Gearing problems

[Farmingstock]

Hello all

First post and hopefully I’ve come to the right plac,

I have built my son an off road kart/buggy.

The kart has a 6.5 clone engine, a gear ratio of 6-1 and 18” tyres.

On flat ground or on the road the kart moves ok, but as soon as it’s on grass or hills it won’t budge.

I think I am going to have to change all the sprockets and create a jack shaft but I’m wondering about things like chain tension and alignment?? Is there a thread on how to build one from scratch?? Also would a torque converter be a better option??

Thanks for any help

 

[Kartorbust]

Depending on the weight of the kart, you might want to be at around 7:1 or lower. Here's an example with a back plate, which are not always needed. You'll lose your top end, but out of the hole it'll be a lot veterans should be able to get you uphill a lot easier.

 

[Farmingstock]

Thanks for the reply

Are they available to buy?? The kart isn’t that heavy it’s not that big and is for my son more than me, I think it needs to be more like 9/10-1, I’m not that bothered about top speed just want him to be able to go on the grass/hills etc.

 

[anickode]

If you buy a $60 Chinese TAV2 on eBay and bolt it on, it would likely solve all your problems and be cheaper than messing with additional jackshafts (which might be necessary so your axle sprocket doesn't hit the ground) and different sprockets.

Take the clutch off, put the TAV on, and drive it away.

You can then adjust the governor (or pedal travel) to limit the top speed if you see fit, since torque converters do not suffer the same damage as centrifugal clutches from running at partial throttle for extended periods of time.

 

[bob58o]

Torque Converter will get you moving.

https://www.ebay.com/itm/Go-Kart-To...m=273067380107&_trksid=p2385738.c100677.m4598

 

[Farmingstock]

I thought about a torque converter, do they higher the ratio at first then lower when you get going??

Cheers

 

[bob58o]

I thought about a torque converter, do they higher the ratio at first then lower when you get going??

Cheers

With the standard 6" driven pulley...
2.68 :1 in low.
0.90 :1 in high.

 

[Farmingstock]

Ahh so that translates onto the main drive?

So say the main drive is for example 5-1

That will make the kart 13-1 at low revs and 5-1 ish at high revs??

Is this about right??

Thanks again

 

[Kartorbust]

You get a 10% over drive with the 6" driven, so at 5:1 in the top end you are really about 4.5:1.

 

[Farmingstock]

And what would it be at low end?? As I will be changing the chain linkage to 428, so will may change gear ratio too??

 

[Kartorbust]

In low you'll be about 13.6:1 with a 5:1 ratio.

 

[anickode]

And what would it be at low end?? As I will be changing the chain linkage to 428, so will may change gear ratio too??

Particular reason for this?

I can't remember for sure, but I don't think 428 chain is compatible with 40/41/420 sprockets... And it could be a PITA to find a 428 sprocket for the TAV.

The TAV kits usually come with a 12t #35 and a 10t #41 (which will work with 40/41/420 chain).

Odds are your kart already has a 35 or 41 sprocket... Why change it?

 

[bob58o]

Yep.
6:1 becomes 6 x 2.68 = 16.08 :1 when you start from a stop or anytime you need it.
6:1 becomes 6 x 0.90 = 5.4 :1. Once you get moving, the TC will auto shift into high gear.
If cruising along and come to a hill, the TC will automatically downshift to give you the gearing you need for the hill.

The kit will come with a 10T #41 sprocket, 12T #35 sprocket, or both.
#420 chain will work with the #41 sprocket and is pretty strong. I don't know jack about #428 chain. Guessing it is similar to the strength of #420.

Most 30 series torque converter kits have a 5/8" jackshaft. You would need a 5/8" bore, "C" type sprocket, #428 pitch and with how ever many teeth you want if you want to use 428 chain. I don't think those exist.

420NZ Pin Length 16.65mm, Roller Dia. 7.77mm, Plate thickness 1.8mm

428NZ Pin legth 18.90mm, Roller Dia. 8.50mm, Plate thickness 2.0mm
http://dirtrider.net/forums3/threads/whats-the-difference-between-a-420-and-a-428-chain.94185/

 

[Farmingstock]

Particular reason for this?

I can't remember for sure, but I don't think 428 chain is compatible with 40/41/420 sprockets... And it could be a PITA to find a 428 sprocket for the TAV.

The TAV kits usually come with a 12t #35 and a 10t #41 (which will work with 40/41/420 chain).

Odds are your kart already has a 35 or 41 sprocket... Why change it?

It’s homemade and I got the engine off a kart so currently got a 219 pitch chain on unfortunately, so definitely going to need changing.

 

[Kartorbust]

You're in the UK or at least Europe correct?

 

[Farmingstock]

Yeah based in the UK northwest

 

[Kartorbust]

I'm not sure how much shipping will cost for you, but there's a company in California, Azusa Parts. They have quite a list of sprockets, from #219 up to #630. http://azusaparts.com/product-category/sprockets/