24cc Deer Kart Build

[Weedge1212]

Hello everyone,

The project I am currently working on is a motorized deer kart. I have a 24cc 2-stoke engine off of a stihl weed wacker. Although this is not a trike or tandem, i am hoping this is the right place to post this build. This project is not yet completed and I am posting it here to get some tips along the way. Here are some pictures of the cart itself

I got this kart off of craigslist for $40. Which I thought was a great deal. The kart is much more heavy duty than a lot of other ones I've seen. It also came with the hand crank winch attached which I thought was an awesome feature. I intend to have my chains and sprockets positioned so that I can still fold the kart up for transportation. I would like to use this kart for hauling deer out of the woods but it will probably be used more for hauling beer and gear in and out of camp.

The stihl trimmer was being thrown out so i grabbed it and got the engine running. The engine only needed a carb cleaning and a new primer bulb. I saved the engine, clutch housing, and throttle control with a kill switch. The rest of it I threw away. So all together I have about $45 into this. I am trying to keep this project as cheap as possible. I got some scrap angle iron for free that I am going to use for mounting the engine and creating a mounting bracket for the jackshaft. I also have some axles from a riding mower than I plan on using for the shaft of my jackshaft. But I know the sprockets, chains, pillow block bearings are going to be my main cost (none of which i have ordered as of 6/1/18). I have to include a jackshaft to get the gearing low enough. This cart only needs to go walking speed and not much faster than that. So here is a sketch up I did for the drivetrain and gearing plans.

I used a gearing calculator https://www.electricscooterparts.com/motor-jackshaft-wheel-gear-ratio.html to determine the sprocket sizes I will need to achieve a speed of about 3 MPH. The engine idles at 2800 rpm. So I assume the clutch will engage at 3000 rpm, or atleast close to it. If I use sprockets with 9 teeth to 72 teeth twice, clutch to jackshaft and then jackshaft to wheels, it will go about 2.8 MPH. Just slightly under the 3 MPH I was shooting for. I was able to find the owners manual online and that says the engine has a max of 7,700 RPM. So at 7,700 RPM it should be going about 7.18 MPH. Which is close to running speed. This comes out to be a 64:1 gear ratio. I figure this will give me a good range of speed all the way through the throttle. If someone knows of different gearing that would work better than please let me know.

One thing I'm not completely sure of is how I am going to attach the sprockets. First off is the clutch.

As you can see in the pictures, the clutch drum has a square hole. So I suppose I just need to find some steel rod that i can square off on my bench grinder and use a type B sprocket to attach it to the squared rod. This rod also has to be strong enough not to twist or bend when this kart has a deer on it and an engine spinning at 7,000 rpm. Which make me question if this is the way to go. If any of you guys have a better suggestion on how to attach the sprocket to the clutch, please let me know.

I also question if this clutch will be able to handle the load of this kart. I don't know for certain, but i don't think this kart will have much more than 150 lbs on it. Again, I'm sure someone on this forum has a lot more experience with these centrifugal clutches than I do. So if this clutch is just going to start slipping the minute I put some weight on it, than please let me know what modifications I can do to it or if I should look into something completely different.

The other sprocket that I am unsure of how to mount is for the wheels. Although this kart does have a solid axle, it is not set up to spin. There are no bearings where the axle mounts to the frame of the kart. The wheels spin freely while the axle has a codder pin going through it to keep it stationary. The inner diameter of the wheel hub is round and does not have a cut out for a keyed shaft. Because of this, I decided it would be easiest to attach a sprocket to the hub of each wheel. Here is the 20" wheel/ tire that I am using.

At first i was planning on drilling right through the sidewall of the wheel hub and bolting a flat style sprocket to the side of the wheel closest to the frame. But after some research I found out about clamshell, pineapple, and rag joint hub adapters. I've found that members on this forum use all different types of methods for attaching sprockets to wheel hubs. I am not entirely sure what is the best adapter for this build. Although the outer diameter of the wheel hub is round and doesn't taper, the spokes are not aligned in the pattern that most bicycle wheels are. They are spaced out much more and I don't really like the idea of clamping a mounting bracket that is going to put excessive stress on the spokes of the wheels. What do you guys think? Would my original plan of using bolts through the side of the hub to mount the sprocket work or should I consider purchasing some type of clamp for the outside of the hub?

Well its starting to get late here and i think I've made this post long enough. I am completely open to any suggestions or tips that you guys can give me. I will keep this thread updated as my work progresses on this build. thanks in advance to anyone willing to read all of this and provide advice.

 

[curtisfox]

KOOL ! Take a look in staton inc , they have gear boxes that may save you a lot of chain and sprockets........Curt

 

[Weedge1212]

Thanks curt. I did find out about staton inc from a post I read during my initial research. They have a lot of the parts I need and what seems to be decent prices. But I just searched for gear boxes and it seems the greatest reduction box I could find is 18.75:1 ratio. Which is only 1/3 of the reduction that I need. And they are also upwards of $130 after shipping. That is way out of my budget and cant see myself spending that much on 6 sprockets and a couple yards of chain.

 

[dogcatcher]

Just to make sure I understand, are you trying to make this cart motorized so you only have to guide it as it pulls itself along? I like the idea, kind of like a self propelled lawnmower. But I would make it a 3 wheeler with a single from wheel that free pivots. Or make a tiller type steering system with a single wheel in front so that you could ride on it when not hauling.

 

[Weedge1212]

Yes. My intentions are to make this kart somewhat self propelled as I pull (not pushing it forward) it behind me as I walk and guide its direction. From a few different builds I've found on this forum, I've learned that I will likely still have to pull the kart with my own strength until I have it rolling and some momentum before the clutch will engage without slipping and let the engine take over to power the kart.

I will be using this kart in the mountains. I plan to haul gear, food, drinks, and other camp items up very steep trails that will be far from smooth ground. The only time the kart will be close to empty is when I'm leaving camp and heading back down the mountain. I really have no desire to ride on this kart. The type of trails I will be on would only be suitable for something with a full suspension and brakes. Maybe one day I will decide to build a motorized bicycle or trike, and of course post it to this forum. When that time comes this project will have given me great understanding of the challenges involved in doing so.

The idea of installing a third wheel in the front of it is interesting though. I'm sure that would help with some weight distribution and put less of a strain on my hand and wrist as I pull the kart behind myself. I will give this idea consideration. Thanks Dogcatcher.

 

[fasteddy]

One problem I see is the wheels you have are made for push carts. The spokes are held in with the folded over rim and any amount of power allied to the wheel will loosen them up in short order and pull them out.

You will probably need heavy duty bicycle wheels with 12 gauge spokes to handle the strain.

If you look at go kart parts sellers you will see sprocket mounts that clamp on the jack shaft and the sprocket mounts to them. This will help with the build.

Steve.

 

[fasteddy]

Here is what I mean https://www.bmikarts.com/Azusa-Aluminum-Hub-34-Bore-with-1680-Bolt-Circle-_p_3821.html I found this on B.M.I. Karts and Parts and Go Kart Galaxy has the same things and an excellent choice of sprockets. My two main go to places for parts.

BMX front hubs have 6 bolt holes for disc brakes. Using a brake disc as a pattern you can drill holes in a blank sprocket {no holes other that the center hole for the axle} and use the brake holes to attach the sprockets to the hub.

Many BMX hubs have 20mm pass through axles or just over 3/4". You will have to put a single wrap of pop or beer can around the axle to take up the little bit of slack. The hub slips onto the axle and has sealed ball bearings in it. If your axle is 5/8" you shouldn't have any problem finding a through hub in that size I'm sure.

In the end you may well find that the Staton set up is worth the money when you factor in the time and parts cost.

Hope this helps.

Steve.

 

[curtisfox]

Hi! Steve
The cart wheels do have 12 gage spokes and 3/4” axles, at least the ones I have seen do. They are also used on 1903 olds repilica cars, that are lawn mower powered through lawn tractor transmissions. So I think he will be ok as his speed is so slow, like that hub link.
Weedge1212 iyour clutch should be good, with your low gearing it should engage right away will be at high rpms very early on, to engage....... Curt

 

[fasteddy]

Just thought to put the photos on magnification and the spokes do go through the hub. Probably best to drill through the side of the hub and out the other side and use washers to hold the sprocket off the hub so it clears the chain. Looks like a fun project.

Make moving the 12 point buck easier.

Those sprocket hubs make mounting sprockets on jack shafts easy.

Steve.

 

[Weedge1212]

Thanks for the ideas Steve,

The wheels have been a part that I'm conflicted on. Looking at it from one way, I want to save money and it would be easy and simple to drill through the side of the hub, find some long bolts and spacers, and just mount the sprocket. But looking at it from the other way, I have a set of 20"(I think) BMX front and rear wheels/tires hanging from the rafters in my garage that I'm sure I could buy some parts for to make them work. But I never even thought of using a wheel with a disc brake mount. That would also make things very simple and easy. But if you do think the stock wheels will be strong enough to handle the load, then i will probably just end up using those. Here are some close pics of where the spokes meet the hub. The spokes measure 9/64", I don't know what gauge the comes out to be. Also my axle is 5/8"

Curt, thanks for the reassurance on the clutch. I haven't pressed the clutch drum out of the housing yet but when I do, I'll post some pics and figure out how to attach the drive sprocket.

 

[fasteddy]

Curt's a wizard at building bikes so I'd go with his idea of using these wheels. As he said you aren't going any faster than a walking speed and if the wheels don't hold up or prove difficult to do you can buy the bike hubs and use your BMX wheels.

If you can source a small, light rear axle out of a lawn tractor you might consider it. It will give you a differential so that both wheels can move at their own speed and turns and moving over rocks ect will be easier with less fighting to control the cart. It will fit in with your drawing of the drive train well I think.

Very much looking forward to your build.

Steve.

 

[curtisfox]

9/64 is 10 gage heavier yet, 5/8” axle will be ok if you put mount close to wheel. ...........Curt

 

[Weedge1212]

Steve, I do in fact have a differential out of a riding mower. I was originally planning to use it so the wheels would be able to spin at different speeds. The main reason why I decided against it was if I was using shafts all the way through, I would no longer be able to fold the kart up for transportation. But the more I think about it, I might be able to fit a belt to the ring gear of the differential. I'm thinking like belt drive motorcycles with the type of belts that have teeth. But the differential gears all need to be greased heavily so I would also have to fabricate some type of casing for it all. I'm just not sure if its worth the work hours.

 

[fasteddy]

Could you replace the axle with the rear end? A round steel plate welded to the axles or the sprocket holder bolted to the axle and bolts through the hubs and the plates/sprocket holder to keep the wheel solid. With the proper sprockets or pulleys you could gear it to the speed you want and cut down on the jack shaft.

Keep the motor close to the axle so you can still fold it.

Steve.

 

[Weedge1212]

Steve, it is definitely possible to switch out the solid axle with the differential. But there was a couple reason why I moved away from that idea. First was that the new axles would be 3/4" and a lot heavier. Second, I would have to get different wheels with a key way hub. And third, is that there is no support bar on the frame of the kart where the axles are. So i feel my clearance from rocks would be compromised and if I have something loaded on the kart that might rub against anything mounted in the center of the axle. If you look at where the kart folds, there isn't really a way to mount the engine with out having a bend through the drivetrain. And the higher up there engine is mounted, the less of a chance it will have scraping anything. Anyways, maybe you will have a solution to all this. Here is a pic of the differential I have.

 

[fasteddy]

Do you have the rest of the axle. It should look like this.

https://www.northerntool.com/images/product/400x400/136/1369_400x400.jpg

A sprocket bolts onto one side of the bolts that hold the housing together. Staton sells the different bolt patterns in various tooth counts.

A motor driving the differential with sprockets on the end of the axles going to the wheels or driving directly to the sprocket of the differential if used as an axle would work. With a 3/4" axle a sprocket adapter with the sprocket bolted to it on each end would drive the sprockets on the wheels like a jack shaft. That would allow you to use the 3/4" axles on the differential and the 5/8" axle and wheels.

A 72 tooth sprocket is 9" across without the chain. I have one on the tri car and I just went out and measured it. You will need to consider this when working out clearances. Figure 5" on either side of a shaft.

If you plan on folding the carrier for hauling, how were you planning on mounting a motor/ jack shaft combination?

Looking at the the last photo I would say that everything happening will have to happen on the two pieces of tubing that are bare behind the axle. I'd get rid of the canvas and replace it with some galvanized steel, rust proof , washable and rigid. Deer will slide on it easier as well.
Motor mounted towards the top and then the jack shaft to the wheels for clearance under the carrier.

Steve.

 

[Weedge1212]

Steve, what about the possibility of using non brake coaster hubs with the outer sprockets on my jackshaft? I'm talking about the hubs on most mountain that allow you to petal backwards freely. If I was somehow able to use those with the sprockets that lead to the wheel it seems as though one wheel put turn while the other one is able to move backwards when I have to make a tight turn. I'm at work right now and just brainstorming so I don't know if that idea will work at all.

As for the differential, the casing for it is huge and contains the gearbox from the tractor inside of it. It is very heavy and awkwardly shaped. Here's a pic:

 

[fasteddy]

That's a transmission with a differential axle not a differential axle on it's own.. Now I see what you mean.Moose Armstrong wouldn't be able to lift it for long.
You mean the free wheel on the rear sprocket? Trouble there would be I think that it would be under constant pressure as the motor drives the chain. It would never have a chance to free wheel in reverse.

Without a differential in the mix the problem is that as the motor drive both wheels when you try to turn, the inside wheel doesn't move as fast as the outside wheel and it will bind.
The inside wheel will try to slip on the ground and if it can't the chain will bind up on that side and eventually it will snap the chain or rip the axle or jack shaft off.

One thought I had was finding a 20" bicycle and cutting the head set and the forks off it and welding it to the rear of the cart where the motor would go. Then you could add a motor to the top of the forks and a sprocket to the wheel and have a powered wheel pushing the cart that would pivot as you steered the cart. It should turn in it's own length and with weight on it have good traction.

Steve.

 

[curtisfox]

Steve is right. With the peerless differential both wheels pull, and when you turn it sorta ratchets around the corner. If you look you can find lawn tractor ones eBay, they have offset short axle on one sided, and sprocket can be bolted on either side. ......Curt

 

[fasteddy]

Glad your here Curt. What do you thing of one powered wheel at the rear pushing the whole thing. Powerful enough and good traction?

Steve.