Pinion & Spur Gears for SCX 10

[garyedson]

Hi -- My first post. I just bought an Axial SCX 10 and have run it around the wooded back yard. Runs great! Lots of fun! But too fast, since I also intend to use it for a couple of grand children, 5 and 7 years old. I think a top speed about half of stock would be about right.

Instruction Manual by Axial has great line drawings but not much actual information. Towards the back there is a Gear Ratio chart which I find confusing. Are the pinion numbers, 10-35, and spur numbers, 70-96, the number of teeth? What significance does "48 pitch" at the top have? Seems to me that spurs and pinions go together as pairs because the shaft center lines are constant. Yet the chart does not seem to list these gears as pairs.

Likely there is an explanation of all this in one of the forums, but I have not found it. Can someone explain to me or tell me where to look?

Finally, to cut to the chase, where should I go to buy gears for the SCX10 and what whould I order to cut top speed to about half?

Thanks for your help. Regards. -Gary

 

[Solitaire]

Welcome to the forums. Your choice of an Axial rig is a good one. A very solid platform with a ton of aftermarket parts available most anywhere.
Your SCX10 should have come with a 20T pinion and an 87T spur gear. I'm not sure you or your grandkids would be real happy with half speed. I might suggest just changing out the pinion to a 12 or 13T and see if that fits your comfort level. If you would like to keep the spur cover (if it has one), you're pretty well limited to the 87T. I'm not sure anything larger would fit under the cover.

Yes the listing for spur/pinions in the manual is a tooth count and the 48 pitch is standard on the SCX10 and many other RC vehicles. Some buy 32 pitch (coarser teeth) spur and pinion for extra strength, but I don't think it's necessary for a trail rig. 48P is a lot quieter as well. You should be able to find 48P pinions at most hobby stores and certainly the online ones that deal in RC cars/trucks. As a side note, you'll need a pinion to fit a .125" motor shaft.

Good luck with your new truck and if there are further questions, please ask away.

 

[Trubble]

Are the pinion numbers, 10-35, and spur numbers, 70-96, the number of teeth?

Yes.

What significance does "48 pitch" at the top have?

48 teeth per inch at the datum circle. Look at any ruler graduated in 1/32nds and 1/64ths. Imagine those graduations are gear teeth. They'd be wildly different in size and wouldn't fit together. So, if you only change out one gear, make sure you get a 48 pitch to match what you have. If you want to change pitch, then you'd need to replace both gears.
Replacing the motor with one that has a higher 'turn' count will also slow it down. But I'd try a re-gear first.

Seems to me that spurs and pinions go together as pairs because the shaft center lines are constant. Yet the chart does not seem to list these gears as pairs.

Negative. On either side of the pinion there should be two screws going through slots and into the motor. Loosen the screws, and you should be able to slide the motor towards the spur to take up slack for your smaller pinion, or slide the motor away from the spur to make room for a larger spur.
When setting how tight they mesh, I usually hold the pinion and rock the spur back & forth, making sure there's a small 'tick' of movement. Too tight causes a host of problems (overheating, battery and/or ESC issues, etc.) and way too loose can lead to gear teeth getting rounded off or knocked out.

Likely there is an explanation of all this in one of the forums, but I have not found it. Can someone explain to me or tell me where to look?

Scroll up, there should be a white box in the upper right hand area that'll allow you to search for what you're looking for. Also in the upper right hand area, just below where it says "Welcome (screen name)" there's the word 'search' with a down-arrow, you can try that one too. And a little farther down, just below where it'd tell you how many pages are in the forum you're looking at, will also be a box marked 'Search this forum', again with a down arrow. This is helpful if you're in a specific forum and don't care to search the entire boards for an answer.

Finally, to cut to the chase, where should I go to buy gears for the SCX10 and what whould I order to cut top speed to about half?

Either your local hobby shop or find yourself a favorite online retailer (Tower, A-main, TCS, RCP, RPP, Stormer, are a few places to begin one's search). There should be a 'Vendors' forum out in the main forums screen, you can pop in there and get more names to search for info on, too. Quite often if I'm on a hunt for something, by the time I have to give up, I'll have a dozen tabs open.
As far as what to buy, the stock Axial gears have done me fine, I've seen no reason to change them out. So I'd look for Axial parts or Robinson Racing also has gears available for these things (look in their AX10 Scorpion section).

Thanks for your help. Regards. -Gary

If your truck's running an AE-2 speed control, there should also be a top speed adjustment in there that can be accessed with a CastleLink and a computer. I forget what exactly it's called..... "Max. Power" maybe, expressed in %. But if you're running around in grass, mud, sand, wooded areas, etc... I still think you'd do yourself well to lower the gearing. If you like the top speed and want to maybe keep that for days you're running without the grandkids, then the ESC adjustment and stock gears would allow you to go back to 'adult speed' fairly quick and easy.

 

[Jus]

Easiest thing you could possibly do depending on the radio you're using is dial back the Throttle % or EPA to under 125 or 100 or whatever the setting may be. Then in an instant you can return it to full power for yourself or what not without changing gears.