just with elastics and tape) to determine the approximate CofG. You would want it to balance slightly tail heavy with the battery in the rearmost position. This step will save you a lot of aggravation later on.

Looks cool!  (want a test pilot??  :)  )

Kim.

Offline TDM

  • Trade Count: (0)
  • Captain
  • *****
  • Posts: 844
Re: REvolutions
« Reply #19 on: October 18, 2017, 09:21:34 AM »
Traian,

Sorry for the delay (oops!)

I have no problem with the pin and the way it is captured. As long as there is no possibility of vibration as the forces on the pieces are fairly large vs their size.

I would not want the fuselage sides/mating surfaces to carry any of the load. So three would be the minimum number of connectors.

But I will repeat the suggestion to NOT take the nose off each time you want to change the battery! Use a hatch.

As to the battery and the nose, I think you should take a similar fuselage and mount similar (the ones you will actually use would be preferable) components on it ( just with elastics and tape) to determine the approximate CofG. You would want it to balance slightly tail heavy with the battery in the rearmost position. This step will save you a lot of aggravation later on.

Looks cool!  (want a test pilot??  :)  )

Kim.

I was worried about the parts coming loose too that is why i have added the Oring. It is similar to the same way a lock nuts work. The Oring will prevent it from coming loose.
As for the fuselage sides carrying the load the beauty of composite construction is that if you need extra strength you simply lay in a little extra material exactly where you need it. And since you have molds is easy to make a new part plane etc. and implement the new changes. For that it need to do some experimenting after i build the bird to see how it holds up to the normal use. There are 6 small pins (1/16 carbon) that align the fuselage sides in position to get a super nice parting line in addition to the 2 side latches and they are missing from the pictures.
The hatch will have to wait. I want to see how complicate is the nose removal in context and if i need a hatch it can be added. A hatch also means more complexity added to the whole thing and a weak spot extra parts and weight added to the model. Again I will have to build the first one to figure out what where will go regarding batteries ESC wiring electronics. The jury is still out on that one. 
Thanks for all advice.





Each goal you meet is a moment of happiness
Happiness is the harmony between what you think and what you do. Mahatma Gandhi

Offline Avaiojet

  • 22 supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 7468
  • Just here for the fun of it also.
Re: REvolutions
« Reply #20 on: October 18, 2017, 09:29:37 AM »
Traian,

I'm keeping an eye on this Thread with amazement.

Looks to me as though you're raising the bar quite a bit with this design.

I also have confidence, you do know what you are doing!

I'm learning stuff.

Charles
Trump Derangement Syndrome. TDS. 
Avaiojet Derangement Syndrome. ADS.
Amazing how ignorance can get in the way of the learning process.
If you're Trolled, you know you're doing something right.  Alpha Mike Foxtrot. "No one has ever made a difference by being like everyone else."  Marcus Cordeiro, The "Mark of Excellence," you will not be forgotten. "No amount of evidence will ever persuade an idiot."- Mark Twain. I look at the Forum as a place to contribute and make friends, some view it as a Realm where they could be King.   Proverb 11.9  "With his mouth the Godless destroys his neighbor..."  "Perhaps the greatest challenge in modeling is to build a competitive control line stunter that looks like a real airplane." David McCellan, 1980.

Offline TDM

  • Trade Count: (0)
  • Captain
  • *****
  • Posts: 844
Re: REvolutions
« Reply #21 on: October 20, 2017, 06:35:39 AM »
I made a test rig out of aluminium 6061. I assembled a latch and tested it using my fat ass body weight. One latch held to it just fine so at over 185lb of force. Moreover I threaded the latch pin in the 6061 aluminium. The real parts the latch will thread in 7075 which even in the lower strength rating is some over 40% stronger than the 6061 which means also those threads will be 40% stronger at minimum. So we can add another 40% to the 185lb to this test to come to the true strength of at least 250lb force for one assembly. In my book i call this overkill strength and I am happy with this result. 

The next target i want to work on is the bellcrank assembly. What i want to have in it is a NO TOOL necessary lead out wire connection to the bellcrank. The trick will be to make it light easy to use reliable. 

Charles yes I plan to push the existing envelope a little. And for all you who watch many thanks. I hope we can learn from each other and push this hobby forward. No one who did exactly like the one next to him has ever helped making any progress.

Traian
« Last Edit: October 20, 2017, 07:12:42 AM by Traian Dorin Morosanu »
Each goal you meet is a moment of happiness
Happiness is the harmony between what you think and what you do. Mahatma Gandhi

Offline john e. holliday

  • 24 supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 22752
Re: REvolutions
« Reply #22 on: October 23, 2017, 10:07:40 AM »
I am watching this as I like people who think out side of the box. H^^
John E. "DOC" Holliday
10421 West 56th Terrace
Shawnee, KANSAS  66203
AMA 23530  Have fun as I have and I am still breaking a record.

Offline TDM

  • Trade Count: (0)
  • Captain
  • *****
  • Posts: 844
Re: REvolutions
« Reply #23 on: October 31, 2017, 08:12:32 AM »
I have sample material coming in soon and I will start to make some chips on the CNC soon.
I figured out how to make the lead out removal on the bellcrank.
Each goal you meet is a moment of happiness
Happiness is the harmony between what you think and what you do. Mahatma Gandhi

Offline TDM

  • Trade Count: (0)
  • Captain
  • *****
  • Posts: 844
Re: REvolutions
« Reply #24 on: November 02, 2017, 07:51:43 AM »
I call this food for thought:
I have spent some time in the last 3 weeks crunching numbers in the thrust calculator and motor calculator, and I think I found something I call significant.  What is significant revolves about the idea that you can use higher pitch props running lower RPM that produce same thrust and Speed and this totally contrary the lower pitch high RPM currently employed by the CL community.
1: One blade prop is most efficient but since I do not want to go there I will use 2 blade props in the future. 
2: As the pitch increases many good thigs start to happen: the power requirements to drive that prop goes down, the rpm goes down, the lighter props come in place and become feasible, and off course the gyroscopic precession is cut nearly in half (by the way gyroscopic precession comes from the motor too mot only the prop), as the electric motors develop max torque at low RPM we run them toward their optimum sweet spot rather than stretching them out.
What is not so great is the fact that the current goes up with the lowering of RPM which creates more heat in the system and this brings me to the third point.
3: Bigger motors with low KV rating seep Amps. I was using a motor calculator for a 4250 motor 510KV running on 4S that spins the intended prop 13.25x7 6900rpm and the amps are in the low 20A range. This also addresses the low rpm current increase higher temperature.  Another thing a slightly oversize motor will do is to have plenty available power to quickly change rpm when commanded to do so.  Keep in mind a heavier motor doesn’t mean heavier system because whatever you add in the motor you take away from the battery. Consequently smaller batteries with lower cell count are also cheaper on the pocket too.
I feel I need to go back to this point I started with earlier and is about the lower pitch high RPM currently employed by the CL community. When the electric revolution started we took old models, threw in the electric motor and away we went. This was a great step forward towards reliable super consistent motor runs etc. The problem is the way we did it. We kept playing by IC rules instead of electric rules. We had roughly 36mm spacing in between the  IC motor mounts we went to the 35mm OD electric motors (the biggest we could fit in there), then since we had the props from the 40-60 piped motors or the ST60 we kept whatever was in the tool box and continued with it, that meant  we had to maintain the high rpm they demand and here we go we also needed the 5-6S systems to keep up with the demand from the prop to make possible our stunt flying.  The thig is even after that when we built new electric CL models we still kept the first tried systems without considering other alternatives.  It sure works but the question is whether or not is best it can be, my assessment is that we went the wrong direction here.
For REvolutionds I am starting at 13.25x7 (might have to up the pitch a little) and will go to a 4250 510KV motor running on 4S.   
Each goal you meet is a moment of happiness
Happiness is the harmony between what you think and what you do. Mahatma Gandhi

Online John Rist

  • 24 supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 2944
Re: REvolutions
« Reply #25 on: November 02, 2017, 12:05:06 PM »
I call this food for thought:
I have spent some time in the last 3 weeks crunching numbers in the thrust calculator and motor calculator, and I think I found something I call significant.  What is significant revolves about the idea that you can use higher pitch props running lower RPM that produce same thrust and Speed and this totally contrary the lower pitch high RPM currently employed by the CL community.
1: One blade prop is most efficient but since I do not want to go there I will use 2 blade props in the future. 
2: As the pitch increases many good thigs start to happen: the power requirements to drive that prop goes down, the rpm goes down, the lighter props come in place and become feasible, and off course the gyroscopic precession is cut nearly in half (by the way gyroscopic precession comes from the motor too mot only the prop), as the electric motors develop max torque at low RPM we run them toward their optimum sweet spot rather than stretching them out.
What is not so great is the fact that the current goes up with the lowering of RPM which creates more heat in the system and this brings me to the third point.
3: Bigger motors with low KV rating seep Amps. I was using a motor calculator for a 4250 motor 510KV running on 4S that spins the intended prop 13.25x7 6900rpm and the amps are in the low 20A range. This also addresses the low rpm current increase higher temperature.  Another thing a slightly oversize motor will do is to have plenty available power to quickly change rpm when commanded to do so.  Keep in mind a heavier motor doesn’t mean heavier system because whatever you add in the motor you take away from the battery. Consequently smaller batteries with lower cell count are also cheaper on the pocket too.
I feel I need to go back to this point I started with earlier and is about the lower pitch high RPM currently employed by the CL community. When the electric revolution started we took old models, threw in the electric motor and away we went. This was a great step forward towards reliable super consistent motor runs etc. The problem is the way we did it. We kept playing by IC rules instead of electric rules. We had roughly 36mm spacing in between the  IC motor mounts we went to the 35mm OD electric motors (the biggest we could fit in there), then since we had the props from the 40-60 piped motors or the ST60 we kept whatever was in the tool box and continued with it, that meant  we had to maintain the high rpm they demand and here we go we also needed the 5-6S systems to keep up with the demand from the prop to make possible our stunt flying.  The thig is even after that when we built new electric CL models we still kept the first tried systems without considering other alternatives.  It sure works but the question is whether or not is best it can be, my assessment is that we went the wrong direction here.
For REvolutionds I am starting at 13.25x7 (might have to up the pitch a little) and will go to a 4250 510KV motor running on 4S.   

This is the second time I have read something about low rpm high pitch prop setup.   The first problem it rpm governors.  The KR timer that I use won't go below 7500, well above the 6900 you propose.  Also the 4250 size motor you propose is huge.  So it begs the question:  what hardware, (motor, speed controller, timer, etc), are you looking at that fits your proposed setup?  ???
John Rist
AMA 56277

Offline Wolfgang Nieuwkamp

  • Trade Count: (0)
  • Commander
  • ****
  • Posts: 198
Re: REvolutions
« Reply #26 on: November 02, 2017, 12:15:02 PM »
Traian,
at low revs the motor torque will be higher than usual.
This implies that the C/G should be well above the exit point of the leadouts (with conventional props).

Offline Russell Bond

  • Bandolero
  • AMA Member
  • Trade Count: (0)
  • Captain
  • *
  • Posts: 450
Re: REvolutions
« Reply #27 on: November 02, 2017, 02:56:26 PM »
Not everyone runs low pitch props!

I'm using a wooden 13 x 7 three-blade on a 7.2 oz motor, 745 k/v at 7,700 rpm on a four cell battery.
Yes, less gyroscopic precession and the battery usage is the same as it was when I ran 6 pitch props at about 9,200 rpm.
This set-up was originated by Barry Robinson in the UK. He makes the props out of two bladed props.
It works great on my 72 oz model.
I think light models may not benefit as much as a heavy model with this set-up. (My theory)  ???
Bandolero

Offline Igor Burger

  • Trade Count: (0)
  • Admiral
  • ******
  • Posts: 2165
Re: REvolutions
« Reply #28 on: November 03, 2017, 03:53:44 AM »

2: As the pitch increases many good thigs start to happen: the power requirements to drive that prop goes down, the rpm goes down, the lighter props come in place and become feasible, and off course the gyroscopic precession is cut nearly in half (by the way gyroscopic precession comes from the motor too mot only the prop), as the electric motors develop max torque at low RPM we run them toward their optimum sweet spot rather than stretching them out.
What is not so great is the fact that the current goes up with the lowering of RPM which creates more heat in the system and this brings me to the third point.
3: Bigger motors with low KV rating seep Amps. I was using a motor calculator for a 4250 motor 510KV running on 4S that spins the intended prop 13.25x7 6900rpm and the amps are in the low 20A range. This also addresses the low rpm current increase higher temperature.  Another thing a slightly oversize motor will do is to have plenty available power to quickly change rpm when commanded to do so.  Keep in mind a heavier motor doesn’t mean heavier system because whatever you add in the motor you take away from the battery. Consequently smaller batteries with lower cell count are also cheaper on the pocket too.
   

Well we probably do something wrong if concept of 3 blade low pitch props developed and winning last decades is wrong. :-))

BTW do you have any math background to support that 2 blade high pitch prop has lower precession than high pitch 3 blade of the same power?



Offline Igor Burger

  • Trade Count: (0)
  • Admiral
  • ******
  • Posts: 2165
Re: REvolutions
« Reply #29 on: November 03, 2017, 04:03:54 AM »
Traian,
at low revs the motor torque will be higher than usual.
This implies that the C/G should be well above the exit point of the leadouts (with conventional props).

The torque is clear, the lower the RPM, the higher the torque at the same power, however you cannot balance the torque by CG position, it will make rolling as product of line pull changes (up wind, down wind, over head etc). It needs to be balanced by flaps and that is also not optimal, flight speed is stable, but also not 100% constant, so that shows the motor torque must be minimized = that is why we use high RPM setups. Current available outrunners are usually designed for RPM below 14000 rpm so current setups are designed for maximally 12000 RPM in boost - and that shows why we use 5" pitch props.

Offline TDM

  • Trade Count: (0)
  • Captain
  • *****
  • Posts: 844
Re: REvolutions
« Reply #30 on: November 03, 2017, 09:16:20 AM »
Thanks guys for the info. Just want to say that none of the power plant is set in stone for now. I will check with experimentation and see what will give good results. It might end up a Igor type setup or it might end up a Traian out of box setup. I can always change that it takes a few $$ a screwdriver and 4 screws.

Gyro precession will go down with two things in my common sense thinking. One is lighter components (anything turning) and rpm.
You drop rpm or rotating component weight you drop precession.

4250 is a big motor but only 30g heavier than what we use 175g to 205g. What I am thinking is to rob Peter to pay Paul here (when the motor is oversize it requires less current to do the job and batteries are getting smaller). Another thing happens is that transitions in rpm when commanded happen faster because it has more available power in reserve.

This is only theory at this moment that remains to be proven or disproved. I spent quite a few hours in the calculators looking to see the variation in power necessary to achieve a baseline thrust and speed. Long story short the first (theoretic) thing I found out is that the lower the number of propeller blades the lower the power was necessary to turn those props even though the diameter was going up to maintain thrust the same as in the baseline. The second (theoretic) thing I found out is that as the pitch goes up the power necessary to drive the prop goes down again since the rpm will go down (at same time as the pitch goes up also the diameter has to increase to maintain thrust at the new lower rpm). This all pushes against, and makes me question the current trend of low pitch high rpm everyone is copying what the person next to them are doing. I am willing to go the other way and try something new. The question is can we push the existing to the next level and start to use the electric power plants to the best they can deliver. We might already do that.
But there is only one way to check that out and that is experimenting and pushing the range till we push too far or we tried it all. If anyone has ventured in the high pitch low rpm setup please tell so I don't waste my time, else I will try it.

Igor I am not saying that whatever we do now is wrong. It sure works well and yes it won a world championship (congratulations to you Igor). Even though I think the person at the handle won it rather than the motor in the nose of the plane. I bet the result would be similar if you borrowed any model that showed up at the worlds. Igor you say something about torque and i am a learning kind of guy and I don't fully grasp the torque concept. Torque or moment of force is the force time the moment arm. In our case is the prop blade drag times the distance from center to the blade center of pressure (this is the torque we need to turn the prop blade). Prop blade is a wing in essence and the faster a wing flies the more drag it has to fight. If you have many wings (prop blades) so you have more drag sources and it sounds counter intuitive to up the Rpm and number of blades and expect the torque to go down. Maybe I understand this one wrong.


 
Each goal you meet is a moment of happiness
Happiness is the harmony between what you think and what you do. Mahatma Gandhi

Offline Igor Burger

  • Trade Count: (0)
  • Admiral
  • ******
  • Posts: 2165
Re: REvolutions
« Reply #31 on: November 03, 2017, 11:25:44 AM »
Well feeling is sometimes misleading, quick eyeballing tells me this:

12x5" prop of weight approximately 30g runs at 10 000 RPM

I will ignore units, because they does not matter as we are going to make ratio on the end and it is dimensionless number and converting will only make chaos.

Its moment of inertia is (1/12) x (12^2) x (30) = 360
and its precession is linear (with pitch speed) to angular momentum = moment of inertia * 10 000RPM = 360 * 10 000 = 3 600 000

We want prop with 2/3 of the original RPM (6666RPM) and 3/2 of pitch (7.5") compared to original prop
Such prop needs larger diameter to have the same power. (power is that wat make speed stability)
Since power goes with power of 4 to diameter, and we have 2/3 or original RPM we will need prop 3/2 larger - means diameter must be (3/2) ^ (1/4) = 1.11 - means the diameter must be 11% larger = 13.2" and its volume and thus weight going up with power of 3 is 1.11^3 * 30 = 41g
so now the same calculation for new prop:


moment of inertia is (1/12) x (13.2^2) x (41 ) = 595
and its precession is linear (with pitch speed) to angular momentum = moment of inertia * 6666 RPM = 3 966 270

so lowering rpm from 10 000 to 6666 will lead to precession which is  3 966 270 / 3 600 000 = 1.1 = 10% stronger.

Offline Wolfgang Nieuwkamp

  • Trade Count: (0)
  • Commander
  • ****
  • Posts: 198
Re: REvolutions
« Reply #32 on: November 03, 2017, 12:17:52 PM »
Could this be compensated by a Rabe Rudder with 10% more effect?

Offline TDM

  • Trade Count: (0)
  • Captain
  • *****
  • Posts: 844
Re: REvolutions
« Reply #33 on: November 03, 2017, 04:53:05 PM »
Possible to fix that with a Rabe ruder.

Igor I took a look at those numbers and you are right amusing that the bigger prop will weight more. However if I have a lighter prop or one that brakes even with the baseline prop i am in great shape then correct?
I know that your 3B prop is in the 16g range or somewhere about there. I also know that I can make my prop in the same range as yours is how do those calculations look then? I can get my 2B prop as heavy as your 3B easily.

So if i baseline your number with the original 30g

moment of inertia is (1/12) x (13.2^2) x (30 ) = 435.6
and its precession is linear (with pitch speed) to angular momentum = moment of inertia * 6666 RPM = 2 899 710
so lowering rpm from 10 000 to 6666 will lead to precession which is  290 3709 / 3 600 000 = .805 = 19.45% better with low rpm a 2B prop that breaks even in weight with your 3B prop.

That means the challenge is to produce the prop and I should be fine. And will definitely pocket the 20%. Does this sound right?

 
Each goal you meet is a moment of happiness
Happiness is the harmony between what you think and what you do. Mahatma Gandhi

Offline Igor Burger

  • Trade Count: (0)
  • Admiral
  • ******
  • Posts: 2165
Re: REvolutions
« Reply #34 on: November 04, 2017, 01:32:08 AM »
Igor I took a look at those numbers and you are right amusing that the bigger prop will weight more.

Yes larger prop heavier than smaller is my best bet  ;D

Offline TDM

  • Trade Count: (0)
  • Captain
  • *****
  • Posts: 844
Re: REvolutions
« Reply #35 on: November 05, 2017, 09:11:40 AM »
I received the tooling board sample and I want to say It looks very promising. So much so that  I may change the way I do hollow molding or anything that doesn’t require postcure from now on.
There are advantages and disadvantages going on here. Because it is softer than AL it is easier to finish that means easier to sand, with that I can afford a bigger step over and cut the machine time in half. The disadvantage is that postcure in the mold is harder as I don’t want to overheat the mold and also is harder to polish a softer material. Overall I don’t need postcure and I have to be a little more careful when sanding and polishing.
Each goal you meet is a moment of happiness
Happiness is the harmony between what you think and what you do. Mahatma Gandhi

Offline TDM

  • Trade Count: (0)
  • Captain
  • *****
  • Posts: 844
Re: REvolutions
« Reply #36 on: November 09, 2017, 08:27:16 AM »
I have received the sample material so I threw the material in the mill and started to make some chips. After about one hour of cutting here is the result.
I am happy with this material, it cuts nice it sands nice and now i need to find a good polish compound. Here you goo I call this eye candy  %^@. OK I need to stop druling.
The rest of the material comes in tomorrow or early next week.  #^ #^ #^
« Last Edit: February 20, 2018, 02:10:03 PM by Traian Dorin Morosanu »
Each goal you meet is a moment of happiness
Happiness is the harmony between what you think and what you do. Mahatma Gandhi

Offline Howard Rush

  • 22 supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 7805
Re: REvolutions
« Reply #37 on: November 09, 2017, 03:53:44 PM »
I got excited about this material until I realized that I don't have a mill, can't afford to get one, and wouldn't know how to operate one if I had one.  Nice mold, though.
The Jive Combat Team
Making combat and stunt great again

Offline TDM

  • Trade Count: (0)
  • Captain
  • *****
  • Posts: 844
Re: REvolutions
« Reply #38 on: November 10, 2017, 06:08:35 AM »
Howard
These type of projects are usually tackled by a team of people each one with a specialty. You have the aerodynamicist who created the overall design (shape), you have the engineer who puts the parts together and make them work, you have the draftsman who takes the engineers creation and creates the models, you have the machinist ho makes the molds and individual hardware reality, and finally you have a composite manufacturer who puts the final parts. 
Or you just have Traian who happens to have experience in all of the above.
That being said this is the current level of modeling in most disciplines that require absolute performance. You can’t find a speed model a glider or a high efficiency machine made out of balsa wood plywood and tissue paper. This is next generation modeling.  Some have already embraced this kind of modeling especially in the glider world some have elements of this in the control line world too.
At least I can stir your imagination and present the possibilities, the eternal WHAT IF.
I am quoting a quote I like very much “no one has ever made a difference by being like everyone else” and another one i like a lot "where there is a will there is a way".
Each goal you meet is a moment of happiness
Happiness is the harmony between what you think and what you do. Mahatma Gandhi

Offline Avaiojet

  • 22 supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 7468
  • Just here for the fun of it also.
Re: REvolutions
« Reply #39 on: November 10, 2017, 06:59:29 AM »
Traian,

Gotta give you credit for reinventing the wheel.

Outstanding!

Charles
Trump Derangement Syndrome. TDS. 
Avaiojet Derangement Syndrome. ADS.
Amazing how ignorance can get in the way of the learning process.
If you're Trolled, you know you're doing something right.  Alpha Mike Foxtrot. "No one has ever made a difference by being like everyone else."  Marcus Cordeiro, The "Mark of Excellence," you will not be forgotten. "No amount of evidence will ever persuade an idiot."- Mark Twain. I look at the Forum as a place to contribute and make friends, some view it as a Realm where they could be King.   Proverb 11.9  "With his mouth the Godless destroys his neighbor..."  "Perhaps the greatest challenge in modeling is to build a competitive control line stunter that looks like a real airplane." David McCellan, 1980.

Offline TDM

  • Trade Count: (0)
  • Captain
  • *****
  • Posts: 844
Re: REvolutions
« Reply #40 on: November 10, 2017, 01:29:02 PM »
Thanks for the encouragement.
Guess what the cat dragged in here. Two slabs of tooling board. I still work on cut strategy. The thing is that the machine doesn't have the travel to cover the whole part and because of that I have to work around the limitations.
Each goal you meet is a moment of happiness
Happiness is the harmony between what you think and what you do. Mahatma Gandhi

Offline TDM

  • Trade Count: (0)
  • Captain
  • *****
  • Posts: 844
Re: REvolutions
« Reply #41 on: November 20, 2017, 08:20:30 AM »
Depending on the part I will use 3 types of molding techniques.
Most parts (wing fuselage horizontal will be molded vacuum bag shells the I join them when i close the two halves of the mold. I might have some operations taking place after molding like cutting cooling pockets etc. The take apart hardware is installed during the close operation when I close the two halves.
The landing gear will employ two other techniques for molding. The struts will be done with compression molding and the wheel pants will be done with inflation bladder (overlap is necessary for the inflation bladder).

When you are done with the top and bottom you simply mix some splurge (Epoxy Cabosil Microbaloons combinations), and like you ice the cake, put this splurge on the edge, then you close the 2 halves of the mold. Those 2 halves have 2 alignment pins built in the mold so when you close them they will align within .001-.002in precision. There is no overlap here as all parts are finished bellow the parting line so you can close the mold without having the halves crashing in to each other.

A sandwich layout is preferred either glass balsa glass or glass foam glass will work well. Foam is better lighter but more expensive than balsa. If you go with balsa then 1/32 in the wings will be enough (add a couple of vertical walls inside) with 1/16 balsa in the fuselage will work too.
The beauty of composites is that if you are not happy with strength then you can make another wing panel or whatever part you want to in a couple of days. If you need extra strength in an area then add some material and strengthen that area. As long as you have the molds you can put anything in them and because it takes days to replace parts you can test anything. Carbon is not a requirement but if you put it on the outside surface then it will be a whole lot more durable just be careful to what you select because it will add weight fast.

What do you mean by "lay without a plug"?
Each goal you meet is a moment of happiness
Happiness is the harmony between what you think and what you do. Mahatma Gandhi

Offline TDM

  • Trade Count: (0)
  • Captain
  • *****
  • Posts: 844
Re: REvolutions
« Reply #42 on: November 20, 2017, 08:25:12 AM »
An update.
The CNC ATC is broken so until they fix the machine I am on stand by.  I was really hoping to cut these molds this week. If there was no bad luck i would not have any at all   >:( '' ~^
Each goal you meet is a moment of happiness
Happiness is the harmony between what you think and what you do. Mahatma Gandhi

Offline TDM

  • Trade Count: (0)
  • Captain
  • *****
  • Posts: 844
Re: REvolutions
« Reply #43 on: November 20, 2017, 11:41:02 AM »
Probably the heaviest way to do it and you hope the cloth conforms to the mold.

So you vacuum bag the top and bottom of the wing then trim down to the flange then glue the molds together and end up with a butt joint on the LE and TE.

Yes that way is heavy because you need to build up the thickness to get any kind of rigidity on the skin.

Almost:  Vacuum bag the top and bottom of the wing then glue the halves together and end up with a butt joint on the LE and TE.
Each goal you meet is a moment of happiness
Happiness is the harmony between what you think and what you do. Mahatma Gandhi

Offline TDM

  • Trade Count: (0)
  • Captain
  • *****
  • Posts: 844
Re: REvolutions
« Reply #44 on: November 21, 2017, 02:27:00 PM »
Today's work
Is a pain in the ass when the ATC is not working. Ideally you want to set the machine and go home. When you return next day the part is done.
Each goal you meet is a moment of happiness
Happiness is the harmony between what you think and what you do. Mahatma Gandhi

Offline jfv

  • 24 supporter
  • Trade Count: (0)
  • Captain
  • *
  • Posts: 633
Re: REvolutions
« Reply #45 on: November 21, 2017, 03:58:33 PM »
Very nice.  I'm very jealous.
Jim Vigani

Offline TDM

  • Trade Count: (0)
  • Captain
  • *****
  • Posts: 844
Re: REvolutions
« Reply #46 on: November 22, 2017, 05:51:43 PM »
The evil twin has arrived  VD~

The aluminium plates are used to hold the nose section and the back section together in perfect alignment so I can sand in assembly. That way when I assemble the nose section to the rear section the parting line will be perfect or so I am dreaming of.
Each goal you meet is a moment of happiness
Happiness is the harmony between what you think and what you do. Mahatma Gandhi

Offline Avaiojet

  • 22 supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 7468
  • Just here for the fun of it also.
Re: REvolutions
« Reply #47 on: November 22, 2017, 07:29:42 PM »
Traian,

Absolutely outstanding!  H^^

I've never seen this kind of workmanship in this Forum before?

There's also balloon bladders that are placed inside the mold and the material. When inflated they push the material against the mold. I believe some parts are made this way, wings for an example.

Or am I thinking of something else?

Great work!

Charles

Trump Derangement Syndrome. TDS. 
Avaiojet Derangement Syndrome. ADS.
Amazing how ignorance can get in the way of the learning process.
If you're Trolled, you know you're doing something right.  Alpha Mike Foxtrot. "No one has ever made a difference by being like everyone else."  Marcus Cordeiro, The "Mark of Excellence," you will not be forgotten. "No amount of evidence will ever persuade an idiot."- Mark Twain. I look at the Forum as a place to contribute and make friends, some view it as a Realm where they could be King.   Proverb 11.9  "With his mouth the Godless destroys his neighbor..."  "Perhaps the greatest challenge in modeling is to build a competitive control line stunter that looks like a real airplane." David McCellan, 1980.

Offline TDM

  • Trade Count: (0)
  • Captain
  • *****
  • Posts: 844
Re: REvolutions
« Reply #48 on: November 23, 2017, 06:37:53 AM »
Charles that is called “inflation bladder molding” it is good for parts that are fabric only like a only carbon fuselage (when you lay the material it stays on the mold walls without pulling off the mold) and for that you need a rigid mold because it has to take the pressure without distorting. I will use this technique in making the wheel pants for this bird. Ant that is the only place I will use this technique. And baloons are bad for bladders because the epoxy eats then they burst and make a mess. I had many of them burst and destroy hundreds of dollars 💵 worth of material.

Happy thanksgiving to everyone thanks for watching I hope we all learn something new and make better stuff all the time. Also thanks for all your impute and friendship.

Traian
Each goal you meet is a moment of happiness
Happiness is the harmony between what you think and what you do. Mahatma Gandhi

Offline TDM

  • Trade Count: (0)
  • Captain
  • *****
  • Posts: 844
Re: REvolutions
« Reply #49 on: November 28, 2017, 02:30:38 PM »
Since the machine is not behaving I am using the time polishing the fuselage molds. The part I do not like about this material is that is hard to see what is done or not done. As soon as it is wet (wet sanding) you do not see anything in there. You have to sand blind, and you have to dry it out and see the results from sanding.
But if that is the worst I am taking.
Each goal you meet is a moment of happiness
Happiness is the harmony between what you think and what you do. Mahatma Gandhi


Advertise Here
 


Advertise Here