Official Black Horse 1724mm Dornier DO335 Pfeil ("Arrow") Thread

[Oxotnik]

Nick, when I decided on the Spitty 5055-390kv motor, it was based on me liking the SK3 5055-430 (which I can't get at the moment) with 14x8x3 props for the 17 1b A-26. I'd have no qualms running that power train again for the 335. As the 335 will significantly lighter and less draggy than the A-26, that power train should do well for the 335. Plus, this power train was no pulling near the wattage that the motor could handle. Unfortunatley, the SK3 5055-430 wasn't available and the next closest I could find in that size class and kv was the Spitty 5055-390. But, increasing two inches in prop diameter should result in a power increase (intuitive assumption, based on one data point). It does concern me that the Spitty is running this motor with a 16x10x4 prop; so, by dropping a blade, I'll be giving up some power per motor. But, I'm doubling up the motors. So, again, in the absence of experimental data, I expect the power of the motor with the MAS 16x10x3 prop to be good for the 335. One day this week, I'll put the 5055-390 and MAS 16x10x3 on a wattmeter to see what it actually does. if I were to decide to go down an inch in diameter, I believe that the power output would still be good. I'll also put a MAS 15x9x3 on the motor and see what the wattmeter says. Unfortunately, I stopped by my LHS today, hoping to pick up a pusher MAS 15x9x3, but they didn't have any in stock. I hope that MAS offer a pusher 15x9x3; I haven't checked yet.

Another set back... My LHS had some TruTurn spinners on the shelf. I grabbed a 3.5" 3-blader spinner, which fits very nicely on the MAS 16x10x3 Tractor Prop, but very unfortunately, the friggin prop shaft on the Spitty 5055 is too friggin short for the spinner/prop. UGH! If it weren't for bad luck, I'd have not luck at all. Gloom, despair, and agony on me.

[MANFRED]

You could probably source a longer prop adaptor

[Oxotnik]

You could probably source a longer prop adaptor

Yeah, I was thinking that I may need to find a local machine shop and have them cut me two adapters with the same 3mm hole pattern and a longer 8mmx1.25mm prop shaft.

[edit] Found a solution!!! The prop adapter for the FlightLine Corsair's 5055-320 motor fits on the the Spitty's 5055-390 motor. This adapter a thicker prop shaft (it looks like 10mm to me, versus the Spitty's 5055' 8mm shaft), but it is significantly longer, too. I'll have to drill out the TruTurn backplate to 11mm or 12mm (to go over the hex 'nut' at the aft end of the prop shart) and ream out the MAS 16" prop to 10mm, but it'll work. Now, to order a couple F4U prop adapters from Motion. I like simple solutions. LOL

[handyman220]

Corsair 5055-320??? Hope you mean 5055-340. Following you closely Oxotnik, I need all the professional help I can get on this one! Waiting to see what props you come up with before I order anything.

[Oxotnik]

Corsair 5055-320??? Hope you mean 5055-340. Following you closely Oxotnik, I need all the professional help I can get on this one! Waiting to see what props you come up with before I order anything.

Yep, the Corsair 5055 is 340kv. My bad. Sorry.

I'm just fumbling my way though this. I'm making it up as I go. When I put the motors and props on the wattmeter, then I'll have some good info to report, instead of just supposition and intuition.

[Creative RC]

I ran the RimFire 1.2 (450kv) in ecalc and it turns the 16x10x3 quite well and with a lot of thrust, maybe even too much with two motors. Maybe that motor in the front and a smaller motor at the rear. It weighs 400 grams, just a bit less than the 5055 motor. But when putting it on 5s or simulating less throttle it talks about pitch speed should be double stall speed.

With two props of the same size and pitch, would the rear motor and propeller be working less hard (using less amps) due to being fed air (pressure) from the front propeller. If that is the case, maybe the one in the rear could get away with a higher pitch. For example a 16x8x3 in the front and a 16x10x3 at the rear. It would be an interesting experiment.

Interestingly, the fellow in the video with his 4s setup using the same Turnigy SK3 4250740 with 13x8x3 props was getting 57 Amps on his front motor and 45 Amps on the rear motor. He thought it might be on account of the long power cable to the rear but I suspect not.that alone.

[OV10]

Yeah, I was thinking that I may need to find a local machine shop and have them cut me two adapters with the same 3mm hole pattern and a longer 8mmx1.25mm prop shaft.

[edit] Found a solution!!! The prop adapter for the FlightLine Corsair's 5055-320 motor fits on the the Spitty's 5055-390 motor. This adapter a thicker prop shaft (it looks like 10mm to me, versus the Spitty's 5055' 8mm shaft), but it is significantly longer, too. I'll have to drill out the TruTurn backplate to 11mm or 12mm (to go over the hex 'nut' at the aft end of the prop shart) and ream out the MAS 16" prop to 10mm, but it'll work. Now, to order a couple F4U prop adapters from Motion. I like simple solutions. LOL

I knew ya would work it out, was just sitting in the wings and was gonna give ya a day before suggesting the same to ya

[Oxotnik]

I knew ya would work it out, was just sitting in the wings and was gonna give ya a day before suggesting the same to ya

Thanks, Pa. I feel all grown up now.

[OV10]

[Oxotnik]

Okay, I've got some bench test numbers for the Spitty 5055-390kv motor and MAS 16x10x3 prop.

Configuration:
Motor: Freewing 5055-390kv
Prop: MAS 16x10x3 prop (tractor)
ESC: Hobbywing Skywalker 80A
Battery: CNHL 6S-5AH, 70C, full charge

Results (about 10 seconds at WOT):
Current: 56.6 Amps
Power: 1345 Watts

Power/mass (assuming that the AUW is 13.5 lbs, and that the same config is run for both the tractor and pusher power trains) = 2*(1345W)/(13.5 lb) = 199.3 Watts/lb


I was a bit surprised at lowish value of the current draw, but at 199 Watts/lb, this dual power train should work well for the 335, but it won't be a speed demon. For those considering a Power 60 class electric motor and 16x10x3 prop, I'd encourage to maybe look for a motor with a bit higher kv. I believe that the recommended Admiral 5045 (IIRC) motor has a higher kv. Having not already invested in these Spitty 5055=390s, I might have gone with the higher Kv Admirals.

But, on the up side, the underperformance (in regard to power draw) probably means longer flight times....

[OV10]

The recommended Admiral 5030-400kV is only 10kV more than the Spitty motor but here is where the real point that you're missing is Chuck.
The Admiral has only a 1180W rating. The Spitty spanked that by 200 watts and didn't even come close to its max of 1950W.
The spec on the 5055-390kV Spitty motor product page for max wattage still hasn't been corrected .........reads 950W(confirmed to be incorrect 2 years ago by Alpha)
So the watts that you tested out is approx. the same as I got almost 2 years ago when I tested for the A-26.
Now then……….. you are getting power that is on the verge of 3D power for $30 per motor less expensive...………. I say that is a win

[Oxotnik]

Okay, Charlie, I was thinking that the Admiral 5030 was closer to 500kv. 200 W/lb is very respectible, no doubt. I stopped by my LHS again today (BTW, they offered to make me a cot in the backroom, since I seem to be there every day or so.... LOL). I found an 8mm EFlite prop adapter with the same hole pattern as the Freewing 5055s, but the prop shaft is about 3/4" longer. It's the prop adapter for the 1.3m EFlite Extra 300 (EFL 11595), In case anyone is interested.

This morning, I drilled out the back plate of the TruTurn backplate to 12mm (to fit over the hex 'nut' at the base of the prop adapter (from the Corsair's 5055-340 motor) and reamed the MAS prop out to 10mm. Used a star lock washer between the backplate and the prop adapter (to keep the aluminum-to-aluminum surfaces from sliding) and put a 10mm washer between the prop and the prop nut, and everything tightened down nicely. The prop nut takes a 3mm screw to attach the spinner to the rest of the prop assembly. Unfortunately, the TruTurn spinner is long and I couldn't find a 3mm screw long enough to reach it (that long would probably be too long for a 3mm screw anyway). So, next step - drill and tap the prop nut for the 5mm screw that comes with the TruTurn spinner. Since I got the TruTurn spinner to work for the tractor motor, I need to order a TruTurn for the pusher motor/prop. Since I'll be ordering it, I'll have TruTurn anodize it black. I'll have to paint the shiny alumimum tractor TruTurn spinner that I already have.

So, now everyone is caught up on my Pfeil shenanigans (maybe, I should start calling them 'Pfeilnagigans'... :-) ) for the day.

Charlie, good call on the Spitty 5055s. They're taking a bit of work for this application, but they're going to work out very nicely in the end. No pain, no gain, right?

[OV10]

Chuck, speaking of good calls, that Eflite prop adapter find is awesome.
I just printed this page to put with my reference tech data for future use.
Why hog out a spinner back plate for a hex shaft if ya don't have to

edit ………. just looked at the pic of that EF prop shaft.
I assumed that it had a smooth shaft but not so.
But is still a good scavenge.
Here's a direct HH link to the EFL11595

[OV10]

Here's what the FL Corsair prop adapter looks like for those that want a visual comparison.
ps………..the EF is $4.99 and the FL is $6.99

[downwind3zero]

I get 2x 6S 5000 in without difficulties. The aft one sits on the upper deck which might need some reinforcement, but it will fit and it is right over the CG.

[Twowingtj]

downwind3zero That looks like a good solution! Helps keep the ESC wires to the rear a little shorter too.

[Oxotnik]

I get 2x 6S 5000 in without difficulties. The aft one sits on the upper deck which might need some reinforcement, but it will fit and it is right over the CG.

I'd thought about that as well, but decided against it because that weight would be behind the CG. How does yours balance? Did you have to add any nosewheight? What kind of platform did you build to support the battery?

After work today, I've had the soldering machine going strong. For the pusher ESC, I decided to put the ESC in the servo bay and lengthen the three-phase wires running from the ESC to the motor. I also made a custom parallel harness, assuming that the 6S-8AH battery (which I ordered last night) sits in the forward battery compartment with one ESC and the other ESC is in the Servo Compartment.

[downwind3zero]

Oxotnik I don't know for sure how it will play out but the battery in that position is almost CG neutral. The CG projects to the front edge of the hatch and the battery is almost centered. I have only trialed the fit not balanced yet, but I plan on using a Tru-Turn in the front which will add some weight. We'll see.

[MANFRED]

If you are going to use 2x 6s, why bot use like a 3400mah for each motor. Still would be more mad than 2 motors splitting a 5000mah and alot less weight

[Oxotnik]

If you are going to use 2x 6s, why bot use like a 3400mah for each motor. Still would be more mad than 2 motors splitting a 5000mah and alot less weight

I'm not understanding the point you're trying to make. How would 2x 6S-3400s be lighter than a single 6S-5000? Did you mistype something?