Mini Monster Truck build

[OFF THE WALL]

Hey everybody, I'm new to this site. I joined because I would like to share my build as well as get some advice if/when i need it. I have been searching around for awhile for an old carter mini monster for my son to no avail, either they have been complete peices of junk or people just want way to much for them for what they really are(a yard kart with big tires and a body. So I desided I will just build my own and model it more after the real thing. So this is how far I have gotten to date. I bought what I think is a body from a mini monster. A 11hp electric start honda clone. And a buttload of 1 1/8" .083 pipe. Check out the pics and see what you think.

 

[OFF THE WALL]

I'm new to forum posts and I can't get more than one pic at a time to post?

 

[Doc Sprocket]

Looks like a good start! Is that pipe or tube? Have you got your driveline figured out yet?

EDIT- The pic thing is because you're new, and getting caught in the anti-spam measures. Once you have a few more posts to your credit, it will go away.

 

[OFF THE WALL]

Body.

 

[Doc Sprocket]

That is a REALLY cute pic!

 

[OFF THE WALL]

Thanks. I guess it would be tube. I'm not sure at what thickness it goes from pipe to tube. Not sure about the drive line. First I have to decide wether I want to go with suspension or not.

 

[OFF THE WALL]

Thanks. That's the little monster. Everyday I hear it now, "is my truck done"?

 

[Doc Sprocket]

The pipe/tube delineation isn't really a thickness thing. It's about the metallurgy, and the way the sizing is rated. Pipe is sized according to Nominal Inside Diameter. Example- 1" pipe has a nominal ID of 1". In reality, it's more like 1 1/8" or so. Actual outside diameter can be in excess of 1 1/4", even though it's called 1" pipe.

 

[OFF THE WALL]

Yeah not really sure. I told the steel yard I want 1" tube for building a go kart and this is what they gave me. The actual OD is about a 32nd under 1 1/8".

 

[OFF THE WALL]

I'm thinking about going with a 4link type suspension just like on the real thing but I'm not sure of how to incorporate the mounting of the motor into that. From what I can tell suspension karts motors are mounted on the "swingarm" as opposed to the frame. If I can figure it all out I would like to do full suspension. Live axle. But again I'm not to sure of what it really needs. I don't want to gear it to go very fast because it is going to be a pretty tall kart and I don't want him to flip it, so if he's not going very fast does it really need suspension.

 

[Doc Sprocket]

Need? No. Suspension is nice, but net necessary for a low-speed kids toy. If you do, a simple swingarm with the engine mounted to it will be fine.

 

[DaiSan76]

Big balloon tires will absorb a fair bit of bumping on their own. If you're keeping it slow enough to keep from tipping you probably won't really need it.

 

[Doc Sprocket]

Agreed. And if you tube them, you can run ultra-low air pressure for more shock absorption.

 

[OFF THE WALL]

thanks for the suggestions. so today i spent a little time ripping parts off of an old shaft driven kawi quad. i don't know if im going to use any of the parts but we will see. i do kinda like the idea of having a "meatball". the shaft to chain might be a little tricky.

 

[OFF THE WALL]

so i've been looking for a while and i think these are my tires/rims. 25x12x10. go big or go home!! lol

 

[OFF THE WALL]

Ok so I ordered the tires and rims and decided I am going to do suspension. Not so much for now but down the road as my son gets older he can do more with it. My question is this. I have no clue when it comes to gearing. Do I need a TC or can I get away with a CC? How many teeth on the final drive/clutch/TC sprocket? As I said before I'm working with an 11hp, and the tires are 25x12x10. I definitely don't want top end speed.

 

[landuse]

Ok so I ordered the tires and rims and decided I am going to do suspension. Not so much for now but down the road as my son gets older he can do more with it. My question is this. I have no clue when it comes to gearing. Do I need a TC or can I get away with a CC? How many teeth on the final drive/clutch/TC sprocket? As I said before I'm working with an 11hp, and the tires are 25x12x10. I definitely don't want top end speed.

With a 11HP engine, you have narrowed your options of clutching quite a bit. A centrifugal clutch with a 1" bore is going to cost you over $100, and if you use a TC you are going to have to get a comet 40 series, because the 30 series is only rated up to 8HP.

As for gearing, with 25" tyres you are going to have to gear quite low. I would suggest at least 7 or 8:1. That means something like a 10T clutch and 70-80T axle sprocket. If sizes become a bit unrealistic due to ground clearance, you might have to use a jackshaft.

 

[DaiSan76]

You will want a jackshaft. When built my kids Kart, I had it at 33:1 with 15 inch tires and was doing about 5mph.

I put some numbers in the spreadsheet and came up with this.

7:1 will net you 40mph, which is a bad idea for a tall, kid driven rig. imho you want the right side of the picture, if you can find the sprockets you need to do it. Also, if you can afford it, a Torque converter will allow you to set the RPM lower, and get a lower speed without burning up the clutch.

 

[OFF THE WALL]

What I would like to do I something along The same lines as the suspension. I know he doesn't need suspention or for it to go fast now but in the future I would like to be ableto have the option without having to spend more money or fabricate more parts. I plan on putting some sort of a mechanical governor, whether it's at the pedal or a stop on the butterfly for the carb. I would rather not dish out the money for the torque converter, if I have to why will. What is the benefit of the jack shaft aside from reducing the size of the drive sprocket?

 

[DaiSan76]

A properly made jackshaft will allow you to quickly and easily adjust the gear ratio as well as reducing the size of the driven sprocket.