Cog problem

shane0312

I have a hotbodies nitro car and the gear cog (the bigger of the two) isnt engaging properly with the drive shaft and is shearing the cog until it just doesnt engage anymore.

This is my third cog that ive gone through, does anyone have any idea why this is happening and/or any solutions?

techguy

I had a car once and had the same prob I think..
Either a stone got into it and ground down the teeth or else the engine is not mounted securely to the chassis,by this I mean the crankshaft can probably turn about 2-3mm either way. In my experience this is enoguh to only have engage the gears and shear them..
I could be way off the mark with your problem...but you could check these things out.

Hakko

Devion

Also the gears could be too close or too far apart from each other.
The simpliest way to guage is get a strip of a4 and fold it in half then put the to gears together

now when the paper goes through the gears it should become wavy not teared and shouldnt be loose.

coolwings

shane0312 wrote:

I have a hotbodies nitro car and the gear cog (the bigger of the two) isnt engaging properly with the drive shaft and is shearing the cog until it just doesnt engage anymore.

You are
A not retightening the engine mountin bolts, (under the car), thereby allowing the vibration to loosen them, the engine shift, and the play in the gears shears a tooth, and later on, more teeth, when power is applied to accellerate.
or
B running in a gritty gravelly area, where all teeth will get sanded down more or less equally, until the spur gear needs replacement

shane0312 wrote:

This is my third cog that ive gone through, does anyone have any idea why this is happening and/or any solutions?

A spur gear should last for one to three gallons of fuel, if looked after correctly, and barring accident from crash damage. It is a consumable however and has a limited life.

shane0312

coolwings wrote:

A spur gear should last for one to three gallons of fuel, if looked after correctly, and barring accident from crash damage. It is a consumable however and has a limited life.

Yeah the problem is I've only run less than a litre of fuel through the engine!

coolwings

shane0312 wrote:

... the problem is I've only run less than a litre of fuel through the engine!

If you have finished off three spur gears on a litre then either the engine is coming loose regularly, or the wrong gear is fitted giving a mis-match of gears (this would be very unlikely, unless parts from another make had been incorrectly fitted into your car).
Try a test ... hold the cylinder head from above the car...can you twist the engine so the gears mesh, and then separate? Can you separate the gears from each other by pulling on the end of the engine drive shaft where the gear is fitted?
Either way, the engine should not part company with the spur gear.

BTW I'll bet there is no treadlock on the treads of the engine mounting bolts, (underneath the engine). If that is the case, try some on those 4 bolts, it helps prolong tightness in this critical area.

Devion

May i suggest you use the blue loctite not the red lol.

no leaf clover

shane0312 wrote:

I have a hotbodies nitro car and the gear cog (the bigger of the two) isnt engaging properly with the drive shaft and is shearing the cog until it just doesnt engage anymore.

This is my third cog that ive gone through, does anyone have any idea why this is happening and/or any solutions?

the fact that it's a hot bodies i doubt this but if u drive on grass it damages them. found out the hard way like you!!