Load of questions

[frdtrkrul]

New guy around here and been been browsing for a few answers but can't quite seem to find them.

I'm in the process of gathering parts to build a garden tractor for my dad in the style of a go kart per say. Going to use a Briggs and Stratton 305cc with 12 volt electric start. Obviously not going for speed but instead a good amount of torque. I'm leaning towards using a torque converter with a jackshaft. Both rear wheels will be powered. Both rear wheels will have individual brakes as well for sharp turns.

Not using a gas pedal but instead a throttle more or less how the old tractors were.

What I need to know is what gear ratio to use for torque. Not sure what gearing to use. Also whether to use belt or chain. Chain will more than likely break more parts and where as a belt will slip. For brakes I'm guessing disc will be best compared to the belt style. Sounds like to do the individual brakes in the way I am describing I'll need to do a fixed axle. Going to use modified 5 lug trailer spindles with a welded on gear or pulley (depending which style I go with).

Also not sure on what I can do for a reverse. For what we'll be doing with it, reverse is needed (no necessary) but it'll be easier to back up to move a trailer around. The trailer in question is one for a 1974 Strarcraft 17' boat, weighs around with everything close to 1,600lbs. Seems like a lot of weight but we've moved it before with a lawn tractor (until I blew the connecting rod).

Sorry if I am beating the horse to death here on the gear ratios, seems like more people go for top speed rather than torque.

Thanks in advance for the help!

Other option I am thinking of is run separate axles to the rear wheels.

 

[firemanjim]

To have twin brakes on the rear, you must use a differential. If you gotta have reverse, look into using a diff from a lawn tractor. 3spd plus reverse..... For ratios, we need to know more. Tire size is most important... BUT for basic knowledge, the bigger the rear sprocket, the slower/more torque you will get.... Opposite on the engine sprocket....

 

[frdtrkrul]

I have an old 3 speed plus reverse transmission but its only for a vertical shaft engine and parts for it being a 1972 are scarce.

Tire size for what I'm looking at 8 or 10 inch wide by around 22-24 inches tall. I cannot find dimensions for the tires I'm looking at but its pretty close to that size. So a large gear off the engine is that what your saying?

 

[OzFab]

As a guide, 6:1 is a good compromise or "best of both worlds" ratio; for what you want to do, I suggest somewhere in the ballpark of 12:1 which will only give you a top speed of around 10-15mph but, you'll have bucket loads of torque...

To achieve such a ratio you need the smallest sprocket that will fit on the engine, the largest you can find for the axle &, possibly, a couple inbetween

 

[firemanjim]

Off the axle.... Bigger axle sprocket, slower you go, but you can pull more weight. That's what you want. Once you find your tire size, use or he ratio calculator to figure what best suites your needs. Use a jackshaft and drop down to the neighborhood of 11-12:1..... You will pull trees down....... LoL post pic's of the trans. You might be able to use it.....

 

[frdtrkrul]

The tractor is going to be a narrow front, meaning the front tires are next to each other with about a 10* angle. 10-15mph is a bit on the fast side. At the very most 3-5mph would be on the fastest I would want to go at full throttle maybe a bit faster but not by much.

Widest it'll be maybe 3-4 feet wide maybe a bit more. The frame 14-16 inches wide. Overall length my guess about 6 or 7 feet long. Most of the weight will probably be in the front over the tires to keep it from lifting off the ground for towing (happened once and was not fun) may add counter weights like a cinder block. Hope this gives a better idea.


I have to find the trans first. Might have junked it a couple years back. Probably buried under a foot or more of snow right now or rusted out. I know that when my dad got the lawn tractor it was out of about 16 years ago reverse never did work. Had my cousin work on it but he never got it to work. Fast forward about 9 years and my friend and I tore the tractor apart to turn it into a go kart and I think the transmission became FUBAR afterwards.

But yeah I'll try posting picks of it tomorrow.

Also the frame is going to be 1/8" thick angle iron. Engine will probably be bolted down to a 3/16" sheet of metal. 2 brackets made out of angle iron will be used to hold down the battery (car battery for extra power for cold starts during the winter).

Has anyone who used an engine with electric start off a battery how did they keep it charged while using it for lights? I thought about running a small alternator off a car to the engine and doing that but I haven't heard anyone doing this with success.

 

[frdtrkrul]

I've heard people snapping #35 chains, I was thinking of using a #40 or #41 chain. Would these be strong enough for what I want to do or would I end up breaking a lot of gears?

 

[firemanjim]

Hey, you are gonna want like 16:1 ratio, and will have to use a jackshaft. I like that style tractor. Post lots of pics. For the torque you are gonna have, #35 won't work. #40-41 is still kinda pushing it. I would use 420 or 520....
If your engine is electric start, chances are, it has a built in alternator putting out like 5amps, enough to charge a battery. If you only use lights at night, you should be fine cause you would normally drive during the day. Use leds, and you won't need to worry about it.

 

[frdtrkrul]

I've have a pair of halogens that I may use or I may buy a different set that are LED. The style I'm going for is something near the John Deere model A. Could you give me an idea of what tooth count on gears to go with? Most of the sprockets I've been finding only go up to a 40 or 41.

The calculator I've been using doesn't exactly tell me what the ratio is just tells me the final ratio. When I put in 12 engine 28 jackshaft in 30 out and 120 axle it gives me a 9.33 as my final. Not sure if that's even close to what I need. This is what I have been using http://www.fasttrackraceway.com/calc/

I feel like such a newb right now trying to figure this whole thing out.

 

[supermanotorious]

does anyone have a good link for a cost effective 3 speed differential?

 

[frdtrkrul]

Haven't found one or seen one. Best I can come up with is a single speed http://www.mfgsupply.com/gomini/gominiaxles/gominiaxlesgearbox/218390a.html

Of you pull one off a garden tractor from back in the 90s or earlier before everyone changed to hydrostatic

 

[frdtrkrul]

Having a bear of a time finding the right engine sprocket. Can't find much for a 420 chain. But I have found the sprocket for a #41 chain. The 41 and 420 are nearly identical except the 420 has a slightly larger pin diameter compared to the 41 but only by a 1/32" will this be a huge difference? I'm looking at an 8 tooth but its listed as a 40/41 chain and not a 420.

 

[frdtrkrul]

Found the transmission but its frozen to the ground. Took me a bit to find it under 2 feet of snow.

 

[rmm727]

This guys site will give you some ideas.

http://www.cubcadetman.com/content/

 

[qtband]

You could go with a 50 chain. It's pretty heavy duty. You can get a 9 tooth sprocket at McMaster.com. Other sizes, too.

 

[frdtrkrul]

40 seems to be a minimum and 50 would probably be my max. I wonder would doing an encased chain with an oil help the chain any or would running it dry be fine? This is probably outside the realm of go karts, but figured I would ask.

Here's where I originally got the idea from so all credit to this guy: http://www.mytractorforum.com/showthread.php?t=165477

Course his is only pulling a small trailer around where as I'm working this thing, plowing a small garden, plowing snow in the winter, moving a boat around, moving an Ice Castle fish house and other fun things of that nature.

 

[rmm727]

Thanks for the link. I've enjoyed ready thru that as much as the page I posted.

 

[frdtrkrul]

Both are great reads. I finally got my old transmission dug out from the snow today. Have to wait until all the snow gets off. Probably won't be until tomorrow I can take a few pics of it and probably won't be until later this weekend I can tear into it. From what my dad told me, when my cousin worked on it he said some of the gears were worn down. So I probably wont reuse it on this. Plus I would have widen the axle shafts on it and put either a 4 lug or 5 lug hubs on it to accept different wheels.

Not having any luck on finding Agriculture tractor tires for this so I may go with small truck tires for like a Ford Ranger. Front tires for this is easy, going to use garden tractor wagon tires that are roughly 13-15" tall. The front axle I just need to cut it up and put a 10* angle on both halves and weld them to a piece of pipe.

I am concerned though that my design might be too light. So I may have to build it out of 3/16" thick angle iron to get the weight. May go with a custom aluminum gas tank. I'd like to have maybe 1 gallon.

 

[firemanjim]

Why not put the hitch on the front? Makes putting the boat up easier, especially when you're alone, after fishing....

 

[frdtrkrul]

I might do 2 one in the front and back. Once I get the transmission apart I'll decide from there if I am going to use it. Never looked into it but I know when Northern Tool and Equipment was selling Go Karts about 5 years ago for sure, a few models had what's called a Hydrostatic transmission (forward and reverse). Something like this may do the trick http://www.mfgsupply.com/gomini/gominiaxles/gominiaxlesgearbox/218390a.html anyone ever used one on here and have good luck with it?

Not much of a description on it so I don't know if I'll blow it out working it hard.