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Nov 19, 2015, 04:19 PM
Lazy Builder
Thread OP
Discussion

EDF Powered Pinewood Derby Car


Hello All!

A friend of mine and I have won the last two years at my universities "Open Class" pinewood derby (this means anything goes but combustion). We have done it with an GWS EDF-55 with an eflite park 370 5400 kv inrunner motor, and a 3S 1000 mAh 90 C discharge battery.

My question for the forum is how do we go faster?
I bought a 3S 350 mAh, 65-130 C discharge battery (also, two 2S of the same to put into series for a 4S). Is there a better motor that could drop into a GWS EDF-55?

Any thoughts would be appreciated!
Thanks,
Joe
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Nov 19, 2015, 05:03 PM
Do it Right, the first time!
CoolerByTheLake's Avatar
I think the question should be?----- Are you using a intake ring, and what if any thrust tube are you using? If so . what dia is the exit dia?
Nov 19, 2015, 05:49 PM
Classic jets rule
AIR SALLY's Avatar
C/N did one of these years ago and won with his too.
Nov 20, 2015, 12:28 AM
Lazy Builder
Thread OP
Last years model didn't have any inlet or outlet other than the EDF case. I'm not sure how to embed videos in a post so I went this route, youtube:
"Open Class" Pinewood Derby 2014 (0 min 13 sec)
Nov 21, 2015, 07:24 PM
Calm before the storm
Flyboy81's Avatar
Inlet ring and exit tube would help efflux speed for sure. I have an Great Planes Evader and it runs a 56mm Hyperflow fan unit exit diameter is roughly 44mm
Nov 22, 2015, 05:58 AM
The best in EDF since 2005
Extreme_RC's Avatar
EDF55 has inlet molded into the housing so no issues there, exhaust cone would definitely help.

I have supplied a few very hot 70mm fans for drag car guys down here, one got fastest time in the country, I don't recall the results but it was bloody fast!
Latest blog entry: Extreme RC AUSTRALIA
Nov 22, 2015, 02:37 PM
efflux RC's Avatar
This sounds like fun!
About 15 years ago me and 3 other dad's did some HO scale drag racing on 20ft drag strip set up in one guys garage. I still have my unbeaten "Barbie 1" corvette drag here some where. I'll post a pic if I can find later.

This should work great, and take the title. Hopefully the competition isn't reading this.... Ha ha.

Wemotec 50mm Micro fan
HET 4800kv motor
ZTW 40A ESC
Tiny 4ch rx.
Reduced FSA thrust tube for speed. works best 4-5 blade fans.
This is a 4s setup. I'd run a 4s, 30C, 900mAh (maybe smaller)for your drag race.
It flew my modified 50mm Katana quite fast.


If you want it as, you can have it for $75 shipped USPS Priority to contUS.

PM me for more info. I'll be in an out, so my reply might take a while.
There are some tiny dings in the rotor but it runs great. Maybe I'll file them lean for you if you can use use it.
I can post a pic (or email) the entire setup as it is if your interested

Whatever you decide. Have fun. Hope you guys win!

Gary
Last edited by efflux RC; Nov 22, 2015 at 02:43 PM.
Nov 22, 2015, 03:46 PM
The best in EDF since 2005
Extreme_RC's Avatar
Quote:
Originally Posted by The_Red_Baron View Post
Hello All!
My question for the forum is how do we go faster?
Is there a better motor that could drop into a GWS EDF-55?
Any thoughts would be appreciated!
Thanks,
Joe
Have you tried making a vertical thrust stand for testing your little fans? A piece of MDF with a hole cut out so the fan just fits in, and some dowel legs, bluetack them down to a digital scale and blutack the fan into the hole, I started testing GWS fans this way 10+ years ago. 5400Kv is quite a hot motor even for the EDF55, my setup for EDF55 & 64 is a custom made 24mm inrunner the ERC2445, 3750Kv and on 4 cells is pushing 850g thrust at around 32-33 amps. For short term running you could go to 5s, a little 1000mah 5s pack wont hurt you that much with weight, but your peak thrust for those few seconds of run time will be huge.
Latest blog entry: Extreme RC AUSTRALIA
Nov 23, 2015, 08:41 AM
Dont forget the velcro straps
corsair nut's Avatar
I did one with a 64mm edf rotor on the back setup as a pusher. smoked everybody hahaha. there was some guy with a 64mm fan strapped to the top and his kept flipping over from the tq.
Nov 23, 2015, 11:07 AM
Lazy Builder
Thread OP
These are some great ideas! Efflux RC, that is a tempting offer (PM sent).
I'm planning on measuring thrust with my own load cell (full wheatstone bridge on a cantilevered beam, calibrated to known weights.) What is the concensus on exit area for a thrust cone? 70%, 80%, 90%?
Extreme_RC, ERC's website appears to be down. Is there another place to purchase the ERC2445 or an equivalent motor?
Thanks again for all of the help!
Nov 23, 2015, 03:29 PM
efflux RC's Avatar
Quote:
Originally Posted by The_Red_Baron View Post
These are some great ideas! Efflux RC, that is a tempting offer (PM sent).
I'm planning on measuring thrust with my own load cell (full wheatstone bridge on a cantilevered beam, calibrated to known weights.) What is the concensus on exit area for a thrust cone? 70%, 80%, 90%?
Extreme_RC, ERC's website appears to be down. Is there another place to purchase the ERC2445 or an equivalent motor?
Thanks again for all of the help!
I only dealt with the HET motors in the 24mm size. The motor in mine is 4800 and is for the Wemo 50mm 4 blade fan, on 4s max. I have no info on ERC motors.
Keep in mind that the Wemotec fan does not have and inlet ring. You might need to fab something there.
I took some pics to email you.
As I mentioned in the PM with such a short distance to run, You want acceleration not top end, so actully no thrust tube reduction or very litttle reduction might be better. You just need to experiment with actual running.
Latest blog entry: Updated blog - Oct 2017
Nov 23, 2015, 04:18 PM
The best in EDF since 2005
Extreme_RC's Avatar
Quote:
Originally Posted by The_Red_Baron View Post
I'm planning on measuring thrust with my own load cell (full wheatstone bridge on a cantilevered beam, calibrated to known weights.) What is the concensus on exit area for a thrust cone? 70%, 80%, 90%?
Extreme_RC, ERC's website appears to be down. Is there another place to purchase the ERC2445 or an equivalent motor?
Thanks again for all of the help!
Website is running normal, here is the link to the inrunners:
http://www.extremerc.com.au/estore/i...ex&cPath=46_98

I been doing wemotec microfan setups for 8 years now, good little fan that can produce high thrust with enough power behind it but you will definitely have to fabricate an inlet lip or you will lose much of that performance. Personally for what you are doing I would try pushing your GWS fan harder first, lower Kv motor like the ERC2445 with more cells will get you a burst situation that is favourable for drag racing.
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Feb 03, 2016, 05:44 PM
Lazy Builder
Thread OP
Well the school / fun project was completed. Turns out, for static thrust only, a straight duct is a liability and a tapered duct is comparable to no duct at all. The highest RPM I saw was 41000 RPM (I am at 4,400 ft altitude). The highest thrust was 460 grams (though I think without a duct, I could have gotten higher with the same RPMs). See the pdf attached.

I'm really tempted to put a 4 cell lipo on here, but I'm afraid I might fry the motor. Any thoughts or data? It will only be at full throttle for 2 seconds tops.
Last edited by The_Red_Baron; Feb 03, 2016 at 06:05 PM.
Feb 03, 2016, 07:06 PM
The best in EDF since 2005
Extreme_RC's Avatar
You should be able to get away with 4s for the short bursts you are doing, especially at your height where you are losing thrust anyway and your amp draw is not too bad.

Here is the original chart I did for the GWS fans, its accurate for almost sea level. I was going to expand the chart to incorporate the later test figures that took the EDF64 over 1 kilo in thrust but never got round to it

You can find some of my old GWS data HERE
Latest blog entry: Extreme RC AUSTRALIA
Feb 11, 2016, 11:17 AM
Lazy Builder
Thread OP
That's crazy to see how much the density of air affects thrust. Thanks for the info.

So far we have three cars with three different motors:
Himax 2025 5300kv (from an old Alfa Mig that met an unfortunate end)
http://www.radicalrc.com/item/Himax-...t-Drive-104892

Eflite Park 370 5400kv (as listed above)

HK 2040 4800kv (I have no experience with this motor. It was the only one that would fit our set-up in the USA west warehouse)
https://www.hobbyking.com/hobbyking/s...arehouse_.html

Any thoughts on each of these running a 4S in a GWS EDF 55?


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