So I'm building a yard kart for the kids from a pair of old John Deere lawnmowers ala the article that GRM reposted. Here's the build thread:
https://grassrootsmotorsports.com/forum/build-projects-and-project-cars/maniacs-john-dyr-yard-cart-summer-project-with-the-spawn/174023/page1/
I have one of the peerless limited slip diffs on the axles and I love the idea of having a diff on the kart to make it easier to drive but still be able to slide around. I know most go karts have a solid axle and a single disk brake attached to it. Can I do that with the diff? Will braking one side do weird things or will it all just kind of work. The lawn mower originally had a kind of hoop that clamped down on the diff I would love to use that but I don't think I'll get the braking power I need out of it.
Any thoughts on using the original braking system? If I get a caliper and rotor where can or should I put that in relation to the axle and diff? Do I have to have two calipers and rotors one for each side? If I can't use the original system I was gonna look for a scooter or moped in the junk yard and adapt the front braking setup unless someone knows a cheaper alternative. A lot of the go kart dedicated stuff is ridiculously expensive.
Could you attach a disc to the diff? Like drill and tap the gear for some stand off spacers and use a motorcycle blank.
In reply to Appleseed :
Maybe. I don't really know how important all parts of the diff are exactly so I'm not sure where I can go drilling in willy nilly. If I can't use the clamp brake thing and if I have to attach to the diff rather than the axle that was my plan. I'm kind of hoping I don't have to because getting that lined up exactly true isn't always easy with just home tools and I don't have spares if I wreck it.
I would at least try the factory brakes. Get a new band if it needs it and adjust it properly, then decide if it's good enough. Our yard kart has pretty crappy brakes and they've always been good enough.
Is the picture above of the differential you're using?
If so, then that portion on the backside of the sprocket is for an external drum brake (a leather or rubber strap that is tightened against the drum).
You could also add a rotor to the opposite side of the differential using the bolts already there that holds the case together. Just be careful when installing it, but its a relatively simple device.
I mean you could possibly even use the sprocket itself as the brake rotor, just fit the caliper into the space where the chain doesn't run. Done.
It does make the sprocket a faster wearing item, so make sure you can get or make replacements.
Wonderful thank you. I took a closer look and Stefan is right the drum is a seperate piece and I could remove it and use its mounting for a rotor. For the original brakes I'm glad that gearhead mentioned they work well enough in his kart. I was afraid that bringing the top speed from about 8mph to 30mph would overwhelm them even with the lower weight. I looked at the band and it seems quite worn but seems to be lined with what appears to be normal brake pad material. I wonder how expensive a replacement band is. I do like the idea of the brakes not being overly sensitive so the kids aren't constantly locking up the rear every time they breathe on the brake pedal.
Thank you for the info it was super useful and I have a good plan with a couple branching options now.
Ive see setups where the sprocket had a caliper mounted in the void between the top and bottom part of the chain and the sprocket was the disc.
If you can re-use the factory band brake, it will provide plenty of stopping power. I wrote the 10-year-old story on Yard Karts that keeps popping up and we built several karts with that exact setup and it worked very well, even at speeds pushing 30mph. I never found a cost-effective source for new replacements, but they can be re-lined with brake drum material (antique car suppliers sell it) and glue.
That's the good news. The not-so-good news is that you probably don't have a limited slip diff, you more likely have an open diff. If one wheel is lifted (like the inside wheel on a hard turn), when you apply the brake, it won't stop very effectively because it will mainly be spinning the lifted wheel backward. If you take your diff apart and it looks like this inside with spider gears etc., it's open:
Some of the low-end mowers have a puck-style differential instead of a gear type as above. The puck-style diffs can act like a limited slip if you can find one. John Deere's and other name brands usually have the gear style. I've seen the puck-styles in Sears and other lesser brands. Basically, there is a disc connected to one axle and some spring loaded pucks that connect to the other axle via friction. Some are open on the sides like the picture, others have the pucks and disc inside a similar case to the case on your diff. They usually work pretty well out of the box, but you could tune one by changing to stronger/weaker springs if you really geeked out. Anyway, here's the best picture I could find (couldn't find an exploded view):
So maybe I've confused you or depressed you because you don't have a limited slip. We've run your style and just done our best to keep from lifting the inside wheel by either limiting speed or putting sway bars on the front. We used the factory center pivot axles (lowered) with no springs, but home-made sway bars really help handling. We'd make the sway bars out of 1/4" to 7/16" solid rod and find the one that offered the best handling compromise.
We've also put really heavy grease into the open diffs and found that it tightened them up a lot to nearly a limited slip.
Good luck!
In reply to Carl Heideman :
This is great info and that article was the one I reference in my build thread as the inspiration so thank you so much for writing that. It does look like I have an open diff. I'll try the heavy grease method, ultimately just having a diff will be nice for the kids to be able to steer easier so I'm not worried. I expect if it comes down to it I can just weld it up as well.
For the brake band I found some high strength brake and clutch lining material. I ordered 2 feet of it for $10 on McMaster Carr so that is a great bit cheaper than I expected to have to spend to get the brakes ready again thank you for the info.
Sounds like you're making great progress. I see you're keeping the kids hands-on, too. It took me a lot of patience, but I had mine do 90% of the work, including all of the welding. I just wanted to get in there and do it for them, but it paid off huge over time for them as they picked up a lot of skills. And of course, sloppy work (which also took a lot of patience to watch happen) resulted in breakdowns, which taught them to be thorough and not do sloppy work. They don't like Roadkill because of it.
Many hundreds of karts and mini bike the caliper grip on the sprocket.
