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Electric Stunt => Gettin all AMP'ed up! => Topic started by: Douglas Ames on July 31, 2011, 12:12:27 AM
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Anyone have experience with OS new line of electric motors?
I like the marketing relevant to glow sizes for us electron challenged types, however they're still publishing the 30 yr old disparity between a 4 stroke and 2 stroke. I also like the built-in cooling fan and best of all- a real threaded prop shaft!, not some adapter with set screws. They look excellent, OS quality.
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The motor looks like it comes with the "clamp type" adapter as per photo.
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Guys,
I just bought one on Friday the OS 3825-750 and hope to get it on the test stand this week. I want to put it in my profile ship to replace an AXI 2826-10. I expect the OS to have a little quicker response out of the corners and allow me to slow the ship down. Right now I fly a 5.25 lap on 64' lines and would like to get to a 5.35. Recently I trying the BH/PW forward CG moving it from 23% MAC to 15% and it worked very well, flattened the bottoms and punched through the wind. The OS is about 1/8" larger diameter than the AXI and should have a little more torque to spin up as the load is applied. I tried slowing the AXI setup to the lower lap time (depitched the 12x6 APCE P) but it is a little soft up top in the wind. Will let you know how this works out.
Best, DennisT
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They look to be HV motors (40 size = 6S cells). Also they look to be rear mount only? ::)
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The motor looks like it comes with the "clamp type" adapter as per photo.
PFFffffffffsssssss-phut... The sound of my enthusiasm deflating.
I've watched one of our Tulsa Gluedobbers lose a prop hub, not a pretty sight. I still want to try electric though.
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whats the issue withe clamp collets? I ahve been using them for the last 2 years with no issues
the RC guys have been using them forever - with not many issues.
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There's nothing wrong with them, they work great.... ;D
However, I don't like the idea of the ones that have grub screws on the side to hold them tight, I'd be worried it may put the prop shaft very slightly out of center...........never used one though........
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I just checked mine and it is the normal "collet clamp" type that we use on every other motor, no set screws. If someone had one come off they just didn't tighten it, this can be a problem with wood props as the hub crushes a little and needs to be snugged every now and then.
Best, DennisT
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Where are they coming from and can I get one now?
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DS1,
I got mine from my local hobby shop, just was doing a little impulse shopping and saw it bought it. I assume they are getting them from Great Planes were they get their other OS stuff from. Tower may have them but its not on the web site yet, call them.
Best, DennisT
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You won't be able to pull off a prop with a clamp collett. Have used them on E-Flight 10,15, and 25.
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Dennis,
Is it rear mount only?
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We ran one at the club meeting on July 23rd and it's a rear mount only...
here is a source from Florida
http://www.gravesrc.com/SearchResults.asp?Search=os+brushless
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Just ordered a motor. At least they had them in stock. Tower has been delaying them for two months now.
Thanks.
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Graves RC had two in stock the first one went to a CL person in the Denver area, now the second one is gone. Kinda neat that the RC guys didn't get the first ones shipped out.
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What's the beef with the rear mount? Are they not holding up to the high G pitch changes of C/L? Aren't there aftermarket clamshell mounts that would fit? ...or make your own cradle/ brace with ply.
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Doug,
In the past the idea of the front mount was to distribute the turning forces on the bearings between the prop on one side of the mount and the motor on the other. If you want to have just the single mount the front mount would distribute the load on the bearing/shaft a little more evenly.
The other option is the way is with and external stabilizing bearing. Bob H started adding a rear external bearing (with the front mount motor) to stabilize the motor and spread the force even better, several others have tried this and it seems to work well and also keeps the prop/motor pointing straight ahead during maneuvers.
Recently, I saw a photo of an installation with the motor rear mounted that had the shaft passing though an external front bearing, this should do the same thing that was done with the front mount. I know some have used the rear mount with no problems I think its just a matter of personal preference.
Best, DennisT
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Just back from the flying field with the new OS. It seems to be a good motor. The rear mount bracket was changed to fit the model. The bolt pattern is the same as the Hacker & Arrowind. Actually I was a straight swap I already had a mount bracket lying around. Another plus is the collet is metal not aluminum so U can take a 10mm wrench and tighten up the prop. Was also able to put on a spinner directly to the shaft using Tru Turns existing hardware. A metric screw fits the inner shaft. I finally was able to use it with the Ice 50 lite at set RPM with the APC 13 x 4.5 prop the thin one. At 9400 RPM I get a 5.5 lap and when the wind came up It held it's own. But theres just one negative the mounted fan up front is really just a bunch of small holes. I serves its purpose but up close it is a bit loud. Now after I got back from the field guess what, Tower finally has them in stock and I should have one here in Monday mornings mail. So now I have a couple of back up motors for my Plettys.
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Tower has them in stock now, at least in limited quantities. I ordered the 30-size on Friday and it has already shipped. 750 KV rating, probably a good equivalent for the AXi 2826-12.
If these are typical OS quality you may come to regard the Plettys as your "backup" motors!
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Just back from the flying field with the new OS. It seems to be a good motor. The rear mount bracket was changed to fit the model. The bolt pattern is the same as the Hacker & Arrowind. Actually I was a straight swap I already had a mount bracket lying around. Another plus is the collet is metal not aluminum so U can take a 10mm wrench and tighten up the prop. Was also able to put on a spinner directly to the shaft using Tru Turns existing hardware. A metric screw fits the inner shaft. I finally was able to use it with the Ice 50 lite at set RPM with the APC 13 x 4.5 prop the thin one. At 9400 RPM I get a 5.5 lap and when the wind came up It held it's own. But theres just one negative the mounted fan up front is really just a bunch of small holes. I serves its purpose but up close it is a bit loud. Now after I got back from the field guess what, Tower finally has them in stock and I should have one here in Monday mornings mail. So now I have a couple of back up motors for my Plettys.
Sounds good! I'm partial to OS engines as you can guess.
Noise wouldn't be an issue, as long as the fan worked.
Some matching vents in your cowl would be in order.
"Plettys" = ??
Is KV the standard rating for model motors now? 746KV = 1 HP, correct?
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I can get used to the noise. The fan does work well, The OS Is close to a Pletty 20-16 which has 720 kv and 10 poles.
The OS has 14 poles. The vents in the cowl are just fine I just need to find a suitable replacement for the Eratix cowl
E Flite hasn't had any available for the past three months now. So I e-mailed their tech support about some suitable replacements.
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Received my 3825-750 today. It is beautifully made, and all accessory items are too. The collet that tightens on the 5mm shaft appears to be steel, as noted above. If the bolt pattern is the same I may swap it for the AXi in my Legacy to test it on 5S batteries. I was a little disappointed to see it is made in China rather than Japan but guess I shouldn't be surprised.
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... Is KV the standard rating for model motors now? 746KV = 1 HP, correct?
Hi Douglas,
No, the Kv (actually Capital K - subscript v) is the motor RPM constant, usually stated in RPM per Volt.
Of course, the fact that 746 Watts is very close to 1 horsepower helped to add confusion.
Regards,
Dean P.
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Does the OS motor have the 3rd bearing to support the "can" the same as the Orbit has?
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Hi All, The OS motor looks good so far, and thanks to all that have reported on it. The concern that I have about the centrifugal type fan up front is how to cool the motor. I have tested the MVVS 6,5/910 motors for a few years already and they are beautifully made with top class bearings. The fan is the same system, and the motor was difficult to cool when used with the fan in front. The shaft extends on both sides, and when I used the motor with the wires and mount up front (fan at the rear) then it runs much cooler.
Looking at the system, the air is pulled through the casing from the rear, or wire side of the motor. This air then needs to get out somewhere so the nose construction is quite important for this setup. If hot air is been extracted by the fan and it flows back to the rear, then it sounds to me like a recipe for disaster. E-Max has now produced a new range called "Grand Turbo" or GT series and they look the same. I'm busy tested the .40 size version now in and old Nobler to see how the cooling works.
It will be interesting to see how the OS tests work out. Thanks.
Keith R
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Keith,
Have you tried to change the shaft position to make it a front mount?
Best, DennisT
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So, Does the on board cooling fan work for us or against us if using a pusher prop. Or does it not matter?
TTFN
John.
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So, Does the on board cooling fan work for us or against us if using a pusher prop. Or does it not matter?
TTFN
John.
Good question!!!
Dean
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I think it doesn't matter since the holes are straight so I believe it should work either way.
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Keith,
Have you tried to change the shaft position to make it a front mount?
Best, DennisT
Hi Dennis, Yes that's what I meant about mounting the motor the other way around with the fan at the back. It ran a lot cooler. As you can see from the photo of the MVVS motor, the shaft extends on both sides so it's easy to use it either way. It just makes more sense from an airflow point of view to run it with air coming through the front and exiting through the fan at the rear.
As Darrel mentions, the fan blades are straight as per any centrifugal fan, so it does not matter which way the motor spins. I use mine right now with the APC 12 x 6 pusher prop. It's a good motor, and the price is about the same as the AXI of similar size. The only problem is that the windings are a little high in resistance to make it a great stunt motor, but it still works rather well. It will work better at a higher rpm than I use with the 12 x 6, so I'm going to get some of the new 13 x 5,5 props from Dennis Adamisin.
Keith R
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Hi Dennis, Yes that's what I meant about mounting the motor the other way around with the fan at the back. It ran a lot cooler. As you can see from the photo of the MVVS motor, the shaft extends on both sides so it's easy to use it either way. It just makes more sense from an airflow point of view to run it with air coming through the front and exiting through the fan at the rear.
As Darrel mentions, the fan blades are straight as per any centrifugal fan, so it does not matter which way the motor spins. I use mine right now with the APC 12 x 6 pusher prop. It's a good motor, and the price is about the same as the AXI of similar size. The only problem is that the windings are a little high in resistance to make it a great stunt motor, but it still works rather well. It will work better at a higher rpm than I use with the 12 x 6, so I'm going to get some of the new 13 x 5,5 props from Dennis Adamisin.
Keith R
So does that mean you can't lower the RPM as much as one with a lower res. windings? Will it draw more amps/ run hotter?
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The higher winding resistance wastes power in the form of heat (current squared x resistance). A good stunt motor will have a lower resistance and strong magnets for more torque, so the governor system can work better. As I said it's a good motor anyway, it's just not maximized for our needs. Everything else about the motor is top class. I've been flying mine now for for more than two years, and it is still performing well.
Keith R
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internal resistance is very close in relation with magnet strength ... stronger magnets in the same frame means lower resistance (if the Kv is the same)
but efficient motor needs proper balance between internal resistence and no load current, or better written, the iron loses and copper loses must be aproximately equivalent, and while we use our motor at relatively high rpm, we typically get good results on motor wit rather lower no load current then internal resistance (AXI, MVVS) compared to low Ri motors with higher Io (MEGA, MPJ) ... while indoor models benefit on low Ri motors, because they run on low rpm ~4000 with large prop
regarding torque ... torque is function of motors Kv and current in winding, so does not matter if magnets are strong or not, if the Kv and current is the same, the torque is also the same (aproximately), the difference is in internal resistance as I wrote which is smaller, and in the no load current, which is higher, so we cannot benefit from stronger magnets, if such motor runs at disballanced configuratin in high RPM, it is just not automatical that stronger magnets give better result
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Thanks Igor,
You explained the torque story well..... as always. What do you think about my question on airflow through the motor with the configuration like the OS, or MVVS when you run it with the fan in front?
Keith R
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Thanks ..
regarding the orientation, I do not know exactly, Logic says that it will be dood to have the flow the same direction and not mix hot and cold air, but I have seen studies for pressure gradients on fuselage at spinner, and it shows that there is underpressure at back plate of the spinner, so it can make the flow reverse ... howevere it was fuselage of aerodynamically clean glider, I woud say and your measurements shows it that if we have so large openings for cool air, it will be better to have fan on back side, but I had model with both configurations with AXI motor without fan and I did not measure clear difference, but it was on two different models, in different conditions etc ... so for me - hard to say :-))
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Here is what I mean ... if the fuselage is like that airfoil on the first picture, then you can see the presuure at end of the spinner is low, if you fill fuselage by fresh air in front of the nose, then the air will run OUT of the spinner, and in that case it is logical to have the fan on that place ... but if the fan is deeper in the fuselage because of longer shaft, it could be better to have it on the back side ... optimal will be to bring fresh air directly to back side of the motor, fan on front of it and exhaust at spinner (the rest of the fuselage sealed) ... or for example inlet on left side of the fuselage, where is higher pressure and outlet (beside of the spinner) on right side at the fan, close the spinner
it also shows, that those spinners with vent in front, needs really large hole and sealed back side if it should work well
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Thanks again Igor, so what you're saying is that a motor like the OS could be mounted with the prop on the fan side and it could work under the right conditions. Airflow is not always easy to figure through our models, so it will be interesting to hear more reports from the guys using the OS motors. I'll do some more testing myself and then start a new thread on this later.
To Douglas who started this thread.......sorry for getting a little off the subject. I'm sure that OS quality will make sure that their electric motors are very good. Time will tell if they will work well for stunt. Don't let the apparent complications put you off having a go at e-stunt though. Just try it anyway, but beware, you WILL get hooked! If you enjoy flying well and getting a decent motor run on each flight, the electric power is totally unbeatable. If you just enjoy the sound, smell and goo of a wet setup, then stick with Stinky Power!
Keith R
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Perhaps standoffs can be used by those of us , like myself, who already have front mounted motors and desire more cooling. Four standoffs would mount to the rear x-mount.
If large, torquey gassers can utilize standoffs, I'm sure small electric motors can, too. However, I'm not sure it would be worth all the work since there are a number of very fine motors that can either be front or rear mounted and standoffs will add weight.
Think I just talked myself out of it (lol) !
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Guys,
I received an email back from the OS tech support about changing to a front mount system with these motors, short answer is - NO. The shaft is machined with flat spots for the rear coller and he indicated that you can't just slide the shaft through. I did remove the coller on mine and ya there are two flats machined in (I didn't remove the fan to check there). Good design but back if you want to run the front mount. I think with the fan in front pulling air from the back it will be difficult to keep clean cool air flowing through the motor without a lot of trouble.
Best, DennisT
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Hi Gang,
One of the first of my E-Stunt pencil doodles made during boring business meetings was of a scheme to take air from a chin scoop, turn it upward into the back part of a sealed motor compartment, take the airflow forward through the motor, and then exit from fake turboprop exhausts which would be placed immediately behind the spinner. With a front mounted centrifugal fan, this scheme would be a natural ... and the chin scoop could be moved aft for better appearance!
The fake turbo exhausts could even be replaced with pylon-racer styled cheek cowls with no entry in the front, only an exit out the back. These would pull air out of the front of the motor bay.
Now I know what I am doing with that Werwage Vulcan I was planning on!
Dean P.
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Hi Dean,
That sounds like a good plan! Just looking at Jose's Shark conversion, I see that his Plettie is also mounted this way. Maybe the Shark as enough space around the nose for this to work? It also comes down to the way we try to run our motors I suppose. If they are not working too hard in the first place then this is not really a big issue.
Keith R