Thunder Kart Project

[jamyers]

I started out with a Thunder Kart, and ended up with an 8hp electric-start, live-axle "El Terror de Tejas". Lotsa fun, but like said above, they're not made for much over 30-35mph - which truthfully is plenty fast even for a speed-freak like me, and that's after low-budget some steering mods. I've reinforced the frame in several places, and repaired breaks/cracks in several others. See my build thread in my sig for details.

But it works, and the DIY is what it's all about, yes?

Safety Fast!

 

[Pocketrocket]

I was thinking of modding the frame to do a live axle conversion and putting some suspension on the front, as far as the live axle do you have any tips because it looks pretty straightforward to me ?

Thanks man it's good to know somebody else has done something like i've been having in mind

 

[jamyers]

The live axle was pretty straightforward, I picked up some high-quality pillow-block bearings at a local bearing supply for about $20 each, if I remember the price. Drilled through the frame and bolted them underneath.

We did lengthen the frame and kept the original stub axles, they're kind of handy as lift points and tire guards. Mounted the live axle behind them, with the battery on the old engine pad in front of the new engine. The first couple of pics in my build thread show the layout.

As far as the front end, basically all I've done so far is heat and twist the arms coming out from the frame to lean the king bolts toward the rear. Originally, one was straight up (0* caster) and the other one was leaning WAY forward (like 15* neg caster), which made it extremely twitchy and hard to keep straight. I bent them both back equally to about 10* positive caster, which makes it a lot more controllable and easier to steer at speed. Next I plan to re-work the front tie rods, moving one to the other side of the steering-wheel arm so and "crossing" them over each other to gain some "ackermann" (increasing toe-in when turning) effect.

 

[Pocketrocket]

Yeah i thought the live axle would be pretty straight forward but iam not sure about the whole lengthening of the frame process, but i think if i did that i would put the motor mount in the middle and have a longer chain running to the live axle and the sprocket would obviously be in the middle as well, but thats just a little theory i had planed out in my head.But i'd be scared to lengthen the frame because it would cause a lot of weak spots in the frame it self and may just end up dogging out on me haha

You seem pretty knowledgeable about go karts so i have a few questions, is the governor on a 212cc predator engine adjustable and if so how ? And is putting a shifter on the kart just crazy and pointless ?

Thanks for all your help already i appreciate it

 

[jamyers]

Most of the reason we lengthened the frame was because we had the tools/materials and my nephew the engineer handy, lol. Didn't really *need* to, just made it easier at the moment. Now that I think on it, we wanted the engine in the center of the kart instead of one side, which meant the large axle sprocket needs clearance, which is why we added the extra length.

I'd think it'd be pretty straightforward to use the original engine mount, cut off the stub axles, and bolt a live axle under the stock location, keeping the sprocket, brake, etc in pretty much the same places as stock.

I'm no expert on Predators, I just picked one up. But I'm sure you can search this board and find a ton of stuff. My bet is that there's a governor spring that can be moved from one hole to another to give a different goverened rpm. Other than that, all I've heard about is removing it completely.

I'd think a shifter would be crazy difficult, although something like a Comet 30 Torque Converter would probably be a great idea.

Glad to help!

 

[Pocketrocket]

Yeah i might end up removing it completely but not just yet i want to see how it's going to perform w/o any thing being taken out of the engine.

I was out in my shop working on my kart today and i had an idea as far as the lengthening of the frame and i think this way i wouldn't loose much of the frames strength if any, it would kind of be like a swing arm with suspension. I'l have to draw up some plans but this way i would be able to mount the engine in the middle of the back end of the kart and that way i would have front and back suspension, and the kart won't shake me around if i hit a bump going 30mph or so.

As far as the shifter, i don't want a torque converter they are crazy expensive and the actual shifter with a few gears will be a plan for when the kart is complete and just want to experiment with it abit.

I'm really trying with this project to think of all the possibilities that i can explore with it. And in the end i'l have a kart nobody else has.

 

[jamyers]

...I'm really trying with this project to think of all the possibilities that i can explore with it. And in the end i'l have a kart nobody else has.

That's the spirit!!!

 

[Pocketrocket]

First substantial update

This weekend i wish i could have done more to my kart but i'm only human *sigh*, I finally finished sanding and priming the whole roll bar and all it's components came out with a really nice so i imagine once i go and get the paint i want the paint jobs gonna turn out nice. (Don't hold me to that, by no means am i an expert painter) I also discovered why i got the kart for so cheep, it has most likely been crashed into a tree at a high speed and the front wheel dehubbed because the square tubing that holds the spindle was bent back on one side causing you never being able to keep both wheels straight and hence why the wheels were so wonked. The front bumper is badly dented in as well so time to break out the welder and the cutting torch and see what i can do about that.(Photos of the damaged parts bellow) Over all getting the top end of the cart ready for painting was a huge win in it self.
I think i might have at most two more weeks in it to get it fully functional then i can start tweaking it.

Alright i'm off till next time... next week come at me
-Adam

 

[OzFab]

That should be easy enough to fix...

What I'm more concerned about is that it seems to have reverse ackermann; the steering arms are angled but, the wrong way...

 

[Pocketrocket]

Yeah my thoughts exactly but both steering arms are angled like that it must be the way thunder kart designed them, i'm not to familiar with thunder karts and theres not much info online about them so i just have to play it by ear.

 

[jamyers]

Heh, seems like running into trees is the thing to do with these karts - my daughter nearly tore the RF wheel off the kart awhile back. Good thing is, with a small welder and some scrap you can repair and reinforce a LOT on them...

On mine, the reverse ackermann isn't much of an issue - far bigger issue was the caster. Once we got some proper caster, it steers rather well on dirt / grass, although a lot of the time it's at opposite lock with the tail hanging out (whee!).

Like I said tho, the way go gain ackermann with forward-facing steering arms is to "cross" the tie rods at the steering column, with one bolting on top and the other bolting on bottom. That's my next project, I'll post pics.

BTW, nice crankshaft collection!

 

[Pocketrocket]

Haha thanks jamyers, there all pretty much useless at the time now but i like to look at them

 

[Pocketrocket]

Okay guys i found my self a gear box for my kart, it was on a old scooter that had a externally mounted gearbox. It is at one of my friends houses and he wants it out so i get the whole scooter at no cost. Might be worth a shot i think

 

[OzFab]

externally mounted gearbox.

This I wanna see; pics please?

 

[Pocketrocket]

This I wanna see; pics please?

I will upload pics as soon as i go to pick it up, i'm in no rush as it is to go pick it up right now because i want to run my kart w/o the gear box and then put it on to see whether or not it's going to give me better performance.

I think it will though, my reasoning behind the gearbox is that i've heard the a torque converter just gives you more low end (And it's so expensive!) So the idea of the gearbox it would be able to give me more low end and more high end at the same time. Plus who's ever seen a kart like that with a gearbox, I know for myself i haven't seen but one and that was more of a atv then a go kart.

Suggestions and comments are appreciated i'm all ears to any ideas. :arf:

Update* Didn't see much reason in bumping my thread with this small update, so i purchased a tiny tach today for the kart another 50 bucks i couldn't go wrong.

 

[Pocketrocket]

Update*

Hey guys
Progress has been slow because of work and other commitments, i did manage to get off my behind and bring my seat to my buddy who does upholstering, getting that back monday can't wait to see what that turns out like.
Needed some new wire disks for my grinder so on my way back i went to harbor freight and picked up a few. Got home and had about a hour to spare, between fiddling with other stuff I got this much done on the frame.

Got a free night tonight plus a long weekend so hopefully i will have everything the kart done by wednesday.

 

[landuse]

Looking good

 

[Regul8R]

That frame will do just fine~
My Predator 420 on same frame as yours. Live axle.

 

[Pocketrocket]

Nice! Looks brand new! Do they still make this kart? Cause i heard that thunderkart went out of business a long time ago.

 

[jamyers]

That frame will do just fine~
My Predator 420 on same frame as yours. Live axle.

Yow, electric start, CVT and all - I'll bet your kart really hauls! Nice work.