DIY Pedal Tractor Gearing

I am making my Son a DIY Pedal Tractor and I am trying to get the gearing set up. I was planning on using a bicycle crankset with a small sprocket and for the rear axle I want to use a steel rod (maybe 3/4 inch diameter). The dilemma is finding a bicycle gear to install on that steel rod. I need to find a gear that will fit a 3/4 inch diameter steel rod. The problem is that I'm not sure where to find a gear that has something attached to it that can clamp (or something) onto the axle.

Any idea how or where I can find a gear?

 

Mcmaster Carr has everything/

https://www.mcmaster.com/sprockets

 

Look at go cart parts. All require that the shaft have a keyway and most fit shafts 1" and larger though there are a few 20mm (.78"). They are usually sold as a hub and then you pick the size sprocket you want and bolt it to the hub.

 

Thanks Guys. Pilot Done- I looked at the Go Kart option but the back wheels I have take a 5/8 inch axle and are not keyed. So I found some axle rod online and Home Depot but my issue is still how to affix the axle to the wheel and the wheel is free spinning so I'll have to maybe weld that to the shaft or something.... Any other ideas would be great!

Thanks

 

Just as a side note, because your only talking about the rear sprocket, remember to get a rear sprocket to match the teeth on the front sprocket. The links on the drive chain will be spaced at a certain spacing, so the sprockets will need to be the same tooth spacing etc. If not, the chain will keep jumping off the sprocket.

 

You can NOT use free spinning wheels that have bearings in the hub. Your rear drive wheels need to be rigidly attached to the axle. You need to pick your axle, rims/tires, bearings and drive sprocket all together as a system.

Normally you use a rim that fits over the end of the axle or you have a hub attached to the axle that the rim bolts to. Welding is not the best option as it will put a lot of stress into the metal in an area already under high stress. It might be OK for a small child's pedal cart but it's iffy, especially with a small axle size like 5/8".

 

Pilot Dane- I tried attaching the wheels to the axle using cotter pins. The wheels are dolly wheels, the axle is 5/8 inch steel, the cotter pins are 1/8 inch. I drilled approx 1/8 inch holes through the rim of the wheel and the axle. But the first time he tried riding it, the cotter pins snapped. Would a 1/8” bolt work better? Here’s a couple pics.

 

A bolt or solid pin would be stronger than a cotter pin.

Did you give up on the pedals/gear?

 

If anything use a piece of 1/8" solid rod or even the shank/smooth end of a drill bit.

 

No, I did not give up on the gearing. I bolted the gear to a gas pipe flange then put it onto the axle and drilled through the flange and through the axle. I put a cotter pin through that bot I'll probably have to up that to a bolt. You can see in the pictures...

 

 

I’m at a loss here. I originally used cotter pins, they sheared off so I tried hitch pins and they sheared off too. My latest attempt was using stainless steel bolts. The bolts were #6-32 stainless steel and they sheared off also. What the heck can I try??? It’s so frustrating to do all that work and one of the simplest steps is a huge hurdle!

Thanks for any help!

 

Try some shear pins for a bush hog

 

need to probably increase the thickness would drill a larger hole then can probably get by with a bolt or pin that is thicker in size

 

The more I read, I see that Clevis Pins and Shear Pins have really good shear strength but finding them in 3/16 inch diameter x 2 inch length is tough. If I used 1/4 inch diameter, is that too large of a hole in the axle? The axle is 5/8 inch in diameter.

 

Bolts are really weak. Look closely at it and you'll see that your 6-32 has a good portion of it's diameter cut away by the threads. Then the sharp base of the threads is perfect for starting a stress fracture and the bolt breaks.

Use the shank from a drill bit. You can order steel, hardened steel and stainless rod from Ebay for really cheap.

 

probably dont have much choice other than drilling it to 1/4 inch if your going to try to make it work, you can buy longer bolts with a shoulder ,1/4 inch clevis or wire lock pins are common in 1/4 also. plenty of rear tine tillers with the drive wheels held on with a 1/4 inch bolt or clevis pin but their axle is larger than 5/8 though.
you probably dont want to weld the wheels on but thats always an option with a steel wheel also.

 

I still think that a roll pin would do the job, from the standpoint of strength, as well as the fact that, with a proper size hole, the fit would be snug, no slop like you have with a cotter pin or bolt, hence minimizing the sheering effect between the axle and wheel. Also, I said pin, not pins, because, with no differential, I think that you want to pin only one side and use a locking collar to hold the wheel on the other side. Otherwise it will do fine straight ahead but the wheels, hence the pins, will fight each other when turning.