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ghostofChrist

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Hi all, my friend and I are mechanical engineering majors in college, and both of us work in the construction industry (for now). Neither of us have much engineering experience, we are both freshman in college, but we decided to combine our love for building things and cars and came up with the idea to build a go kart. Now we need some help with frame design, we have a design we took off of google, but we question its strength. Some info on the kart we are building, its a street shifter kart. Since we just happen to have a Kawasaki ninja engine laying around, we are building it around that. We are taking this step by little step, learning along the way. We know our way around fixing engines and a few car mods but that's it. I can weld and do some pipe work but not much more.

My specific questions are: Frame design- Can anybody show us a design or give us some tips on a frame that is strong enough to handle up to a 90 hp engine that's built mainly around cornering made only from straight pieces of metal? We can cut angles but we aren't master metal workers and it would be difficult for us to curve and bend our steel.

Second: Are go kart axle bearings and kits like you would find at go kart supply strong enough for this kind of power?

We are building this around handling but also to accommodate this engine, so what kind of suspension setup should we use? Live axle?

I apologize for the post being all over the place and asking so much, we greatly appreciate any help you are willing to give. We understand this project is likely way over our heads but we figure worst case scenario, we already have a lot of the material and we fail at least we gave it our best shot. This project is meant to be a learning experience with a fun, useable result. As previously stated, we have mechanical experience, we have SOME metal working ability, and we are pretty good with using a wide variety of tools. We would rather spend some extra money on something that's going to work well with this build to make it as safe and doable as possible than to cheap out and do this on a tight budget, so if we need something we will get it. Again thanks a ton for any input.
 

itsid

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My advice.. DON'T!

90HP on a home built frame made my "not experienced metalworkers"...
that's like asking for a Darwin Award!

One mistake one faulty weld and you meet your username sooner than you'd like ;)

just my .02 ;)

'sid
 
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Welcome to the forum!!
First of all, read this:
http://www.diygokarts.com/vb/showthread.php?t=25081
Second of all, this is no joke and not for messing around. You really shouldn't be using an engine like that until your 9 or 10th kart because it's SO dangerous. I cannot stress that enough. What your building will most likely be more dangerous then a ninja on the street with 95 year old ladies in every car. The choices that you have now through building is whether you want the 95yo ladie situation in the middle of NYC, or in the middle of nowhere. Basically, it's going to be very dangerous no matter what is my point. That being said, take this very slowly, step by step, and be very careful.

Sorry, thats all i can really help with. When others come they will tell you exactly what to do. For now, read that stickie, and maybe others; theyre very very helpful.

Ugh, this is not a smart idea in any way. 90hp is TOO much, plain and simple.
This will be very expensive. Your going to need the strongest steel, the strongest this, and the strongest that etc etc. You will not really be able to use any go kart parts for this. For example, you cant use a clutch and sprockets from a go kart. You need a full motorcycle tranny.
 

ghostofChrist

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I appreciate your input. I know everyone on here is going to say don't. Im a pretty experienced welder and definitely trust my welds, what I meant by not experienced metal workers is we probably wont be able to do anything you would need to do with a lathe or make with a forge and anvil. We assume we can bend our tubing just like we do with emt pipe. This project is going to be done regardless, we just want to make this as safe as possible. What if we got a less powerful engine, say 50hp? We know a guy who would buy our current engine.
 
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I would go with like 35HP... Tops!!
For a first build...
I can know every single thing about building a building in my head, but I'm not just gonna launch straight into a full sized house with NO first world experience. I might start with a shed...
You're trying to start with a mansion at 90HP. 35HP is still a small house IMHO.
Sorry for the awkward comparisons, just trying to explain in a friendly way.
 

ghostofChrist

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We are using 1" 4130 tubing with a .083 thickness. We were told this would be strong enough by a couple of engineers on a different forum. We are aware standard go kart parts wont be strong enough, and have the motorcycle tranny. It would probably be a near 2.7lb/hp ratio, which is a lot, we know. The only parts we are truly worried about is axles and suspension. We aren't too terribly worried about the frame but a newer design probably wouldn't hurt.
 

itsid

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there's no point in changing a 90HP for a 50HP engine...
the difference is like being hit by a 2.5 ton truck vs a 4 ton truck...

Aaanyways... well then.. BUY plans;
honestly, go and find a full cage kart you like and buy the plans...
that'll be like 40 bucks or something,
and such plans are more reliable than anything you can come up with (or me ;))
And it keeps you safe.

Make sure you have matching brakes, 4 hydraulic discs.. nothing less than that in a proper size (most important is weight of the final kart)
all those topics are covered in a good set of plans as well.

'sid
 
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Yeah again... This is still over the stop. At this point i would use full buggy or car suspension and axles. Maybe like a legitimate car axle... Then you get the differential too... That would require alot of fabbing to get the ninja engine to the car axle though.
 

ghostofChrist

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How does a go kart compare to a car with a similar power to weight ratio? I haven't driven a car with a 3lb/hp weight ratio, but we've driven cars that weigh 2900lbs with 500+hp so that's nothing new to us. We will probably end up going with a smaller, less powerful engine, but given our car experience, and tool experience, it will still be a little on the wild side. 35 hp is probably a good area off of your advice. We said safety is our first priority when it comes to driving this thing so be it. Where can I find a good, solid frame design?
 

ghostofChrist

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there's no point in changing a 90HP for a 50HP engine...
the difference is like being hit by a 2.5 ton truck vs a 4 ton truck...

Aaanyways... well then.. BUY plans;
honestly, go and find a full cage kart you like and buy the plans...
that'll be like 40 bucks or something,
and such plans are more reliable than anything you can come up with (or me ;))
And it keeps you safe.

Make sure you have matching brakes, 4 hydraulic discs.. nothing less than that in a proper size (most important is weight of the final kart)

'sid

thanks for the answer! We will be going with a smaller, less powerful engine for safeties sake. If that means buying plans for a frame, no problem. Im looking for plans for sale, but most of the ones im finding are for small lawnmower engine type karts or off road karts. This is more of a shifter/racer kart, any suggestions for where to look?
all those topics are covered in a good set of plans as well.
 

n3480h

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It's difficult to be positive in this reply, but maybe I can at least be helpful in your decisions. First, you will not succeed in bending appropriate steel tube (NOT pipe) in an EMT bender. It WILL kink or flatten in the bend. I think if we're talking high HP, we can eliminate most common materials and go directly to 4130 (normalized condition) chromoly tube. Mig welding is not recommended, Tig is ok, but you may have to heat treat after welding to relieve localized stresses. The frame design will require trussing to minimize flexing in all three axes. Then with the potential for high speed (and a sudden unplanned stop) you'll need a roll cage strong enough to withstand ~15G forces - so your body doesn't have to. If you've got REAL money, you might get it done. But the advice given above by itsid and Young One is based on other's documented experience - and it's valid. There are better kart building options that may allow you to live long enough to become engineers.
 

ghostofChrist

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It's difficult to be positive in this reply, but maybe I can at least be helpful in your decisions. First, you will not succeed in bending appropriate steel tube (NOT pipe) in an EMT bender. It WILL kink or flatten in the bend. I think if we're talking high HP, we can eliminate most common materials and go directly to 4130 (normalized condition) chromoly tube. Mig welding is not recommended, Tig is ok, but you may have to heat treat after welding to relieve localized stresses. The frame design will require trussing to minimize flexing in all three axes. Then with the potential for high speed (and a sudden unplanned stop) you'll need a roll cage strong enough to withstand ~15G forces - so your body doesn't have to. If you've got REAL money, you might get it done. But the advice given above by itsid and Young One is based on other's documented experience - and it's valid. There are better kart building options that may allow you to live long enough to become engineers.

We already have 4130 tubing. We are tig welding it, and yes we are putting a roll cage, regardless of power.
 

karte_m0lim

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With that engine I would looking for some singleseater ( formula 1 or indycar style) plans...

Build monocock, mount engine in some kind of cage, add wings and fly...
 

firemanjim

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What you NEED to do is sell that engine and use the proceeds to buy 2 125cc dirtbike engines and the rest to buy standard kart supplies. Build 2 sic street karts on a budget. That way you both have a ride and you can race...... :lolgoku:
You're :welcome2: for that idea.....
On a side note, a 125cc dirt bike engine can push you into the 60-70mph range easily.....
 
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