HU baja

[loud1]

I'm talking about atv's, a friend of mine has a Can-Am 4 wheeler, it uses a fixed ratio torque converter to drive an automatic transmission. It is labeled as a cvt. So not all torque converters are cvt's.

So I should have been more clear as far as the transmission, it isn't a gearbox.

 

[Nick]

Here's another picture for you guys. This is the rear axle and gear box from last years. This years will hopefully be quite a bit different but this is what well fall back on if our big plans aren't as good as we think.

For this years the thought is a lighter (not sure how yet) gear box and hopefully a locking differential but we still need to do some research to see if making those changes will gain us much.

Oh I also included the logo I designed (on Forza motorsports 4) that my uncle is going to make into a vinyl for our cart!

 

[Nick]

This may be a really dumb question but... how hard is it to make the crank shaft run in the opposite direction? Is it as simple as reversing the pull start to spin it the other way or is there more to it than that? If we do change the rotation direction will it cause more wear and tear on the engine or anything like that?

Were thinking about reversing the rotation so that we can use a simpler and much lighter two gear gear box instead of needing an idler gear to correct the rotation. One option is to turn the engine 180* but then we would have to adjust the exhaust system which the rules are a bit picky on so if we can easily and legally change the engine rotation that would be great.

 

[itsid]

This may be a really dumb question but... how hard is it to make the crank shaft run in the opposite direction? Is it as simple as reversing the pull start to spin it the other way or is there more to it than that? If we do change the rotation direction will it cause more wear and tear on the engine or anything like that?

Depending on the engine
There's more I'm afraid.
I think you need a camshaft to alter the timing of the valves accordingly (that is a mirrored version of the original)
And of course a flywheel do get the ignition timing right.
I don't think you can buy off the shelf parts, so you have to make them yourself.
That is if you have a four stroke.

Some two strokes can simply run backwards (I'm not sure if all..)
just by altering the ignition system and pull start.

Were thinking about reversing the rotation so that we can use a simpler and much lighter two gear gear box instead of needing an idler gear to correct the rotation. One option is to turn the engine 180* but then we would have to adjust the exhaust system which the rules are a bit picky on so if we can easily and legally change the engine rotation that would be great.

Okay you lost me here.. you mounted the engine backwards, and don't want to correct that, but intend to alter the direction it runs?

'sid

 

[Nick]

Okay you lost me here.. you mounted the engine backwards, and don't want to correct that, but intend to alter the direction it runs?

Sorry probably wasn't too clear with all that. No we were considering turning the engine around so that we can use a two gear system instead of three but after talking to some of last years team that may not work since the output gear would have to be so much bigger than the input to get a good ratio.

Speaking of ratio what is a good ratio for a balance between torque and speed? The cart will weigh 300-380 lbs and will have a Briggs 10 hp engine, not sure on tire size or pretty much anything else yet so given that what are your suggestions? The current cart has a 11.4 ish ratio and from my research around here an 8 or 10 ratio seems to be the most common. The Baja cart needs a good torque/speed balance since there are competitions dealing with both.

 

[OzFab]

Unfortunately, for the most part, the only way to create the effect of a gearbox is to use a gearbox but, when you weigh up the options, you're only adding an expensive weight to avoid pushing it...

As you probably already know, 11.4 will give you great torque at low speeds but, not a huge top speed. I think you're on the money though, 8-10 is a good range...

 

[Nick]

I know I keep calling it a gear box but its only cause its literally a box with gears (current one is an input gear with a dual radius idler and an output gear) not the typical forward reverse etc gear box.

 

[OzFab]

So, what is its purpose; to create multiple ratios or more like a jackshaft?

 

[itsid]

So back to a series 40 Torque Converter as an option?
To have more torque at low speeds and a little more top speed.

'sid

 

[Desertduler]

Looks like a gear reduction box that would do the same thing as a jackshaft with three gears inline so the rotation of the axle is the same as the engine.

 

[Nick]

Looks like a gear reduction box that would do the same thing as a jackshaft with three gears inline so the rotation of the axle is the same as the engine.

This is how I should have said it! Thanks



Just a quick update. For the past week weve only been taking apart cleaning and reassembling last years cart. The design faze begins now. Looks like it is solid works time!

 

[Nick]

Preliminary design is beginning this week. Ill put up pictures of some of our mock ups as soon as I can but first where is the best place to get parts for the drive train? Well need gears, a CVT or torque converter and CV axles most of the other parts will most likely be made in house. I know I've seen a thread on here some where listing good places to find parts but I couldn't find it in my quick searching.

 

[souperman000]

Websites for Go Kart parts:

http://www.diygokarts.com/vb/showthread.php?t=1180

 

[Nick]

Thanks thats the one I was looking for

 

[Nick]

Haven't updated lately so here is whats new.

Weve decided on our tires. Were going with Maxxis Ravr XC 21x7-10 in the front and ITP Holeshot GNCC 20x10-9 in the rear. Were managing to loose roughly 10 pounds and shoulb be able to gain some speed and handling just with that.

I think were going to stick with the same CVT as last years since that is what we have test data on (we did acceleration and speed testing on last years last Thursday). It is a CVTech 0600-0021 driver and CVTech 5600-0171 driven. Id never heard of this brand and wasn't to sure about it but after finally finding a data sheet on it Im a little more confident.

Quick question to end this post. What kind of effects will mud and water (and heat) have on a CVT? Were required to have a cover on the CVT but were unsure on weather or not it will be beneficial to have vent holes in the cover or to leave it mostly water tight.

As always any answers or comments are appreciated!

 

[OzFab]

If there are slots or vents in the top of the cover, it will kill two birds with one stone; mud, water, shrapnel, etc won't get in & heat rises...

 

[Nick]

Here's an update for everyone the frame has been designed now it just needs to be tweaked here and there to fit the other subsystems correctly. We finished our CVT cover design. In the picture the darker fluid shaped part is carbon fiber (or fiber glass not quite sure which yet though) and the lighter parts are made of 6061 T6 Aluminum.

Does anyone know how the Briggs alternators (2, 10 or 20 amp) work? Are they just something you can bolt onto the fly wheel or is it more like in a car where it is belt driven? If anyone knows of a good tutorial video or walk through of some sort on how to install one that would be greatly appreciated.

 

[Nick]

Design deadline is Monday! Things are really starting to come together now. Were having a few issues in suspension design and weve decided that we needed to build our own rear knuckles but once those things are done (which should be soon) were good to go!

 

[Nick]

We need some internally splined bushings to fit the gearbox final drive gear to our CV joints and break any idea where we can get some? All the places I have found so far either don't make the size we need or the spline count we need. The one possibilty I might have found is an OH company that may wire EDM (if you dont know what this is I suggest looking it up cause it is really cool!) cut custom bushings for us but that could get expensive... So any supplier information would be great!

 

[itsid]

Hm without knowing spline count and size, and what you found already that doesn't fit your question is really tricky, don't you think?

'sid