OK, time to let everyone in on my motor mount.  The motor is front mounted and rear supported.  I made the mounts from 2024-T3 .063 aircraft grade aluminum.  The rear is supported by a flanged bearing that is press fit into the rear support.  Now these are the prototypes and I'll make another set that on the front mount the motor will sit down closer to the fuselage about 1/16 or so, do away with the cooling hole by the wires and raise the other cooling hole slightly to align with the one on the motor.  I'll also use some socket head bolts to hold the motor to the front mount.  I haven't checked how much drag the extra bearing puts on the system, but I will when I do the final assembly.  The mounts weigh just 8 grams and the motor is very rigid.  More so than just front mounting it.  Enjoy the pics.

That is a sweet mount!

And congratulations on being a GrandDad.

However it does sound like you are becoming a little wimpy---slowing down your building and all. TreeTown "legend" Jerry "Who" Meyer, when told by his daughter of her upcoming marriage,  told her "great, but I'll at the NATS!". 

Great stuff Crist.  The mounting idea is right on the money.  I really can't wait to see how this thing goes. 

By the way, I work in sheet a metal fabrication company and when you get a design you like, we have (2) lasers and (4) press brakes.  I think an electric mounting system for a profile would be a very marketable.  Your idea is right on.

We are desperately awaiting liftoff!! 

Take care!!   

Put me down for two - 1 with a 4mm ID bearing and one with a 5mm ID.  Invoice me through Paypal or send me a couple of prototypes to test.  TIA ---

Fantastic bit of design, Crist.  And congrats on the new family member -- we were just presented with our 8th grandson last week, to go along with our 3 grand-daughters - I haven't had him out to the field yet, but soon -- very soon.

Latest update.  The pushrod cover and scoop are on.  The final version of the motor mount has been fabricated and works very well.  I have to cover the elevators, and apply the "ink" lines on the flaps and elevators, hinge the elevators, then mount the motor and electronics.  Install the controls and do final set up.  Getting real close.

It prevents the spinner from "hanging" over the inboard side of the profile. 

Hi Crist:

Great job on the profile. It looks like a bunch of us had pretty much the same mounting idea concurently. I think the metal mount you came up with is ideal for the profile solution, but in a full-bodied ship a lighter version of this idea can be used. Dean Pappas and I came up with the mount that is in the attached photo; it is made entirely of plywood and we have been testing it in a mockup for several weeks. It is flawless and supports both ends of the motor.

We are all getting closer to optimizing this electric thing!

Later - Bob Hunt 

It's ready to go....almost!  I have finished it except I want to put on the lighter elevators.  They are 1/2 ounce lighter.  With the heavier elevators, as shown in the pics, it weighs 50 ounces almost exactly, 1418 grams.  That's with a 1 ounce of tip weight.  Right now it balances right at 25% and with the lighter elevators it will balance at 22% and weigh 49 1/2 ounces.  I want to start out with the forward CG then work back.  The specs are:
570 sq in
54 WS
27% tail volume
Scorpion SII-3020-890 front mounted and rear bearing supported
PolyNoOne 4S2P 3400mah battery
Castle Creations Phoenix 45A ESC
JMP-2 timer
Scorpion 2" spinner
Xoar 12 x 5 E Prop
Foam wing
All Monokote finish
Nelson Paints for touch up
4" bellcrank set forward of the CG
Ball link and carbon fiber pushrods
Set up for a Rabe Rudder or fixed "adjustable" rudder

Good luck with the plane!!! It really looks great. I'm looking forward to hearing how it flys!!! Maybe you will do better than me and not have to wait so long to get it flying. The NYC weather just wont cooperate. Next week I will be away so who knows when for me? Let us know how those batteries work out. I have been following the thread on RC Groups and they look promising.

I will Lee.  Maybe Saturday early.


I got them from RC Dude

http://www.rcdude.com/servlet/StoreFront

Well Saturday it flew!  The motor mounts worked very well.  My Eagle Tree FDR wouldn't download any data so I don't have any flight graphs to show.  When I got home I ended up reloading the software and it's working now.  So next time out I'll have some graphs.  Here are some numbers from what I could get from yesterday.  The battery mah was what the charger put back in.

Xoar prop 12 x 5
10600 rpm
5.4 laps
60 foot lines eye to eye
1942mah
The rpms are too high figuring that max we want to be about 75% (9600) of max rpms (12,800).  

Xoar Prop  12 x 6
9600 rpm
5.1+ laps
60 foot lines eye to eye
2521mah
2412mah
2388mah
2022mah

The 2022mah was the last flight of the day and I'm not sure why it was so low.  The wind was the calmest of all the flights too!  I'll do some more recording next time out.

Line tension was excellent with the 12 x 6 prop and very good with the 12 x 5 prop.  I didn't get the chance to try the APCE 12 x 6 prop up against the Xoar 12 x 6 but will next time out.  If the APCE 12 x 6 works well, then I'll try the reverse rotation version.

Spent most of my energies working on getting the airplane trimmed out and the way I want it to feel.  Looks like I have plenty of power and battery to spare.

We're on our way!

PS Dean,
Looks like your formula of 50 ounces X .7 = 35 / 14.8 volts = 2.4ah or 2400mah is right on the money.

Looks good in the air Crist. Also looks real close to the hangar, Floyd takes good pics. Wish I could have made it.

I also found some heavy duty "velcro" to hold down the ESC.  It is called 3M Dual Lock.  It's  low profile and the part number is SJ-4570.  I got a yard off of eBay.  I'll let everyone know how well it works out.  The engaged thichness is like a 1/10 of an inch!

<snip>
Search eBay for SJ-4570 Dual Lock and you'll find where I bought a yard for $8 shipped.

Well the Dual Lock worked very well in regards to not being so wobbly.  It worked quite well.  I'm still looking for something that has more grip to try my idea for a one handed disconnect.  Might just have to build a low profile "shelf" and zip tie it in place.

4-19-2009 Update:
I did build a shelf to mount the ESC.  It consists of a piece od 1/16 birch ply about 1 (h) x 1 1/2 (w) with 1/16 basswood on the backside with 3/16 gaps for the tie straps.  Touched it up with Nelson Paints and now the ESC is mounted firmly.  Do you think I should put a thin piece of foam between the ESC and shelf for some vibration dampening?

Even though I am away,I made it to a PC today and have to say congratulations on you successful first flights. How did those PolyNoOne batteries feel. I know you didn't log these flights.

Even though I am away,I made it to a PC today and have to say congratulations on you successful first flights. How did those PolyNoOne batteries feel. I know you didn't log these flights.

Barely warm at all.

Thanks William, Archie, and Dennis.

Alan,
Yeah, the new V2 could be the reason.  So far I like it.  Runs very smooth.

I designed the front mount to have the center of the shaft even with the outboard edge of the fuselage.  The aft mount is 1/16 "into" the fuselage thus giving me 2 degrees of right thrust.  Also the center of the rear bearing is 1/32 high giving me 1 degree of down thrust.  I mounted the front mount at an angle that was even with the front nose ring thus giving me the 1 degree down thrust.  Then I added the aft mount and it just barely touched the fuselage.  I lined up the mount for the required down thrust and tweaked the mounts for the right thrust and it tightened down just fine.  I ran the motor with no prop and monitored the current draw then I loosened the aft mount and saw no change in current draw.  Tightened the mount and the same thing.

Alan,
Yes, from PolyNoOne.  I did make a leadout adjustment but using another pack.  I have a total of just 2 cycles on each pack so far.  I'll keep my eye them to see if any of the batteries perfrom better than the others.  Wednesday evening is the next flying day.

OK guys, got out tonight and did some more prop testing.  The Eagle Tree performed well.  I tested 3 props dialed in to give me @5.2 sec laps.  I tested them flying about 70 seconds each time.  They were:
Xoar 12x6 428ma  @350W
APCE 12x6 377ma  @300W
RSM 12x5.5  419ma  @360W

Here is each graph:

Alan,
I'll need to do more testing.  The APCE 12x6 is definately has a higher "effective' pitch than 6 by evidence it runs at a lower rpm for the same 5.2 sec lap.  The RSM prop is very good!  I thought that it would get your attention!

I ordered a couple of 13 x 6 Xoar props to see how they will do.  I like the 9600 rpm because it is 75% of max rpm.  Pretty close to where we want to run our motors.... right?  I might end up trimming them down to get the total current draw to where I want it.  About 2600 to 2700mah.

Alan,
The 75% number came from a post a while ago I think from Dean explaining ECL systems.  He said, if I remember right, that he and Bob Hunt kept increasing the the motor rpm till about 75% showed to be the most efficient.  When I talk about 75%, I mean 75% of max rpm figuring the KV and battery voltage.  With a KV motor of 890 and a 4S battery voltage of 14.4 came out to 9612.  That's what I'm shooting for.  Then running the 9600 rpm I'll adjust the prop to bring up the total mah used to 2600-2700mah.

From what I have gathered from reading some other forums, when running at 75% rpm, the amp draw is really about 60% of the continuous amp rating.  The 3020-890 is rated at 45 amps continuous and at 75% rpm will be giving me about 28 amps.  These numbers all fall within where I want to run my setup.   

Alan,
Yeah, total system efficiency has a broad maximum.  I'm trying the lower pitch route first.  I know the prop says 6 pitch but the APC12x6 seems to be higher.  The reason I'm trying the lower pitches is seeing if that route does reduce wind up.  I know it does for nitro powered airplanes.  I'll use whatever prop/rpm that gives me the line tension I'm looking for and little or no wind up in the wind.  One thing for sure, there are certainly a lot of prop/rpm combos to try. 

Seeing I have a 3400mah battery, which seems to be plenty, I want to use all of the 80% rule-of-thumb capacity for the performance I need.  No sense leaving some performance on the table.  Tonight I'll be out along with Saturday morning doing some more testing and trimming.  Looks like a couple of good flying seesions are here.  I'll post some more graphs Saturday afternoon.

It'll take me a bit to figure out your graph.  Thanks for the post.

Here is today's graph.  I like the Xoar over the RSM prop.  My 13x6 Xoar props arrived in the mail after flying this morning.  I'll try them next time out.  Also I'm going to try an APC 13x4 repitched to 5 like I used last year but not cut down to 12 inches.  The total mah is 2267 and is pretty typical for this prop at 9600rpm.  Still plenty of power left to get to 2700mah!

Crist
GREAT work and thank you for reporting it all!

I think you might be on the wrong track for the EFFICIENCY theme tho.  It looks like you are trying to find the prop that uses the most energy (i.e. increasing battery usage to 2700 mah) to accomplish the task - that is to fly the Resolve-570 through a pattern.  Using MORE power to accomplish the same set of work is LESS efficient.  Of course the big question is "What prop FLIES the best?"

The approach of using larger diameter and lower RPM seems responable, however, according to generic "fan laws":

* Power required increases as the 3rd power of RPM - however
* Power required increases as the 5th power of DIAMETER

That suggests that increasing the diameter is the wrong way to go to increase efficiency unless there is a very large reduction in RPM to offset it.

The "Swinger" you saw me fly at FCM last year used around 1800-1850 mah per flight: 560 sq in, 50 oz, 61' lines, 5.1 lap times using a 10x5 APC-E.  In short the Swinger physical dimensions are in the same ballpark as the Resolve-570, but seemed to use less power.

All of this: a long and windy way of asking that you also try a SMALLER prop, like the 11x5.5 APC-E, probably at around 9500 RPM to achieve your goal.  THen try a 10x5 (if you have enough kV) just to finish "mapping" the power optins like Alan's chart.


I test flew the Swinger with a 3000mah battery.  When it was obvious that this was more battery than needed I switched to a 2500 for a roughly 2 oz weight save.  Next time out I want to try the 2350's, then see if I am brave enough to go to 2100's - but that will be cutting it a bit fine.


Another way to use more battery: go to longer lines and a little more RPM to maintain lap times....

Maybe we should make a poll to see what prop we want Crist to test!

Right now the APC 12-6 seems to win the most economical for level flight (based on Crist's first flights). I'm guessing that is partly due to the thinness of the APC vs the other two 12" diameter props. Not sure how an APC 11-5.5 would compare, once dialed in to the lap speed.

It is a PITA to adjust the rpm to get the right lap speed, at least a few flights. I just bought one of Will Hubin's new timers, and it looks like the way to set a a series of 2 minute flights for dialing in a run (with ESC in normal governor mode).

One argument for diameter is how it performs for climbing and braking--I think you win there with bigger diameter. Not sure when the P-factor starts to make life miserable for you though--does the pusher help there??. I know for my Nobler that I am at the diameter limit (12") wrt prop clearance, unless I go to 4" wheels!

OK guys here's the deal.  If you had, lets say, a Scorpion 3020-890 890Kv motor and, lets says, a 4S 3400mah battery, and you were going to put it in, lets say, a 50 ounce stunter on, lets say, 60 foot lines eye to eye and want lap times of, lets say, 5.2-5.4 seconds.  What kind of a set up would you use and why?