Mow-Kart

[aidantandy]

Hi Guys,

Thought I'd post a quick update on the progress of my little machine and that starting a project log was the proper way to do it.

The back story is that a couple months ago myself and two of my uncles-in-law cooked up the idea to have a lawn mower race. The only rules we decided on were that the machine must have originally been a lawn mower and that the cutting deck must be removed for the race.

I've been looking for a project like this for a while, because I'm a total newcomer to this sort of thing and I'm keen to learn. And because I'm a total newcomer, whereas these guys have both done this type of thing before and have sheds filled with stuff, I figured I needed and edge. And that edge was to exploit a loophole.

So I found a little Go Kart for sale on Ebay (shown in the first pic) that actually came from the factory with a cutting deck fitted. Not a traditional lawn mower but technically a mower none the less. So after a few weekends work I've almost got it ready for next weekends race.

With the help of some friends here are the modifications I've made so far.

- Removed the cutting deck
- Inverted the pulley driving the wheels so that the bigger wheel is now driving the gearbox rather than the cutting deck.
- Replaced all four wheels with much bigger ones. I think the old fronts were 10 inch and rears 13 inch. The new ones are all 16 inches, although as you can see from the pics the rears are much wider. Because of the time and budget constraints we chose to weld the old rims into the centres of the new ones rather than fabricate hubs or wheel adaptors. The fronts fit in without any drama but we had to cut down the rears a bit to get them in there.
- Welded a piece of bar into the front steering setup on either side to stop the wheels rubbing at full lock.
- Found 5 mins this afternoon to spray the front wheels with some aluminium paint to cover up the marks made by the welding. I call this my 'hillbilly bling'. Apologies to any actual hillbillies reading.

As a result of these mods the mow kart's top speed has increased from 11 km/h from the factory to (an iphone measured) 35 km/h this afternoon. Still not a weapon but certainly fun enough for me at this stage. Ride hide is also increased which is good and the bigger tyres absorb some of the bumps.

Here's what I'm hoping to do before next weekend.

- Pop rivet some metal sheet underneath the seat to protect my backside from any nasty surprises like sticks or rocks I might run over.
- Alter the angle of the gear lever so that the most forward position is neutral rather than reverse. This way if I need to put it in neutral in a hurry I can just slam it up there and don't have to worry about going into reverse accidentally. Obviously this means losing access to reverse but that's a price I'm willing to pay.

And finally a question for everyone:

- The kart has chronic understeer, if I'm not leaning as far forward as I can there's very little weight above the front wheels and it just doesn't turn. Any clever solutions for this?


Almost more than the actual race itself I'm really looking forward to seeing what the other racers have come up with. There's sure to be plenty of Top Gear style hilarity involved when we all get to find out the direction that each of us has taken.

So thanks for reading and even more thanks for the advice and inspiration this forum continually supplies. It's a great group of people.

 

[B man]

add weights up front. like a little rod to hold liftting weights.

 

[aidantandy]

Forgot to mention that I also removed the governor on the little Tecumseh 6hp.

 

[B man]

you do know if they use traditional riding mowers there gonna smoke you. they will have bigger wheels and bigger engines . even 6 speed trannys. by the way how big is your engine? but good build!

Edit: never mind. removed govener. your gonna murder them. straight pipe it add a better air filter and re jet the carb.

 

[B man]

and is this going to be an oval track?

 

[aidantandy]

Yeah you're right B man, power is not my strong point. But I'm hoping whatever disadvantage I do have in power will be made up by having better handling, a whole lot less weight and lower centre of gravity.

And the track is over pretty rough paddock terrain.

 

[B man]

but you can have better power to weight! mod the engine! straight pipe, high flow air filter,and re-jet carb. you will leave them in the dust!

 

[Doc Sprocket]

Regarding the shifter- while reverse isn't all it's cracked up to be, you may not have to lose it. Have a look at the way the linkage works- usually in a straight line, and the "gate" creates a pattern of sorts. The gate is just the metal plate the shifter passes thru and is notched to hold the shifter in each gear. Now that you've looked at it, you can probably alter it to allow you to "slam" it into neutral and yet still achieve reverse. Perhaps cut a plate to fit on that requires you (from neutral) to move the handle a bit sideways and then forward again to hit reverse. Other ideas may work, too.

The understeer will be hard to counteract, especially with a tight time frame. You can add weight to the frontend, but I would caution you to take it easy. Weight, of course, will hurt speed. You could rework the frontend geometry, but that would take time. In your list of mods, you did not mention the differential. Most mowers have one to allow better steering, and less damage to the lawn. Did you alter or defeat yours?

 

[aidantandy]

Toystory I agree with you as usual. The thing is that any of those high quality gear changing solutions you suggested are unlikely to get done before Saturday's race. We're in the depths of winter down here in my part of Australia and I don't usually get home from work till 6:00 ish when it's dark and cold so working when I get home is unlikely.

However I'm looking at this weekend's race as the beginning of the adventure with this Kart. All these changes can be made later. When there's more time.

I'm hoping that unbolting the gear lever when the kart is in neutral and rotating it forwards to the most forward position will be a temporary and reversible (pardon the pun) solution that I can acheive relatively easily.

I left the diff unaltered. To be honest I pretty much forgot about it. Do you think it might be an area where I could get more performance? Hmmmm very interesting.

 

[anderkart]

- The kart has chronic understeer, if I'm not leaning as far forward as I can there's very little weight above the front wheels and it just doesn't turn. Any clever solutions for this?

Yeah, move your seat forward, dont add any ballast-weight, you are all the ballast you need or want.

You'll want around 40/45% of the total kart/driver-weight on the front wheels. (and also a 50-50% side to side bias, you can also re-locate the seat over to the side a bit to correct this)

Take your seat bolts out, and rig up 1 or 2, 3 or 4 bathroom scales to actually measure your weight distribution. Make sure the kart is always level during the scaling process. unless you have 4 identical-height scales, shim the other tires up off the ground so the karts stays as level as possible. (find a level portion of your kart and use some type of carpenters level while scaling to confirm this!!!)

Just figure out a way to move around on your seat to find the best weight-bias location, then mark that spot and securely re-mount your seat. It looks like your seat needs to go forward a bunch, so I'm not surprised it doesn't turn very well now.

You'll probably also be able to further adjust more/less steering ability with your tires air pressure. You could drop the air pressure in the fronts/use higher pressures in the rear for improved front grip/less rear.

(but if your tires are tubeless, dont go too low in the front pressures, or you'll pop the tire right off the bead while racing. You could carefully drill 3 small holes through the rims bead and use sheet metal screws with silicone on the threads into the tires bead as a free/DIY-beadlock system...)

Your beadlock screws should reach 3/4 of the way through the tires bead, not all the way through...

 

[#28 FASTGRASS]

Cheap understeer solutions?

The understeer will be hard to counteract, especially with a tight time frame. You can add weight to the frontend, but I would caution you to take it easy. Weight, of course, will hurt speed. You could rework the frontend geometry, but that would take time.

And finally a question for everyone:

- The kart has chronic understeer, if I'm not leaning as far forward as I can there's very little weight above the front wheels and it just doesn't turn. Any clever solutions for this?

mmm If you can space out the width of the front wheels and bring in the rears you can tune the thing to handle a whole heap better. You will "dial" out the understeer. If you can make up some axle front spacers to slip over the axle out of pipe etc. have a go! You might be luck enough to just loosen the rear wheel hubs and sneak them in a mile
Dont have to add all that useless power robbing weight either
Can you move the seat forward? this will help too???? which ever is easy try first!

 

[landuse]

I think Anderkarts suggestion of tyre pressure is a good, fast and easy way to correct the steering somewhat. Seeing as you don't have much time, just do that.

 

[aidantandy]

Thanks guys

The seat does move forward so for this weekend I'll probably just go with that. It means I'll be a little cramped (I'm 6'3) but it's not too bad. Just feels like I'm a WRC driver, sitting super close to the wheel.

Got a call from one of the other guys in the race saying he'd spoken to the 3rd competitor and that he has some sort of transmission problem (permanently stuck in reverse apparently) and he wasn't sure if he'd have a functioning vehicle in time for the race.

I'll be so bummed if he doesn't. Have been looking forward to this for aaaaages and while 1 on 1 racing will still be good all 3 of us going around and dodging and weaving would be much more fun.

Would not be surprised if there's a bit of playing possum going on here though. I wouldn't put it past this guy at all to pretend not to be ready just for gags and then show up on the day ready to go.

 

[landuse]

A one on one race wouldn't be as nice, I agree. Maybe you could postpone for a week, and do it the following weekend.

You definately have to post some pics of the other karts after the race. I really want to see what everyone came up with.

 

[aidantandy]

Does anyone know what sort of fluid I should use to lubricate the gearbox on my cart? Is there such a thing as ride on mower gearbox oil? After a bit of googling I'm still not sure.

 

[landuse]

As far as I know, you just use regular transmission oil. Read this

http://en.wikipedia.org/wiki/Gear_oil

 

[landuse]

I was just looking at the pics of your kart again, and it is really cool!! You will have some fun with this for a long time to come.

I hope the race goes well. SMOKE EM!!

 

[anderkart]

Does anyone know what sort of fluid I should use to lubricate the gearbox on my cart? Is there such a thing as ride on mower gearbox oil? After a bit of googling I'm still not sure.

I couldn't find the operator's manual for your Wolf Gaten Ride On Lawn Mower Go Cart Model. But if yours has the same type of Hydrostatic Transmission as the Wolf Gaten Ambition 107.175 H Lawn tractor model, You might find your answer here in this link:

This manual is in like 10 different languages, so good luck
http://www.wolf-garten.co.uk/fileadmin/6_Manuals/13TN79RG650.pdf

If that manual isnt any help, you should try calling/emailing the manufacturer and ask them: http://www.wolf-garten.co.uk/index.php?id=856

 

[aidantandy]

So here's how race day went down. Both my wife's uncles arrived with traditional ride on's. One of them had a Briggs 12.5hp but unfortunately he just couldn't iron out his mechanical problems during the day and his mower kept cutting out when driving down hill. The other uncle arrived with a 250cc bike engine installed. The thing was a beast. Smoked everything else easy. Burnouts, a little wheel stand action it was a serious machine.

My thing went ok but I'm kinda kicking myself for not doing more practice driving because I would have noticed how much it struggled up hill. Seriously it really struggled which sucked. But downhill and on the flat sections it was great. Actually downhill it was as fast as anything else. The combination of the switched pulley and bigger rear wheels was just too much, I over geared it if that's the correct term. If I had done more driving I could have switched the pulley back, giving me a bit more acceleration. Oh well there's always next year.

Now I know what you're thinking. Where are the photos and video? Well about that. Right now I'm laid up in bed with a couple ice packs because I had a bit of an accident. Tried to take a corner too fast and crashed. Bumps, bruises and grazes only thankfully. So I'm too sore to go grab the camera, will upload them in the next day or so (apparently there's even footage of my stack which should be good for a laugh)

So even though my competitive streak won't let me be completely happy with not winning and I'm annoyed how slow my cart was uphill it was still a great day. Had about 20 people show up (in fact when the uncle with the bike engine said he was bringing some family I should have twigged that he had something special) and there's already talk of where to hold it next year.

 

[aidantandy]

Forgot to say thanks again to everyone for the advice and assistance.