New Girl needs help with bike-kart!!!!

[lezli_15]

Hi all.

I'm hoping to build a 100hp kart by July 2009, but I've got a few questions before I crack on.

So far I have:

A Wright 125 chassis

Rear axle

Stubs

Wheels & tyres

...and a YZF 750



although it would be very straightforward to stick a small kart-engine on the frame - I just don't want to! ut:

I haven't done this before thou, so have some big concerns I could really do with some advice on:

1) how do I attach such a physically large engine? (I don't think I can weld chrome-moly at home) - I assume I will need an engineer to fabricate some form of subframe?

2) will it stop with a disk (or two) on the rear axle?

3) will I destroy the stub axles etc cornering at high speed with weight?

4) will the rear weight make it handle poorly?



Any advice would be really appreciated. I can't go ahead untill I know if it's do-able and affordable.


THANKS

 

[Sdannenberg3]

750? That seems pretty big! A lot of people oh here told me not to go above 250cc but hey, if hey if you got it then go for it! Heck, they put 1000cc gsxr engines on go karts! The thing that I would be really conserned about would be stopping. You might want dual disk brakes. Cause when your going 400mph then you need good brakes! But you should be fine with the frame. I'm just making my first kart from scratch and I am learning a lot as I go!

2) use hydraulic disk brakes on the rear axle.
3) the axle with be fine but Make sure the spindles on the front are hardened steel.
4) if you sit too far back and the engine is over the rear axle or too far back it will make you have understeer which is bad at any speed none the less at 80mph. I just got weights and set them where I wanted to mount my engine and had someone push the kart to test the steering.

 

[Kenny_McCormic]

I would not put a 750 on a stub axle cart. its suicide! Get ahold of a racing frame and go form there. Chromoly can be welded with oxy acetylene or TIG.

 

[modelengineer]

With that engine you really should have front discs as well as the rear one.

stub axle cart

I'm fairly sure she's talking about the front axles which are stub axles on pretty much all karts.

It will be hilariously overpowered and a nightmare to drive, I imagine.

 

[ed1380]

that would definitely be in the gixxercart category. when you make it can i have a ride?

you would definitely have to overengineer everything.

ive designed a kart before, never actually built it cause i dont have that kind of money. but what helped me the most was just looking at what other people have done. heres a good link i found http://www.motokarts.com/

 

[Kenny_McCormic]

How many busakarts exist? 1? I should get welding and make some $$$.

 

[lezli_15]

So I'm pretty much better off buying a kart engine then??

I want it to get around a mile long race track faster than my mates' cars and bikes, so it needs a pretty good balance of power and handling.

If I go straight on at every corner (or have to slow to a crawl) then all the power will be pointless.

I'm a bit gutted I hadn't realised there were 250 frames with provision for front brakes before I bought the one I've got.

Is there any way to fit front disks to a 125 frame? Or can I just put LOADS of disks on the rear axle? :-S

 

[Sdannenberg3]

Well adding more than 2 brakes on the rear axle would be pointless because its not about how many brakes, 2 disk brakes would be able to lock up the rear axle at 100mph no problem, but then you would just slide. Adding brakes to the front now will mean that all 4 tires are helping you stop, not just the back 2.

In reverse effect its kinda like a car. If you have 1000hp to the rear and you add another 1000 all to the rear you wouldnt be able to get that power to the ground. But now if you add that 1000hp to the front wheels, you have WAY more traction and you will notice it.

I do believe that you can mount front brakes onto the stub axles in front. You would just need to get longer spindles that have enough room for the brake and the wheel.

 

[2or3wheels]

yeah by adding front brakes to a cart not designed for front brakes you are adding alot of extra force to it. think about it its not really made to have that much force going into the spindles. just beef it up.

 

[Kenny_McCormic]

yeah by adding front brakes to a cart not designed for front brakes you are adding alot of extra force to it. think about it its not really made to have that much force going into the spindles. just beef it up.

Spindle arms and control arms can fold up.

 

[Sdannenberg3]

Spindle arms and control arms can fold up.

Ohh thats not so bad.... when your going 5mph! But ya, chances are if you need front brakes its because you are going 105mph and having ANYTHING to do with steering or brakes going out at high speeds could be very bad or very fun, it all depends on wether you end up in the hospital or not!

So its up to you, either spend time and $$$ on beefing it up yourself if you can do it, or spend more $$$ but less time and get a better frame designed for it. Its a trade off, for me I wanted to build me new kart all on my own cause its half the fun for me!

 

[Kenny_McCormic]

Ohh thats not so bad.... when your going 5mph! But ya, chances are if you need front brakes its because you are going 105mph and having ANYTHING to do with steering or brakes going out at high speeds could be very bad or very fun, it all depends on wether you end up in the hospital or not!

So its up to you, either spend time and $$$ on beefing it up yourself if you can do it, or spend more $$$ but less time and get a better frame designed for it. Its a trade off, for me I wanted to build me new kart all on my own cause its half the fun for me!

With such low ground clearance on most carts both wheels coming off at 50mph wont hurt anybody, just hit the brakes before you ram into something because you have no steering.

 

[lezli_15]

Thanks Sdannenberg3, I'd been a bit blonde there and failed to consider the limit of braking on just the rear wheels!!

The front wheels spin on their bearings on stub axles - so I guess the disks would have to be attached directly to the wheels? :-S

 

[Sdannenberg3]

Yeah, I think most bolt up on the inner side of the hub.(The side facing towards the inside of the kart)

Here is a picture I found of how they are set up on this kart.

 

[lezli_15]

Ah - see I have no front wheel hubs - my wheels run central bearings which sit directly on the stub axle. I think I can see me needing a very different set up to the one I have!

Thanks very much for the pic, thats fantastic.

I think I may be able to acheive that on my chassis with different wheels and stubs.

 

[hombre]

how you getting on with the kart lezli?

 

[ed1380]

a bit too late homes