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Need new motors? Grind a gearbox? Adding teeth to a pinion?
User avatar
By Jkaz870
#149225
I bought 2 of these from amazon(link below). Watched all the vids on the wiring. Put the heat sinks on the stock motors. My son (40 lbs) blew a motor after about 1 day of light use.

I dont want to get too crazy with upgrades. Is there a cheapish and easy solution to upgrade the motors so they dont fry?

ExpertPower EXP12180 12 Volt 18 Ah Rechargeable Battery with Nuts and Bolts
Last edited by Jkaz870 on Sun Jun 17, 2018 7:39 pm, edited 2 times in total.


User avatar
By toycrusher
#149251
visit eastcoastpowerup for an ESC kit. Or, buy lots of spare gearboxes :lol:
User avatar
By Hammer-fm
#149262
ESC has soft start and also limits current. Running the stock motors at 24V creates a lot of current draw and instantaneous (at startup) torque which tears up the gears. With soft start the motors can take up the gearbox slack before the full torque hits.

That said, even with an ESC the stock motors will not last at 24V. You can upgrade to a 775 (larger case) motor and it will last longer, though no guarantee it won't need replacing in 3-6 months (better than one day). You can try the cheap ones on this thread (w/16T aftermarket pinions).
User avatar
By Jkaz870
#149274
Hammer-fm wrote:ESC has soft start and also limits current. Running the stock motors at 24V creates a lot of current draw and instantaneous (at startup) torque which tears up the gears. With soft start the motors can take up the gearbox slack before the full torque hits.

That said, even with an ESC the stock motors will not last at 24V. You can upgrade to a 775 (larger case) motor and it will last longer, though no guarantee it won't need replacing in 3-6 months (better than one day). You can try the cheap ones on this thread (w/16T aftermarket pinions).
Thanks, I did grab some traxxas 775s to try, hopefully they will last. I plan on monitoring the temp with a bbq thermometer. If I can get it to work I'll post pics. If heat is an issue I may get a couple DC motor speed controllers and go that route.
User avatar
By Hammer-fm
#149276
Running those at 24V without an ESC will almost certainly break the gearboxes in short order -- see my replies in this thread and the eventual outcome. The motors pull a lot of current at startup and (as a consequence) also have a lot of torque, so even with 'minimal' mechanical advantage (23T main pinion), they're likely to break a gearbox. You're going to be running 16T gears -- it's probably 50-70% more torque than stock @ 24V.

They may last on pavement if the tires are still "low-traction".

18V will work better -- but requires mix-and-match (6v/12v) batteries. An ESC limits the maximum current draw and (thus) torque, and will limit it to ~stock or lower levels.
User avatar
By Jkaz870
#149459
Today my son was on it and it started smelling like burning. Im assuming the traxxas wont last much longer. If i bought a bunch of the Jameco 775s you suggested in your post would those hold up under 24v for any length of time? I can get about 16 of them for the price of 2 traxxas...
User avatar
By Hammer-fm
#149460
Not sure. I am running two of them at 22V on one of the Hurricanes, but it has a fairly weak speed/current limiter (similar 'protection' effects as an ESC). That Hurricane did eat up one of the Banebots 18V ones (running at 22V also), after 30-40 minutes of two 4th graders driving it -- so probably depends a bit on how it's loaded. That had survived six+ months of driving before that incident.

So I'd say that 24V is definitely pushing it, but probably not any more than on the Traxxis motors. It's possible that they'll run longer and be more durable. I don't have enough technical information on the Traxxis ones to really know...
User avatar
By Jkaz870
#149461
Cool thanks for the info. Am I still ok to run the 16t pinion? Im a little lost on gearing.

The Jameco ordering is pretty strange. You can get 2-4 for like $30 or get 16-17 for $50... I may just stock up on them and replace them as needed or sell them to others in need. We have an artic cat pw too that my 3 year old drives but he doesnt need any more speed till next year.
User avatar
By Hammer-fm
#149485
If your gearbox is a 15/16/17T (which is what the stock Dune Racer ones are), then yes -- a 16T standard pinion is the right fit.

The best way to get 4 is to get the Jameco listing on ebay, eg:
https://www.ebay.com/itm/Nichibo-Taiwan ... m570.l1313

4 for $15.80 shipped.

If you're buying larger quantities, then ordering directly from Jameco.com is better. I have about 20 sitting in my garage too... spares are good, although at the rate I'm burning them up right now (0 in the last year)... maybe I won't ever need spares :lol: .
User avatar
By Hammer-fm
#149525
Wesley - That's not accurate as far as I can tell. Which spec are you using?

Stock PW motor is 15.7 RPM at 12V, 400mN*m torque (Johnson 683LG-001)
775-7013F is 15.5k RPM at 12V, 533mN*m torque. Jameco Datasheet

In all of the applications I've done the speed difference relative to the stock motor (given the same voltage) is negligible, including a straight motor-only swap I did on Sunday on a 19T gearbox that I'd installed in a Hurricane. It's definitely not 35% slower.
User avatar
By Hammer-fm
#149574
I realized the confusion may be that Jameco 'advertises' the Max-efficiency RPM ("12VDC Motor 12,610 RPM" is the title) . That would look like 1050kV. The posted data sheet shows the no-load RPM which is what we're typically comparing, and personal experience on multiple vehicles suggests the data sheet is fairly accurate.
User avatar
By Hammer-fm
#149586
I've gotten them from Mltoys (they sell both empty gearboxes and gearboxes with gears, with or without motors), and there are a few listings on ebay from another vendor as well. You can buy a "18-19-20T w/solid axle", and use your existing gears in it. You will need to drill out the axle hole. I used a step bit and drill press to make sure it was centered. I'm not sure how well it will work if trying to do it by hand. Buy 19T pinions for the motors.

Or you can buy a "21-22-23T" one and that requires a 22T pinion for the motor. Lower torque but more speed. At 24V with the 22T setup the Nichibos will go very fast -- probably 2.5x stock, which is (IMHO) too fast to be really controllable without a speed controller/ESC. 18V on a 19T or 22T setup is probably the optimal arrangement, but that means a 6V battery which is a bit annoying.

Are you running mostly on pavement? Have you added rubber to the tires or anything else that would increase the stress on the gearboxes?
User avatar
By Jkaz870
#149589
Hammer-fm wrote:I've gotten them from Mltoys (they sell both empty gearboxes and gearboxes with gears, with or without motors), and there are a few listings on ebay from another vendor as well. You can buy a "18-19-20T w/solid axle", and use your existing gears in it. You will need to drill out the axle hole. I used a step bit and drill press to make sure it was centered. I'm not sure how well it will work if trying to do it by hand. Buy 19T pinions for the motors.

Or you can buy a "21-22-23T" one and that requires a 22T pinion for the motor. Lower torque but more speed. At 24V with the 22T setup the Nichibos will go very fast -- probably 2.5x stock, which is (IMHO) too fast to be really controllable without a speed controller/ESC. 18V on a 19T or 22T setup is probably the optimal arrangement, but that means a 6V battery which is a bit annoying.

Are you running mostly on pavement? Have you added rubber to the tires or anything else that would increase the stress on the gearboxes?
No pavement, tires are just stock plastic no mods for traction. Basically all flat open grass maybe 3-4 acre front yard.
User avatar
By GrandpaChar
#149663
I have a 24v Duneracer with the Eastcoastpowerup ESC that works very well.

I spent quite a bit at other parts houses looking for gears that would hold up and as soon as I put this into the car it has handled the power without breaking stuff up.

If it were not for my neglecting to grease one of the main gear shafts after the first gear went away prior to installing this kit, I believe this would have continued running flawlessly.

The driver is a rambunctious 4 year old boy.
User avatar
By wesleyb82
#149668
Hammer-fm wrote: Stock PW motor is 15.7 RPM at 12V, 400mN*m torque (Johnson 683LG-001)
775-7013F is 15.5k RPM at 12V, 533mN*m torque. Jameco Datasheet
I just measured the 775-7013F and the no load speed is 1200Kv which is about the speed of common 775s like the 18v Banebots but this is slower than the factory 550s which are 1400Kv. Just wanted to point that out in case there is someone involved in a race or the like that is looking for every possible advantage.
User avatar
By Hammer-fm
#149670
Thanks Wesley -- good point that not everyone wants the 'budget' alternative as you do give up something. I hadn't previously done exacting measurements.

What have your measurements indicated for typical stock motors? They spec out at 1300kV (15700/12), not 1400 -- but that's assuming the Johnson 683LG-001 is really the model being used here. The 8514 Banebots motor is 19500 RPM @ 18V, which is 1080 kV. So the Nichibo would seem to split the difference. I don't know how often the manufacturer specs end up being "close" and how often they're effectively made up. These seemed to be reasonable/close, but "eyeballing" the vehicle speed is difficult, and at this point none of them are stock enough to really compare directly very easily.
.

I'm curious whether you got the flat-nose 775-7013F (with large vents) or the cone-nosed ones (with smaller vents). I got one shipment of the flat-nose ones first; my second shipment was cone-nosed ones, and the third order was all flat-nosed. The cone-nosed ones have a lower no-load current draw (1.65A vs. ~2.2A for the flat-nose). I don't have a measurement methodology that will directly measure winding resistance accurately enough to tell the difference, and didn't have one that isn't installed somewhere at the moment, or I could have added it to my experiment.

Speaking of... I decided I'd try to measure a few. I don't have any 'official' motor tester, so I came up with something else that should be quite accurate (+/- 2%) . I used a brand new 15-16-17T gearbox and a few different motors. I used a clear indicator on the output gear and took 30fps video (25-30s of runtime), extracted exactly 20s (600 frames) of it, and counted how many revolutions the indicator made. I can do this frame-by-frame and get within ~1/5 of a revolution without a lot of extra focus. I also measured voltage at the motor and current from the supply (I was using an XBOX 360 12A 12V supply).

[attachment=0]measurement_method.gif[/attachment]

Those measurements do indicate the 7013F is slower -- the two new ones I tested are about 5% slower than spec -- making them 6-7% slower than stock. I did get 1250kV, rather than 1200. Sample-to-sample consistency is about what I'd expect, though I expect even more variation if I did 10 of the 7013F motors.

The stock FP ones (from brand-new gearboxes) were basically within expected tolerances (1300 +/- a few %), and the used one -- from a Craigslist F150 that had gone through at least one set of tires -- was also spot-on. The (used) Mabuchi 8514 was noticeably faster than spec.

I was glad to see the KC3SFN-8021F Jameco special ($2.50 each) landed right on spec at 23000 RPM, which backs up my original measurements (done in a similar fashion, but in-car using marks on the wheels with it off the ground), which were also taken with the Corvette motor at that time and I'd estimated a 15-20% speed increase (15% measured here) between the two.

Generally the no-load current I saw with the motor standalone (eg. not attached to the gearbox) is about 10% lower. The drag from the gearbox really isn't too bad, and that also indicates that the motor is spinning [u]very [/u]close to its "free" RPM (current draw will linearly ramp to the stall value as RPM goes to 0). Put another way, the 7013F I measured at 2.2A free, and 2.4A here, with the gearbox attached. The 200mA increase can be used to infer the RPM difference between gearbox attached (extra friction/load) vs free. Using the 66A stall specification, we calculate it's going to at about 99.7% of the free RPM (1 - 0.2A / 66A stall). That's about 50RPM (which I can't measure :lol: ).

[attachment=1]motor_comparo.gif[/attachment]
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