M.L. Toys
M.L. Toys
HobbyMasters M.L. Toys
Need new motors? Grind a gearbox? Adding teeth to a pinion?

I have been a lurker for a few years newly created account and appreciate the help. I am posting for some guidance I hope someone may be able to help me and in future help someone else in the same situation.

We have a
Model: Jeep Hurricane X-6645
Gearbox: 7R Stock
Motors: Stock 15T
Battery: upgraded to 18v 20ah
Mods: Added 40amp Fuse on battery terminal - 30Amps would pop everytime, everything else stock
Pinion: 15T - Stock
Terrain: grassy/hilly (30deg at most) yard.
Rider: Son is 5yrs old and 44lbs, other son is almost two and wants to start riding with big brother

Goal: Not drop speed and either gain speed or torque for future growth

We have been running the stock everything on 18v for over a year but I think the stock motors are starting to fail

I just ordered the Nichibo Taiwan KC3SFN with the Robinson Racing 16T Pinions as backups when the stock motors die

Im second guessing myself and think If possible I should do one of the other following options and asking for maybe someone who has more experience.

Option 1:
Buy two new Gearboxes 21-22-23T gearboxes with 22T pinions and use the purchased Motors at 18v. Not sure if this is too much for the gear ratio to handle or motors with higher ratio

Option 2:
Buy higher torque motors with new 21-22-23T gearboxes since this gear ratio (I think will raise speed but lower Torque) and thus will equal out since the higher Teeth count automatically increases speed but new motors will have the torque?

Option 3:
New higher voltage motors with the new 21-22-23T gearboxes and run 18v to them? Maybe the 18v Banebots, etc

Option 4:
Listen to better options the community has and go with that plan


Thanks for the help

Interesting and good to know. Appreciate the response. Apparently I was incorrect in my thinking after reading the gearbox thread and thought that the 7R gearboxes were the same/interchangeable apart from the first gear T count and pinion on the motor had to match.

So to confirm, For our model there is not a way to change to gear ratios with matching Pinion count?

Ive lurked your website countless times but I guess I thought the only change in the 7R gearbox from the site was the first gear so I figured I could change that myself if needed.

Again thanks for all your information with this hobby
Untrue, if you're handy or have a buddy with a drill press.

You can take a 7R gearbox for the small axle and drill out the axle hole and run it on the Hurricane, including the 22T ones. I've done several 19T swaps (one Dune Racer and one on my Hurricane). I recommend a stepped drill bit and a press though.

As for your options: The KC3SFN motors are a lot (45%) faster than stock. I doubt they'll last long at 18V, and you will really overload them if you try to run them with a lower gear ratio (larger pinion). They're a really great "1st step upgrade" for people that just want to stay at 12V.

Since you've already been running with 18V, I'd recommend going to a 775 motor and a 19 or 22T setup if you want more speed. The Banebot 18V are a decent choice; the Jameco/Nichibo is nearly the same if you get lucky and get the "big window" version (there are two variants; one of them has smaller vents and is more prone to overheating at high loads). For $3, even the small window one is a bargain, and they ran for a long time in the Mustang (36V/dual-motor gearbox). On grass you may do better with the 19T, which will be a bit faster than your current one (it will definitely have more torque). The 7013F is a big faster (~8%) than the Banebots, but is still ~6% slower than a stock motor, but you're getting a 25% increase from the gearing so it will be noticeably quicker.

BTW, I'm impressed you got a year out of the stockers at 18V, especially on hills. I never had that kind of luck with mine -- torched one brand-new replacement in the first 45 minute session (after that it was all 775s).
Thanks hammer,

Your post in the motor thread sticky is what got me thinking about swapping in new gearbox/pinion count in the first place.

Well shoot, I ordered the KC3Ns already, so are they comparable running them at 12v with running stock at 18v then?

I could run the 19t gearboxes with those motors at 12v and still have a faster ratio and much longer run time. Hmm so many options.

If anything I'll have them as backups for when we have to buy another Jeep for our youngest son.

Since you've done this process did you rewire everything also or keep stock electrical?

I installed a voltage gauge yesterday and it reads 19.2v on stock motors so I'm also surprised if your surprised since you know alot more about this. I've just read they last awhile at 18v so assumed it was normal, :D

So for grass you'd recommend 19t with 18v/775, so I'm assuming since going to 22t we would lose too much torque for grass and 22t would be for more road flat surfaces?

So I'll need two 19t gearboxes, drilled out for axle size, motors and pinions. Do you happen to know the final axle size bit you've used?

Thanks for your help
Hi Rizzo,

The KC3SFNs at 12V are fairly close the stockers at 18V. You don't get as much starting torque but they also don't run as hot. I did some fairly precise measurements of them under ~no-load conditions (in a gearbox but outside of a vehicle) and their RPM runs right at their rating at 23k RPM, vs. 15.8-16.2k measured for stock. The 7013F motors run 14.9-15.1k (vs 15.5k spec), and the Banebots was 13.7k (vs 13k spec). What i haven't done is get great measurements for the torque. I did get some low-precision measurements but life got in the way of setting up anything more elaborate :lol: . It's probably within 10%, and what it said is that stock matches up pretty well with the spec -- ~60A theoretical stall current, ~400mNm of torque at 12V-- about 6.6mNm per amp of current. As expected, the KC3SFN with a shorter winding only puts out about 5.2mNm per amp, but the lower winding resistance means it has a hypothetical stall of ~102A @ 12V, so you could -- with an infinite current source -- actually make 525mNm. If I scale up to 18V, the stock motor should pull 90A and make 600mNm of torque.Since you'd run the KC3SFN with a 16T pinion, I'd say that you'd lose at 15%-20% torque by going back to the KC3SFN and running it at 12V (speed would basically be the same). All that isn't really super interesting for this vehicle since you already have 18V, but if you got a 2nd ride the KC3SFN are a good drop-in and it's *easy*.

Let's talk about the 775 motors :).

Neither the Nichibo 7013F and Banebots 18V measured up as well on torque-per-amp as I was hoping. The Banebots was 8mNm per amp (vs 9.35 spec) and the 7013F was 7.6 (vs. 8.2 spec). However, they're both still better than stock and the heat capacity and dissipation makes a substantial difference.

I plugged a few scenarios into my modeling spreadsheet; it doesn't do a good job modeling battery droop or winding saturation (the torque per amp falls off as you increase the current), but it's a good start.

For a Hurricane (~16" wheel, 15T gearbox), your level speed at 18V should be around 7.5mph. Starting torque at the wheels is around 90Nm.
Nichbio 7013F and a 19T gearbox at 18V: 8.5mph and starting torque of 100Nm.
Nichbio 7013F and a 22T gearbox at 18V: 9.9mph and starting torque of 87Nm.
Banebots 18 V and a 22T gearbox at 18V: 9.0mph and starting torque of 93Nm.

I'd ask 2 questions about whether to go to 22T or 19T:
(A) Is 10mph too fast without a speed controller or two-stage option (12V/18V switchable)?
(B) How capable was the previous setup at doing the hills?

If the previous vehicle was great even on the hills/grass, and you want to try out the higher speed, I'd go big and get the 22T. Buy a 4-pack of motors and you'll have spares to swap in if it is just too overloaded. But if you want a milder upgrade, il still get a bit of a speed boost and better hillclimb capability with the 19T and the 7013F.

Note that you'll be less likely to break the gearbox itself using the 22T since that produces less torque on all the internal components.

As for your other questions: Yes, I'd expect 19.3-19.4 on a freshly charged 18V system. I was surprised at your longevity because Hurricanes don't have great airflow around the motors. My failure was on a brand new 15T gearbox, being driven by a step-down (voltage) converter that was outputting 20.5V; we ran it pretty continuously with two kids (4 & 2 years old at the time) around our (not-level) cul-de-sac for about 45minutes and it spun 1st gear. The motor itself didn't fail, but it got hot enough to soften the plastic around the 1st gear shaft and it walked, destroying the gearbox. That same vehicle later burned a Banebots 18V but that was with two 4th graders riding in it, so you could argue that was an overload condition :lol:

Rewiring: the level of rewiring depends on the vehicle. The aforementioned Jeep was using 3x step-down converters and a 24V battery, but stock pedals and gearshifters. The F150 uses a homebuilt PWM controller, and uses the stock 'gas' pedal as a brake pedal (next to the hall-effect gas pedal) -- but it operates the same way (selects either the PWM controller, when not pushed, or shorts the motors out when depressed). One half of the gear shifter (forward-reverse) is used as in the stock configuration, but 1st-2nd was just a switch to limit the PWM controller's throttle.

The Mustang has relays to do the switching and retains zero of the old wiring, but again ... custom PWM controller there.

I don't personally worry too much about upgrading the factory 14g wiring by itself -- I feel like the limiter is more likely to be in the switches, so if you go to a rewire, you want to do one of the relay-based ones (good schematics around) and use 10-12g wire.

I don't know the final drill size I used. I had a decent step-down set and just mic'd the hole in the existing gearbox and drilled the new one to match. I had to go in from both sides since the step down bit isn't very deep (for each size). Unfortunately we just moved houses and all my PW stuff is packed "somewhere"... :lol:
Last edited by Hammer-fm on Fri Apr 05, 2019 9:38 am, edited 1 time in total.

I cannot thank you enough for the time you put into these responses. I also found your spreadsheet and am plugging some numbers in on some motors I have also found. If you don't mind me asking I would like the Mods to Sticky the Spreadsheet Calculator as its an easy way to plug and chug numbers for motor types to help people with the "is this motor better than this."

As an example Motor I found: ... e-motor-v2

Andy Mark 775 Redline 775a I have attached the spec sheet and a screenshot of the entered Information for that motor.

Seems like this is a 775 Series 12V (DF-30), which they also have an 18V (DF-15).
After putting them into the Spreadsheet using 18v on the 12v motor with a 19T Pinion, the peak torque @ takeoff is 121.2, while the Max Speed is 11.35MPH.

Does the Motor Torque Constant Measurement (mN*m/A) = starting torque? From this motor I gather ~54Nm?

Spec from Sheet:
Manufacturer & Model RedLine Any Mark DF-30
Spec Voltage 12
No-Load Speed (RPM) 21020
No-Load Current (Amps) 3.81
Stall Current (Amps) 130.12
Stall Torque (mN*m) 700
Max Efficiency Speed (RPM) 16866
Max Efficiency Current (Amps) 22.24
Max Efficiency Torque (mN*m) 100
Max Efficiency % ~71.4

Also, I see in your spreadsheet under Motor Database, that the Banebots you have labeled them as having too high of a stall current for standalone use. Im not sure what you were referring to in that regard. Is 130A too large without an ESC and will cause too much strain on the gears?

I also realized you have answered some of the same questions a few other times in different forum threads after searching for a few days different key words, again Thanks for re-answering some of the same questions

I will post those here for the next person searching the Jeep Hurricane and needing/wanting these in a single thread.

It looks like in the Dune Racer thread you used a 4-20mm Metric step bit:

Post# 149022

"Small case has a hole diameter of 0.490". The large case is 0.800". It's been awhile but I believe I used my 4-20mm metric step bit (20mm cuts a ~0.790" hole). US step bits will probably get you 3/4" -- 0.750" which is going to be a tight fit on the axle -- if you have a way to ream it out just a bit more that should do it. It's supposed to be a slightly loose fit, but going to something like 7/8" is going to be too large. "

I do have the 3/4" axle so Ill have to make sure I have not lost that bit in my set.

Every time I read a thread your thoughts/suggestions make me want to try something else, like the Quad Damage Mod. Seems fairly straight forward once getting the Aluminum mounted to the gearbox, marking and drilling the holes. I cant stop overthinking the best ways to do these upgrades.

As for current setup: The Jeep currently does Ok on hills but I think as the weight of my Son increases and add a friend/brother in there it wont make it without the additional Torque.

I do like the 19T due to the added torque so I think Im going with that option. I can always grab an empty 22 box down the road and get a pinion for testing/flat surface speed races against brothers. Plus the $3 Jameco I can burn those out without even worrying about cost
Andy Mark DF-30 12v.png
Andy Mark DF-30 12v.png (323.75 KiB) Viewed 666 times
Thanks for the kind words Rizzo. I have made some updates to the spreadsheet since I last posted it -- mostly in the motor database section.

The AndyMark motor looks nice and I'll add that one, although I'm not confident on longevity at 18V (32k RPM). Vex Robotics makes an interesting motor ( -- big advantage there is the ball bearings which cut the no-load current substantially (0.7A vs. 3.8A for the Andymark); it is a 19k-RPM motor though. The winding is likely fairly similar.

One thing I did on the estimation/calcs I gave to you is I used 0.1 ohms for the wiring resistance. There's no "right answer" for that but I've found that the batteries droop quite a bit more than the manufacturer claims (via their "internal resistance". It's not linear with load, and larger batteries perform quite a bit better, so with the 20Ah ones you have 0.1ohm may be too large. It makes a big difference in the starting torque but not as much on the overall speed, though this depends on the motors. The AndyMark and Vex motors will pull a *lot* of current at startup at 18V, and I think they will burn out the switches very quickly. Using a good ESC would get rid of that problem.

If I put in 0.05ohm I get the same numbers you did with that motor; if I use the 0.1ohm (to compare against the ones I posted), I get 80Nm of peak torque and 11.7mph no-drag (note that I had posted no-drag #s; probably too late at night :lol: ). The huge drop in startup torque is simply due to the fact that the Andymark wants a lot of current (400A stall for two motors @ 18V vs. 200A with stock motors in that configuration) and the battery/wiring really can't supply it. Cold-Cranking-Amp measurements (common ratings for "cars") are typically measured at 7.2V, so that's a 5V drop, and for a high-quality small battery these are typically ~100A (see, so that is 0.05ohm. On a 20Ah standard SLA it's probably more like 150-175A (Odyssey rates their 15Ah extreme battery at 200CCA).

Switch and gearbox destruction were my main concern when I posted wrote that caution about the Banebots 18V; it's 33% more current (for the same voltage) as stock and at 18V it's 2x the current of a "stock 12V" setup. . The AndyMark one is double the stock one at 12V and at 18V it's 3x the stock 12V setup. That should fry switches pretty quickly :). If you combine a hefty battery with a high-stall-torque motor, you can also blow out gearboxes pretty easily. An ESC helps a lot; even a high-current one help substantially, because you don't go from 0->18V in 1mS like you do with a switch -- it takes longer than that for the kid to push the throttle down all the way, and the first few mS allows the motor and gearbox to take up all the lash in the tooth-to-tooth spacing and you don't get a hard impact).

The 'Peak torque at takeoff' in the spreadsheet is a measurement at the tire of the vehicle and is a combination of 3 factors: Net current (after wiring losses) * motor torque * gearing ratio. If you're asking about the "Motor Torque Constant" row in the spreadsheet, that's just the stall torque (700mN*m) / stall current (130A) = ~5.4mNm per Amp. As expected, the 21k RPM Andymark motor will produce less torque per amp than the stock motor or a 7013F or a Banebots (14T) motor, because magentic force generated by current in a wire is roughly proportional to the # of turns, and the no-load speed is roughly inversely proportional to the # of turns. Because a low-turn motor can also "consume" more current, the stall torque doesn't always reduce but the maximum amount of thoeretical power goes up with a lower-turn motor since you have about the same torque -- with more current -- but at a higher RPM (the 'work' the motor can do is proportional to torque * radial speed).

Thanks for finding that post about the bit -- I'll edit my previous one to help avoid confusion! My new place has a mill (an old Bridgeport J-head) and I've still got my drill press, so maybe in about a year after I get everything unpacked I'll have to do a run of Quad Damage-mod gearbox plates or something. I've been really happy with the performance if the 2 vehicles that I have in the fleet that have them.

Keep me posted on how the 19T 7013F (or whatever you decide on) conversion goes!
Awesome Hammer I appreciate it.

I have ordered the gearboxes, pinions, some LED headlights, switches, etc and the 9013 motors so I have a small project to get done. Ill update progress when complete for sure.

I guess Im trying to Find where the Calculations are found on the spreadsheet for starting Torque. For Example an earlier post you had:
Nichbio 7013F and a 19T gearbox at 18V: 8.5mph and starting torque of 100Nm.
Nichbio 7013F and a 22T gearbox at 18V: 9.9mph and starting torque of 87Nm.
Banebots 18 V and a 22T gearbox at 18V: 9.0mph and starting torque of 93Nm.

Where does the 100,87, and 93 come from? I looked at the spreadsheet and am trying to find similar numbers to round up/down to but Im not seeing those calculations when plugging in the same numbers. I googled up some formulas but also did not come up correctly

I decided I will use the Original Gearbox and attempt the Quad Damage first gear delete MOD. I feel I can chop one up in an attempt to see If I can get the pinions to match the second gear. Looks fun and challenging. I see in your Quad Post you have the motors attached to the Aluminum Sheet in a sleeve type holder. Was that custom made or an off the shelf component?

At that point Ill have to get into an ESC since running 24v.

Again Thanks for the insight
Ah, my bad. In my current rev I have some "as-fit" measurements for the 7013F and Banebots motors -- based on speed and rough torque measurements, and I had plugged those in. The 7013F in the older spreadsheet that is online is from the manufacturer's specs, but my measurements (on 3 motors) all showed that the stall current is quite a bit higher than spec'd, as is the stall torque (torque per Amp is slightly lower than spec). They're also about 5% slower than spec.

That makes them very similar to the Banebot 18V (Mabuchi 8514) motors in terms of RPM & torque capability -- slightly faster, slightly lower torque, but also 1/6 the cost.

If I find a few mins tonight I'll try to update the link with the newer version. I do want to get more accurate measurements on these some time (with a more elaborate and precise measurement setup).
A quick update on the Jeep Mods.

I installed the Nichibo KC3SFN-8021F using the stock gearboxes and 16T Pinions and the jeep is clocked at 9.6mph in high gear at 18v (using a GPS Phone APP). I did also install ML Toys Break Mod to help the slowing down as more of a slight roll than the locked wheels skidding. So Far have not had any issues (apart from Tripping the Fuse breaker 40A) but running these at 18v I dont think will last long but it sure does move. I also make sure my son takes off in first gear before moving the throttle as the initial take off is too much on the Electrical System since I tend to trip the breaker when that happens

I still have to mod the new 19T gearboxes and mount the 9013f motors hopefully ill get to early next week and ill report back
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