Official FMS 1500mm P-47D Razorback Thread

[OV10]

Yes, the 460kv stock motor should be fine 4S and that prop. It will be a bit slow, but vertical should be impressive. Ecalc is showing 78A at full throttle :).

I wouldn't bet on it.....the stock motor rating is 70A

[F106DeltaDart]

My bad. I messed up inputting the data. I put 6 in the # of blades box and 4 in for the pitch :p. With the corrected input, I'm getting a max current draw of about 50A, so it should be well spec.

[OV10]

Other option is this motor: https://hobbyking.com/en_us/turnigy-...ner-motor.html, size and KV both look spot on for 6S. Might be a nice option if it still needs a bit more punch than the stock motor or the 580kv.

I saw that earlier and thus the reason for saying no HK options because this one is only rated @ 53A

[TiredIronGRB]

My bad. I messed up inputting the data. I put 6 in the # of blades box and 4 in for the pitch :p. With the corrected input, I'm getting a max current draw of about 50A, so it should be well spec.

What about the 580KV?

[F106DeltaDart]

What about the 580KV?

About 79A from ecalc, which matches what I have measured on the Bearcat. I believe it registered at about 75A on my wattmeter at full.

[F106DeltaDart]

I saw that earlier and thus the reason for saying no HK options because this one is only rated @ 53A

True, but I've pushed those ratings before (especially which the SK3 motors) and never had too much of an issue. There is generally a pretty good factor of safety built in to most of these motors in terms of their manufacturers rating. On top of that, multiblade props unload significantly in flight, and current only gets exponential at the upper limit of the throttle. If you are planning on flying scale with a few vertical climbs and one or two high speed passes, its fine. But, if you were to fly full throttle the whole time, then I'd be more concerned with the ratings. Its always a bit of risk to push the equipment, but it is nice to have the extra power there for large diameter loops, or to pull the plane out of trouble.

[OV10]

My bad. I messed up inputting the data. I put 6 in the # of blades box and 4 in for the pitch :p. With the corrected input, I'm getting a max current draw of about 50A, so it should be well spec.

In this case the stock 460kV run on 4S looks like a winner.
This 16" prop on the HSD skyraider with the stock 5060-300kV was turning 6660rpm
This 16" prop on the stock Razor with 4S is 6808rpm.
I know that the Skyraider clipped along so I don't think this set up will be a dog.
OK TI......stock motor and ESC but 4S power with the 16" prop and tell us your finding........OHHHH YEAH !!!!!!

[F106DeltaDart]

Awesome! Its also showing 80A with the 17x10 1700mm P-47 prop.. Hmm, I think I will try it on the stock setup on 4S with an ESC swap. This is looking a lot easier (and cheaper) than I thought it would be.

[Aros]

Admittedly I am no electrical student but going from a 6S to 4S setup, there's going to be some serious power loss, no?

[TiredIronGRB]

OK TI......stock motor and ESC but 4S power with the 16" prop and tell us your finding........OHHHH YEAH !!!!!!

On stock motor, ESC with 4S power and the 16" prop it pulls a max of 60A and 840W.

[F106DeltaDart]

This morning, while waiting for my P-47, I decided to do a side by side comparison of all of the options.

Important Note: These are NOT by any means exact numbers. They will give you an idea of how the power systems will perform relative to each other. Pitch speed is always off for multiblades in ecalc, I have the 580kv setup on my Bearcat and it is significantly faster than 39 mph at full throttle, so do NOT see this as entirely representative at the top speed. These are all estimated at static conditions at full throttle. Also, numbers supplied by the manufacturers aren't always accurate to KV or prop Pitch. This makes a BIG difference in the calculations, so beware if things don't quite match up.


Stock System

460kv Motor (estimated by using a 5045 450kv motor in ecalc, the FMS 460kv was not in the database yet), 14x8 4 blade and 6S:

77A
1709 Watts
62 mph pitch speed

(1) Stock System on 4S with 16x8 Skyraider Prop

60A
888 Watts
43 mph pitch speed


(2) Stock System on 6S with 16x8 Skyraider Prop

111A
2464 Watts
57 mph pitch speed

(3) FMS 4250 580kv with Skyraider Prop on 4S
93A
1376 Watts
49 mph Pitch Speed

(4) Stock System with 17x10 1700mm P-47 Prop on 4S

80A
1184 Watts
50 mph pitch speed

(5) Turnigy 350kv 4250 Motor on 6S with 1700mm prop (assuming that it doesn't fry)

86A
1909 Watts
57 mph Pitch speed

(6) Turnigy 350kv 4250 Motor on 6S with Skyraider 16x8 Prop (assuming that it doesn't fry)

63A
1398 Watts
50 mph Pitch speed


Conclusions

Looking over the data, there are a few viable options, almost all except option (2) which matches TiredIron's testing results (way too much current draw!). Almost all have descent pitch speed, and plenty of power. In flight the amps should drop a lot anyways when the prop unloads. The other systems might work as well, but will be pretty slow if the numbers are accurate. The best thing you can do is run it up while holding the tail. If it feels like it's not enough power, it probably isn't. Do a few practice takeoff runs, and check further before flying. Bottom line is flight test data. Test them and find out how they do in the air. Its really hard to predict these accurately, but these numbers will at least give you all someplace to start. I hope this has been at least partially helpful for choosing the appropriate power systems for our new Thunderbolts.

[F106DeltaDart]

On stock motor, ESC with 4S power and the 16" prop it pulls a max of 60A and 840W.

Awesome! That supports what you were saying earlier about the pitch looking more like 8". Makes a lot more sense by the numbers now.

[Aros]

So we're a go with the A-1 prop on 4S?

[TiredIronGRB]

Just flew it and it has very scale speed for rolls, loops and such but no speed demon (not much different than stock). I think the 580KV will work even better, the numbers above were of course a static pull on the table and it barely hit 60A. Balanced at 90mm with the 4S 5500mAh battery all the way forward (no tray) so I moved the battery back 10mm and now it balances at 93mm which feels good and needs very little down elevator when inverted.

I don't think the stock motor will handle 6S, it just does seem as solid as the older FMS motors.

[F106DeltaDart]

Just flew it and it has very scale speed for rolls, loops and such but no speed demon (not much different than stock). I think the 580KV will work even better, the numbers above were of course a static pull on the table and it barely hit 60A. Balanced at 90mm with the 4S 5500mAh battery all the way forward (no tray) so I moved the battery back 10mm and now it balances at 93mm which feels good and needs very little down elevator when inverted.

Great to hear TI! Eagerly awaiting mine to show up now, I plan on trying 4S with the 1700 prop and upgraded ESC.

[TiredIronGRB]

Great to hear TI! Eagerly awaiting mine to show up now, I plan on trying 4S with the 1700 prop and upgraded ESC.

I put my 1700mm Corsair prop on mine and it looks too big.

[F106DeltaDart]

I put my 1700mm Corsair prop on mine and it looks too big.

Scale diameter is between 17-18 inches for the P-47, depending on the model. Is there not enough ground clearance?

[AkumaZeto]

I have one of these NIB for 200 bucks you pay shipping check my for sale thread.

[OV10]

I responded over on the other post in the classifieds

[TiredIronGRB]

There's enough ground clearance it just doesn't look right and the hub is massive compared to the engine.

I got in three more flights and I'm really liking it.