M.L. Toys
M.L. Toys
HobbyMasters M.L. Toys
Need new motors? Grind a gearbox? Adding teeth to a pinion?
Where can we get ~0.4-0.5” Wide Face Width 13 tooth 32 pitch pinions with 5mm ID shaft?

Are these avalible anywhere in a wider format?

Press fit?
Maybe even a recessed set screw. At that diameter and shaft size, it does not leave a lot of room for a set screw.

I was told that the pinion I have “may not be a 32 pitch” but measuring the unit I have out is seems to be exactly a 32 pitch unit?

Can someone clarify this factor please?

The pinion I have is a 13 tooth with pitch diameter of ~0.405”

I would like to find one with a width ~0.5”, as all the readily avalible hobby units I have seen are ~0.2” wide. While that in itself is not bad considering the mating gear, there is so much axial play in the mating gear sets, that it seems to require a large width pinion like they come with IMO to cope with all that slop.

Is the lack of chatter here based on my searching any indication of availability of these parts?

If this is still about your other topic (replacement parts for the Hurricane): The 13T that is used on the Hurricanes is not a standard 32dp pinion and you will not be able to find a replacement. You need a 14T pinion.

To answer your question, Hot Racing sells a suite of "long" pinions that probably fit your needs. This is the 13T version; the part #s are just "NSG2**L" where ** is the # of teeth, so 13T is a NSG213L like this one: ... 2581406732

There isn't much slop in the FP gearboxes and the stock 1st gear is only 4mm wide. Are you building a custom gear set?
Can you explain “not a standard 32dp pinion” in more detail please?

Specifically about the diametral pitch, tooth count of the pinions used, VS a off the shelf 32 pitch.

Do they use a slightly deeper root? Perhaps clearanced to keep the same motor spacing on a range of 3 pinions per gearbox, Is this the issue that you are implying?

The issue doesn't seem very clearly outlined. is the above understanding close?
Good background material is in the 7R Gearboxes and Pinion Research Thread, but here are some hard #s and pictures.

First, disclaimer: What I am writing here only applies to #7R gearboxes. I recently got an old Hurricane with an original #7 gearbox and the 13T pinion there is a standard 32DP pinion, with an outside diameter of about 0.475". The 7R 13T pinions in my newer Hurricane measure at 0.505" -- or in other words, they're about 1 tooth "larger". Typical OD quoted is 1/(diametrical pitch) * (# teeth +2), eg. 1/32 * (13 +2) for a 13T, 32DP gear = 15/32" or 0.469" outside diameter. The 7R 13T pinion is the same OD as a 14T 32DP standard pinion.

I'm assuming the 0.405" you listed was a typo or you're measuring at the root of the teeth rather than the OD. Can you clarify?

Fisher-Price does this on other sizes: the 15/16/17T gearboxes have 3 interchangeable pinion options. The difference is most noticeable if you have all 3 next to each other. The 15T gear has taller (pointed) teeth, the 17T has them shaved off, and the 16T is "normal". They all have the same OD.

Since you want to buy new pinions, you're unlikely to find them in wierd sizes like this, so you need to determine the right size to fit in your application.

Note that Fisher-Price isn't the only manufacturer to do this. Vex Robotics, for instance, sells interchangeable 11T/12T/13T pinions for their CIM motors, which are listed as drop-in replacements for trading off speed vs. torque without having to change any other gearbox components.

Here are a few measurements I took of motors/gears I had in the garage. Note that the "industry standard" 32DP gears I have could be deemed slightly undersized (by 0.010" or so). In my applications I'm usually setting the gear interference manually so this isn't really a concern.

That REALLY helps clear up what you are talking about, thank you for taking the time to post a photo!

Would it be alright to either post that to that 7R GEARBOXES AND PINION RESEARCH thread. Or allow me to, because that cleared up all the confusion I had on the matter.

I believe I have the #7 boxes, and I think this is where the confusion is coming into play.

To measure my pitch diameter, I simply measured from the root of one side to the tip of the opposing tooth.

This should give a fairly realistic number for pitch diameter, and seems to validate my belief that the pinion I have is a “true” 32 pitch unit?

My pinion looks virtually identical to your photos bottom left “Original #7 gearbox Hurricane 13T” as well as measures out to the same spec ~0.480”

You mentioned that “Hot Racing” sells a wide 5mm ID pinion.

Am I to assume that the top left is a “Hot Racing” 13T unit with a 5mm ID?

How wide is the tooth face width on those particular units?

I notice the diameter of the two 13T pinions seem do differ?

I assume this is only a manufacturing tolerance, probably a less sharp top land of the tooth?
This is the best 32p 13T pinion with 5mm ID I have been able to find that matches my desire for a "more stock like" wide face width. (do you guys typically shim those gear sets, they seem pretty susceptible to wandering inside the box, and not fully interfacing with the mating gear particularly here with no way to control deflection from misalignment of the motor axis)

Any other options that might be more suitable? A full face cut would be desirable. ... Sw5JJZjy4J


I am also thinking about cutting the stock units to size, but really prefer to just get one off the shelf... as I dont seem to be able to procure a backup set should I need to...
Yeah, everything you are saying aligns with your gearbox (and pinion)being a "7", not 7R. If you have the clips around the edges and the thin-wall final gear then that's definitely a "7".

In that case, yes -- you want a standard 32DP 13T pinion. The two 'industry' pinions I pictured are cheapie "GoolRC" ones from ebay (eg. this set). The measurement difference I showed is, I believe, mostly an artifact of the tooth shape. I bought 4 sets to do quad-damage gearboxes and haven't had any issues with them, and I am also using two of the 15T ones in a "normal" 7R 15-16-17T gearbox, with a modified centering sleeve (offset-drilled, since normally you'd want a 16T gear for that). Even in that application I was able to dial the engagement amount I wanted, but I believe they would work fine as a standard replacement, WITH the appropriate plastic centering sleeve. I would not recommend running a 775 motor in these gearboxes without a centering sleeve (you can use 1/2" PVC and drill it out; the OD is the same as the factory sleeve)

have some 17T ones from Hobbystar and they look identical to the GoolRC ones; should be a solid choice. These are about the best I've seen in the standard length. They have about 7-8mm of usable gear length, which is among the best I've seen aside from the the Hot Racing "long" series, which I haven't personally used. Some of the brands have only a 4-5mm usable tooth (Associated Racing), so stay away from those. The Hot Racing standard ones are 6-6.5mm.

I haven't tried redrilling a stock one but am ordering the parts to try it. I have a LOT of stock gears around and it would save me some good money.

Rereading your original post I see you were concerned about shimming the gear sets/wandering. If you're referring to how to hold the motor in the box relative to its gear, then that's the centering sleeve I mentioned up above. The factor motors have them installed and I think it's important to make one for the replacement/775 motor as well, though not everyone agrees. See this topic for more information about my low-cost solution (though low-cost only if you have the right drill bit ): viewtopic.php?f=9&t=21263&sid=0f10a1ae3 ... 6f#p146948

Hopefully this helps!
Thank you for being so helpful!

In regards to the shimming, it's the axial play I am worried about. The gears I have are about as loose inside of the box as can be, I would estimate ~1/8"-3/16" of axial play, not to mention the easy deflection of the mating spur to the pinion.

Do people shim the gears to reduce the amount of axial play? Or is that even a reasonable expectation based on the hardware and case being so flexible?

I have another pressing question, if you might have a idea or opinion on.

Are these 550, and specifically 775 motors 0° timing ? They don't appear to be truely mechanically or dimensionally 0° timmed?

And if so, is there any reason to worry about that factor at all?

There is no direct coupling between the two opposed boxes...but I assume the ~+5° of timing they appear to have is now doubled when you rotate the opposing motor in reverse -10°?

It was the reason I purchased those 550 Titan motors, as this factor is actually mechanically accounted for in their construction. They just don't stand up to our abuse though.

I suppose if there are no counter rotation 775 options, it's a moot point...
Hmm.. That much axial play doesn't sound right. The #7 gears have a different center cut in the gear (it's a hexagon hole riding on a circular shaft), and because of the reduced contact area I would expect them to wear quite a bit faster than the #7R gears (circular hole with a circular shaft). The #7 gearbox I have does have more play than I see in any of the 7R ones that I have. Additionally, the #7 pinion shafts are larger, so the linear speed at the metal:plastic interface is higher for the same RPM, which will accelerate wear further (the #7Rs really are much better engineered).

With that much play I would definitely be worried about marginal tooth engagement. How does the 1st gear look -- is it starting to get the ends shaved or any other signs of wear?

Given the relative cost I would probably run them until they broke and look for a deal on a set of 7Rs to drop in. Replacing individual gears is more expensive and it's not clear to me whether there are good options for shimming (did you have anything specific in mind?). I suppose if you could find a very thinwall teflon or polyethylene tube of the right diameter maybe it could be inserted.

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