New plans

[user53]

Well, originally I was going to build a "budget kart" and make my project be as cheap as possible. Money isn't a huge issue, but I thought it would be fun to build a kart from junk. I had originally been going to use a lawn mower engine for it. After thinking about it, I realized that was a bad idea. It would have ended up being expensive to build/use.

So, I figure, since it will cost a decent amount of money anyway, why not just spend a little more, and make a good kart. So, I'll be picking up a 6.5hp horizontal shaft, and am going to spend time on it, and build it right, with the right materials. I probably won't start any building for a week or two yet, just making up new plans/getting new ideas now.

Here's what it's going to be...

~7ft x 3ft general size
-8-12" ground clearance
-10-12" tires
-gearbox (from old cycle)
-3-4" suspension movement
-Usage goal - runaround for yard, able to go on woods trails, but still have decent capability for on road (err, pavement) use.

Just thought I'd update what I'm planning. Any ideas/tips? Any input or suggestions would be great. I'd hate to build it, and realize I should have done something different in the design. So, any hints/tips would be awesome. Thanks! I'll post up the CAD designs of the frame/suspension when I get them all done.


I guess I'll explain my purpose for building- My Explorer (my toy) is dying, and I will probably be replacing it with a car. But I really do enjoy offloading/trail driving, and this will be somewhat of a substitute for it. I really would love keep my explorer, but it isn't worth shelling out the cost to repair it. I would also like to get a new one some day, but I can't afford to have 2 vehicles now, and beyond hobby driving I have no use for a truck/SUV, so I'll be going for a car. I'm planning on getting a 3000gt (VR4?) and making it my little race car. But, with the kart, I will still have some toy I can take out in the woods and on the trails. Eventually though, (when I have the space to keep it, and the cash to build it) I will buy a new explorer and continue lifting it/building it from where I am now.

 

[Kenny_McCormic]

Ho do you plan on 12" of ground clearance with 12" tires?

 

[newrider3]

The suspension will take care of that, but it would only be 12" under the main pan.

 

[user53]

I'm talking about the clearance of the frame. The drive axle will be dropped down lower than the frame, and the steering spindles will be on "drop down" brackets, for lack of a better term. Basically, instead of them being welded at frame level, they will be welded on with the arms going down at about a 45 degree angle.

It will be set up like my Explorer. I have 31" tires on it, but the frame/body are ~20" off the ground. Like in this picture, in between the wheels is 20" off the ground (sorry for the blurry picture, just took these with my cell phone)

But, the suspension/axles is not at the same level as the frame, like in this picture. They hang down lower...

True, if I were to drive over a 10" stump with the setup I'm planning, it would hit on the rear axle/spindles. But, when I'm driving over something like a steep hill, downed tree, ect (anything at least as wide as the wheelbase) I will be able to go over fine without hitting.

Like this..

The red represents and obstacle, and the gray is where my frame will be, and the blue line is where a frame would be if it were level with the axle.

The reason is, it allows for taking steeper hills, going over logs, ect. If going through mud and stuff like that, even if the axles are hitting, you will be able to get through better, because the frame won't drag/drag as much.


Edit: Guess the post explaining it before this one was posted while I was typing this post I guess he explained it a little simpler than me...

 

[user53]

Down to the guts. Engine and driveline thoughts?

Alright, now down to the guts.

First off, do you think this will for for the drive line? I'm planning on using a 6.5 HF blue motor. I've got a 1981 Maxim motorcycle, with a blown engine. I'd like to try and use the 5 speed transmission off of that. I'm hoping that way I can have a very low 1st gear, good for crawling, hill climbing, ect, but still have a top end gear that will give a good speed.

So, how much do you think the cart can weigh? I don't know how much the 6.5 will be able to push. I'm assuming a fair amount if I can get the transmission to work.

Secondly, do you think I'll be able to get the motorcycle transmission hooked up? I can't look at it now, because it's 30 miles away in a friends shed. I've never looked at it too close, so I'm not sure how it hooks up to the engine. I know it's shaft driven, which might end up making things easier. Does anybody have any experience with motorcycle transmissions? Any idea on how I could hook it up?

Last question-any ideas for the rear axle? I want it to have both wheels driven. I'm thinking either have a solid axle with a chain running to it, and having the whole axle move with the suspension. Either that, or try and find an old ATV rear diffy and axles, and use that. It would be nice, because then I could do IRS. Any opinions on what would work better with the motor/transmission setup I'm planning? I think if I did a solid axle it would be harder to make the drive line, because it would have to move with the suspension (axle moving up and down). On the other hand, if I had an ATV diffy, it would be easier to hook up the drive line, since it would all be stationary, but it would be harder to make the suspension design.

 

[modelengineer]

Wont that ground clearance make it unstable?

It would be easier to buy a running motorbike which has been damaged (you can get them surprisingly cheap) and use that engine AND gearbox, rather than trying to rig up something with an industrial engine and bike gearbox.

If you use a swingarm rear suspension then you can put the motor on the side with the gearbox output sprocket on the exact centerline of the pivot of the swingarm. That way, as the suspension moves up and down the chain stays the same length. This reduces unsprung weight (a good thing) and you have the motor stationary. It's easier to manufacture than IRS, but not quite as good, however IRS isn't (usually) cheap.

Or you could do it the way you said; with the motor on the swingarm. This would be easier to make, but slightly more difficult to do the gearshift linkages. You would need to use a push-pull gearshift cable, or some sort of linkage that uses rotational movement which wont change as the swingarm moves up and down.

 

[Kenny_McCormic]

You would be better off rebuilding the MC engine that trying to adapt it to an external input.

 

[2or3wheels]

yeah sounds like a tall order, how would you connect the motor to the trans?

 

[user53]

Wont that ground clearance make it unstable?

It would be easier to buy a running motorbike which has been damaged (you can get them surprisingly cheap) and use that engine AND gearbox, rather than trying to rig up something with an industrial engine and bike gearbox.

If you use a swingarm rear suspension then you can put the motor on the side with the gearbox output sprocket on the exact centerline of the pivot of the swingarm. That way, as the suspension moves up and down the chain stays the same length. This reduces unsprung weight (a good thing) and you have the motor stationary. It's easier to manufacture than IRS, but not quite as good, however IRS isn't (usually) cheap.

Or you could do it the way you said; with the motor on the swingarm. This would be easier to make, but slightly more difficult to do the gearshift linkages. You would need to use a push-pull gearshift cable, or some sort of linkage that uses rotational movement which wont change as the swingarm moves up and down.

Unstable? Maybe. It all depends on what you consider stable. And if you are used to the feeling of a wheel lifting off the ground when cornering. The method you mention to keep the chain the same length is what was planning on doing.

You would be better off rebuilding the MC engine that trying to adapt it to an external input.

I thought about that, but since this motorcycle was used as a parts bike, the key engine components are gone. Plus, given how it..died..I'm guessing the block is scratched pretty bad and unusable. It would be cheaper to buy a 100% working cycle than try to make this engine run again. Too many missing/blown parts, and it's too old to get them easy/cheap, if at all.

yeah sounds like a tall order, how would you connect the motor to the trans?

I'm not sure, I was really hoping somebody had done this before, and would have some insight. I'll post some pictures when I get it pulled. Not sure when that will be, but I'm going to try to ASAP.

Even if I can't get it to work, nothing lost, since I don't have to buy the gearbox.

If I can't get it to work, I think I'll just forget my idea for having a transmission, and just go with one gear. I'm just hoping to get the transmission to work, so I will have a super torquey gear, and a top end gear for when I want to move quick.

 

[modelengineer]

I have heard of someone connecting a motor trans to an industrial engine. I think they had to run two chains and they said it was really noisy. Not sure whether you could utilise the manual clutch on the gearbox, might be able to. Otherwise you would have to use a centrifugal clutch and learn how to match the revs on the engine to the gearbox because you will be, effectively, clutchless shifting on everything but neutral to first.

Without taking the gearbox off the motor it is difficult to see how you would connect them.