hot rod mower in the making

I have an Excel-based sheet I do all my calcs with. Reverse calcs and actual speed and RPM measurements reveal it to be dead-on accurate. Give me a chance to bounce some numbers off yours, and we'll go from there. Thank you.

Most excellent, thank you sir...

If you google, you can find online calculators to figure speed/rpm. But, you need the ratio for every gear, belt ratio's, tire circumference, and engine RPM.

I used one for figuring the speeds on our mowers.

Yeah. I kind of like to re-invent the wheel and build better mousetraps that suit my particular mouse. I'm funny like that. 

You're not gonna hear ME argue that one! I think I'm becoming famous for it! LOL
-Actually, as far as a speed calc goes, that's exactly what I did- I lifted an existing one off the net and reconfigured it to suit my own needs at the time.

So far I have only found some generic cross reference charts which seemed pretty useless to me. Luckily I have plenty of experience writing spreadsheets so I just sat down and figured it out.

I appreciate the cross check as all this gearing business is new to me and although it seems fairly straightforward I want to know that I'm not off base. Particularly with my logic on the jackshaft input and output.

Im really digging the lowered look. i like how you stuffed the tires up in the fender, not just flared the fender. Looks fast just sitting there. Paint ideas?

I actually widened the fenders 6" to come out and cover the tires. I am loving the square body of this rig. I can't wait to get it done.

Paint - man I am not artistically creative at all. I will probably get some pics into photoshop and do some color overlays and see what strikes me. I will be painting it myself - base/clear.

I do have a friend who does amazing airbrush work I will probably have him throw something interesting on top of my base before I clear.

get a mossy oak wrap.. lol

noooooooooooooooooooooooooooooooooooooooo.... 

I am wondering if I can get lower profile tires for the stock front wheels. Any direction on that?


I am thinking about trying to mount a brake rotor and caliper to the jackshaft itself for brake power since braking at the actual axle doesn't look real do-able. Any thoughts on this?

zninja wrote:

I am wondering if I can get lower profile tires for the stock front wheels. Any direction on that?


I am thinking about trying to mount a brake rotor and caliper to the jackshaft itself for brake power since braking at the actual axle doesn't look real do-able. Any thoughts on this?

You may be able to find some tires off bmi karts. The brake set up shouldn't be to hard to figure out, i'd take a 3/4in hub from tractor supply and put it on the axle, then weld a brake disk to the hub and go from there. I'm not sure about the room you have but i've seen it done before.

The problem with braking the jackshaft is this: from your jackshaft to your transaxle, you have a belt. If you lose the belt, you lose the brakes. Not too safe, imo.

Instead, consider attaching a brake rotor to the transaxle input pulley.

Regarding the front tires, many race machines including mine use 13x6.50-6 on the front. Many use go kart rims, but they will also fit on factory rims if you prefer.

That's good and there many actually be enough room back there to mount a rotor. I like it. Thanks.

It is a very workable solution. When I get the chance (might be spring though) that's exactly what I'm doing to MULE. I do not have enough clearance on the axle to install a big disk brake, and I definitely need to upgrade the brakes.

Are you looking at attaching to the pulley itself? Or to the shaft? I guess you could just weld the rotor to the pulley huh?

Doc Sprocket wrote:

Regarding the front tires, many race machines including mine use 13x6.50-6 on the front. Many use go kart rims, but they will also fit on factory rims if you prefer.

What would be the best tire for going fast and turning left? Slick, turf or straight ribbed?

Seems to me like the straight ribbed might be best...?

get something like what fearless has on his racer.. ribbed arent meant for speed. turfs cant withstand the forces generated of a racer/hot rod. something like kart tires, but not slicks... if there is any sand or anything like that on your riding surface youre done.. atleast you might be able to save it with treads

I've seen true racers run mini sprint tires.

Besides the belt, braking on the input side of the transaxle has the additional problem of being tied to the gear. If you are in neutral you have zero brakes, ditto if you completely shear shift keys or have other transaxle failure.

I don't know how to brake this thing any other way without spending a bunch of money which I don't want to do. The trans brake may have flaws but I think it is my best economical bet.

Are you still running the stock transaxle.

One cam always leave the factory brake in place as an emergency brake in case of any failure, and even double as a parking brake.

To do mine, I had simply planned to mock up the trans pulley and the rotor on a dummy shaft to hold them concentric, then zap together. Planning ahead is key though- if you're going to change pulleys any time soon, do it first.

Good turf tires are used very commonly in tractor racing. The favourite choice seems to be Carlisle Turf Masters. The tires that are best for you will depend on the surfaces you will be running on, and the class you are building for, if any.

With that said, many sanctioning bodies mandate that the service brake be mounted directly on the axle- due to the potential safety issue associated with braking the input or jackshaft. My racer uses an axle-mounted brake to comply with said rules.

Speedfreek241 wrote:

Are you still running the stock transaxle.

Yep.

Doc Sprocket wrote:

One cam always leave the factory brake in place as an emergency brake in case of any failure, and even double as a parking brake.

To do mine, I had simply planned to mock up the trans pulley and the rotor on a dummy shaft to hold them concentric, then zap together.  Planning ahead is key though- if you're going to change pulleys any time soon, do it first.

Good turf tires are used very commonly in tractor racing. The favourite choice seems to be Carlisle Turf Masters. The tires that are best for you will depend on the surfaces you will be running on, and the class you are building for, if any.

With that said, many sanctioning bodies mandate that the service brake be mounted directly on the axle- due to the potential safety issue associated with braking the input or jackshaft. My racer uses an axle-mounted brake to comply with said rules.

I'm not racing for real. Once a year at the redneck Olympics, no rules.

The track starts out as grass in the morning, is torn up by 4 wheelers racing and then the mowers run. So its pretty rough.

Then I'd call slicks a bad idea...