Novak GTB/3.5 Lack of power?

[Neil153]

Hi All,

First post and I'm already after some advice! I have a Novak GTB with 3.5 motor that I recently took out my TRF415 and put into a Dark Impact (DI is fully hopped up including slipper clutch, front one way and ball diff). Whilst in TRF the motor was very quick as expected but after moving to the DI the performance has dropped off completely, from a standing start with full throttle it should light the tires and be off, but it just gradually accelerate away with no wheel spin at all. The strange thing is though when I put if in reverse it the rear tires light up, susupension compresses and she's off (in two wheel drive due to one way).

I've changed the profiles to remove reverse, and it's still the same. When I bench test it, she will quite happily hit full power (forward) and nearly pull the tires off their wheels (all wheels off the ground so no load on motor).

If anyone can help with fault finding or even if just to say I've damaged the motor I would be grateful. :teacher:

Many Thanks in anticipation.

Best Regards

[chilledoutuk]

well the 3.5 is a very high KV motor i would expect you should need to run a pretty small pinion to get the best out of it on the DI.

What pinion/spur are you running on your Dark Impact?

[kufman]

Novak doesn't recommend the 3.5 for anything but onroad. If will be very hard to gear for a 4wd offroader.

http://teamnovak.com/tech_info/brushless/br_gearing.html

[Neil153]

Many thanks for the quick replies, just ordered a MM/5700Kv to go in the DI. Gonna pop the 3.5 back into the TRF.

I think I was running a 24 pin and 87 spur.

Thanks again:wave:

[ElectricThunder]

I don't know the gear box ratio or the diffs' ratios, but I'd take a gander and say that may be too high.

Also consider, the DI tires/wheels are heavier and of a larger diameter than the TRF wheels. Combine that with what I think (don't have a DI, so I can't say for sure) is too much gearing for a 3.5, and that may be your problem.

That, or you programmed it all backwards after putting it into the DI (if you reprogrammed it).

[Neil153]

Electric Thunder. Thanks for your reply. I'm going to move the 3.5 back into the TRF on a 16t pinion. As mentioned I've got a MM/5700kv on the way and I'm going to buy a range of pinions (17-24) to see what suits it best. Time will tell.

Is there anywhere on the web where people have posted this type of information. A big data base of cars motors and pinions, that would be most helpful if so?

[ElectricThunder]

You can check in the vehicle forums on the main page. There may be some valuable information for your specific cars.

[chilledoutuk]

i would look into picking up a slipper for the dark impact if your going to run a mamba max 5700 as it will put a lot of strain on your diffs otherwise.

[SpEEdyBL]

May I ask what batteries you are using? If your not using lipo or the very best ni-mh packs, it is very easy to get sluggish performance with such a low turn motor without it being a gearing problem. As long as you can gear 15:1 with the 3.5r, you shouldn't have a problem.

[Neil153]

Thankyou to all for replying.

ElectricThunder - Will trawl through and find what I can, thanks for pointing me in the right direction.

ChilledoutUK - The DI is fairly hopped up, with everything from CF chassis to ball diffs etc so will hopefully be ok for now. Waiting on a new Durga, so may well transfer MM to it once I get things set up/hopped up ok.

SpEEdyBL - I'm running IB4200 with the 3.5 but have some 3C Lipos for the MM. Will probably use either depending weather I'm racing or bashing. I think my gearing has been the main problem from what I'm learning on the forum. I had a Novak 5.5 in prior to the 3.5 and that was fine with my gearing. I really need to learn more on gearing to get the best of things!

Again many thanks to all for your on going help.

Best Regards:wave:

[GSMnow]

Your pinion should scale pretty close to the number of turns. So if you were running a 22 (picked for easy math, 4 x turns) on the 5.5, you should start at roughly a 14 tooth on a 3.5 for about the same power draw off the batteries. It should give similar speed and more acceleration. Due to lower efficiency as rev climb and turns drop, you will probably need to go up a little from there. A 15 would be about the same speed, and a 16 should be a bit faster with maybe a tick more acceleration available still, but at more current. No free lunch, more power out needs more power in. Low turn motors get very hard on the batteries. They need more current just to make the same power, and they do it at less torque and more rpm.
Just look at the KV's
3.5 = 10,500
5.5 = 7,400
Here is teeth per volt hitting the spur
7400 x 22 = 162,800
10,500 x 15 = 157,500 a hair slower
10,500 x 16 = 168,000 a little bit faster

Hope this helps

[bassguitar]

I've got a MM5700 in my DI. It's a rocket but still controllable. You'll be happy with that I'm sure.

[Neil153]

Thanks to all for replying on this, I think I've discovered why the 3.5r was not performing as expected.
I some how over tightend both gear box lids on the DI which must have restricted the rotation of the the gears causing extra drag etc. I've backed off the lids on both gearboxs now and with no motor in she rolls forward and backwards just as you would expect and

Guess it was me being a bit ham fisted, you live and learn!

Thanks again:wave:

Neil