honda gx 240 6-1 gear reduction kart

[mymumisaman]

hi im new so be gentle,

iv got my hands on a gx 240 engine for free (yay!) problem is its got a 6-1 gear reduction (boo). i dont like spending money so have decided to build a belt driven clutch system, so far the test went well with mk1 and im in the process of making mk2 (hopefully the last) , since im skint and dont like spending money im making it out of what i work with,...........furniture grade ply wood!.........its the best grade ply u can get! imported from finland lol so far iv managed to gear it so i get a 3-1 reduction, il have to post some pics.

but im curious.....has anyone tried making one out of ply before? is it doomed to fail? any opinions?

cheers for looking.

.paul.

 

[mckutzy]

Hi and welcome. Wooden karts are mostly frowned apon, due to there ability to disintergrate quickly without proper joinery and reinforcement.

What's your budget? Still going to need to spend about $100-200 for all the other bits.

 

[mymumisaman]

yeah i either have the other bits or i can make them, and im not planning to make a complete wooden kart that would just be silly, iv just made the belt clutch system from ply so i can make use of the engine, as to budget ........ if i cant find it then il make it, im only going to buy the parts that i cant make myself, like an axle, or bearings, so say my budget is about £100 or less.
once the belt drive is sorted im going to make a special hub that will allow the axle to drive both wheels, but will allow the wheels to spin faster than the axle when cornering ........if u get what i mean..........but like a diff but les complicated.

 

[mckutzy]

Unless you are incredibly talented in engineering or a real smooth talker, I say good luck on a $100(or equivalent currency).
Wood and metal typically dont work well with each other in mechanical mechanisms


Lets see your belt clutch system. post a pic.

 

[OzFab]

If you're asking what I think you're asking, I'll just say this: there is no wood on the planet that is good enough to use for high speed moving parts...

 

[itsid]

If you're asking what I think you're asking, I'll just say this: there is no wood on the planet that is good enough to use for high speed moving parts...

use cardboard instead

You can use wood (and by that I do mean wood, not glued scrap as in plywood) to make a frame.
If it's good enough for a Morgan +8 it'll be good enough for a kart,
but: it'll be alot heavier than an equally rigid frame made of steel.

Do not try to make any moving part out of wood especially not plywood.

'sid

 

[mymumisaman]

I'm not making a wooden frame cart,
Here is a pic ......if it works ...

 

[mymumisaman]

 

[mymumisaman]

its not quite finished and will be hardened with industrial grade epoxy, once setup properly. should do the job, and this isnt any run of the mill local hardware store ply wood! if i was to go and buy 1sheet 8ft by 4 ft by 1inch thick then im looking at a £340 bill! and thats at cost price
im not making a wooden cart, the frame and steering is going to be metal, its just going to be the belt drive, hubs and probably pedals made from ply, and as to high speed .........well it would b nice but its just a toy for the kids and maybe il have a go every now and then.

maybe il cast the parts in aluminium at a later date when i build the furnace again, but for now it should do the trick.

 

[mckutzy]

Overall it looks good put some work into it.
I do see a few thing I'd question.
Those belts will burn quicker than if you had used V belts. They have many points of contact to the "sheaves" along the face only(teeth). Since this is going to slip, those points are going to wear quickly. With the whole thing contained, there isnt good heat dissipation for the belt and sheaves.
Potentially as the wood heats and start to burn, it will loose it ability to grip the belt due to friction. Think of a fire drill(rubbing a pointed stick into another piece of wood to make an ember for fire), this I reckon will make a quick work of torching your "clutch"(belt tensioner).

If the sheaves were of a real good hardwood like a teak,oak at least or Lignum vitae/iron wood, there would be a better life to it and take a keyway better(I said better but no wood is good for this connection).


Also if a Vbelt would be used, it has three points of contact with out segmentation which will give good contact throughout the radii of the sheave.

Here is a good example of belt tensioner we keep referring back to on this forum. It is simple and to the point. It also is about the simplest way of doing things, Now given this example is welded it could be bolted together, But you did mention you are having a steel frame machine anyways so just incorporate this into it while your at it .
http://www.diygokarts.com/vb/showthread.php?t=2711


Also I would not recommend using ready rod(threded rod) for those axles, (I reckon this is just setup) they are weak and tend to break easily. Use a solid keyed axle and proper bearings, keys ect...

 

[mymumisaman]

some good points there, to be honest the one thing i didnt think of is the heat it will generate but let me go into further detail of how it works as its not quite the same as a belt drive,

the belt is 50mm wide as are the pullys, the wheel hub that pushes the belt is also 50mm wide, but its set up in such a way that when the wheel hub pushes the belt, it will lock between the 2 pullys (making contact) so the whole system acts like 3 cogs rather than a pully and belt system, the belt is there to provide grip to all 3 wheels and increase the contact area, and in theory shouldnt slip and create too much friction,

i agree that ply wood isnt the best material for this but i can use the parts iv made to cast it all in aluminium once im happy with it.

 

[mymumisaman]

also the engine has an inbuilt 6 to 1 gear reduction unit, so on tickover whilst the engine is spinning at say 1200rpm (its not but im just using it for example) the output shaft from the engine connected to the big pully is only spinning at 200 rpm, now iv made the smaller pully wheel half the size so it should change the reduction from a 6-1 to a 3-1 and be spinning at 400rpm, even if the engine is maxed out at 6000rpm the max rpm going off in the unit will be 2000.

 

[mckutzy]

Max rpm of that motor is governed at 3600 If im correct.

 

[mymumisaman]

iv taken the govenor off, other than that its a standard engine

my main concern would be the amount of torque and pressure going off in the system, so il do some static tests to see if it self destructs before making the mk3 lol

 

[Doc Sprocket]

While all of that is interesting, I totally fail to see the issue with the factory redux box. 6:1 is right in the ballpark for your average go kart, and the wet clutches those boxes tend to use are very stout and forgiving. So why all the extra work?

I gotta admit- the Ikea gearbox is interesting... LOL

 

[philip metzner]

First off let me compliment you on your woodworking skills. That is very nice work.
Is the gear box on your engine indeed clutched? All you need is a pulley on the engine and axle, and if the engine is not clutched you need a idler to tighten the belt. I built a kart like that a long time ago and it was very successful.

 

[mckutzy]

Looks like the first pic has a bicycle hub for an idler tensioner.

 

[OzFab]

the wet clutches those boxes tend to use are very stout and forgiving. So why all the extra work?

Hey, there's a good point, the redux box should have a built in clutch; just use similar sized sprockets on the gearbox & axle & you should be good to go

 

[mymumisaman]

No clutch on my engine I'm afraid, it's straight from an old cement mixer lol only had about 10 hours use from new

 

[mymumisaman]

Looks like the first pic has a bicycle hub for an idler tensioner.

It is. But it's not hollow