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Old 09-06-2010, 10:54 PM
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Default DIY 2-speed Gearbox.

Following on from my intro thread, I thought Id post this here for those who don't trawl the intros section.

I've just completed a 2-speed box for my Drift-II kart.

There's a build rundown on my site:
www.thepixelpump.com

It prettymuch covers all the issues I ran into. So, for anyone thinking about adding an extra gear to a single speed kart this might help.

Cheers.

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Old 09-07-2010, 02:33 AM
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Wow this is amazing! How much did it cost to build?
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Old 09-07-2010, 02:36 AM
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Had a look at your website. You have made some awesome creations. Its cool to have another Perthian on here. I think there's only about 5 of us on here.
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Old 09-07-2010, 02:39 AM
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Quote:
Originally Posted by EagleTalons View Post
Wow this is amazing! How much did it cost to build?
Quote:
I chose this design because it's relatively uncomplicated and cheap, the total cost was a little under AUD$350
Straight from the website. In today's current market 350AUD is 319.72500 U.S. dollars.
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Old 09-07-2010, 05:12 AM
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Yeah, about AUD$350 in parts. A bit extra for some tools and consumables (welding rods etc).

In the end its only slightly cheaper than a TAV2 (AUD$380ish), but more fun to build and I get to have a shifter. TAV would also need a jackshaft so that'll add $50+ to that option.

Thanks for the kind words guys. Hope you find the info useful.
I havn't gone into great detail, but there should be enough for someone with basic mech' skills to get something working out of it.
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Old 09-07-2010, 05:45 AM
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wow stupidly simple
amazingly awsome

im definatly useing this on a kart someday
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Old 09-07-2010, 05:49 AM
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Brilliant design! I think I might copy that for mine, with a few revisions of course . Very clever design, thanks for documenting and posting this!

Good to see more West Australians on the forum too.

Thanks

Hayden
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Old 09-07-2010, 02:13 PM
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320 bucks seams like alot to me. is that 320 including buying tools like welder, chop saw, ect? a while back i though of using hubs with bolts like that, but once again didn't have money/time its nice to see some one make one though, . you should totally make it into a 4 speed, lol
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Old 09-07-2010, 06:21 PM
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Maybe I'm what you'd call stupid but, without doing too much reading, this is flying over my head.
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Old 09-07-2010, 06:37 PM
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Quote:
Originally Posted by redsox985 View Post
Maybe I'm what you'd call stupid but, without doing too much reading, this is flying over my head.
its not really complicated at-all he basically uses a cent clutch instead of a manual clutch (which prob bogs down performance but still works) then in stead of using gears and conventional syncromesh he uses sprockets with bolts through them and a sliding hub (which acts as a more low-key syncromesh. with holes in it which locks into the bolts on the sprocket. other than those slight modifications it works in basically the same way as a conventional manual car transmission.

p.s. i know this sounds silly but i find this book to be this a good resource for finding out the way things work (hence the name, lol)
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Old 09-07-2010, 08:24 PM
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this was my favouite book as a kid
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Old 09-07-2010, 09:24 PM
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niiiice !

i thought of a similar desing a while back but backed out because i tought it would engage too harshly... btw how is the engagement?
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Old 09-08-2010, 01:29 AM
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I took it out today for another test run. 2 hours of solid dirt-karting and no mechanical issues apart from one of my shifter cables slipping tiny bit, fixed with half a turn on the adjuster.

I ran a circuit shifting up and down gears and while the box does require a bit of mothering it engages fairly easily (most of the time, 4 out of 5 times). You definitely have to lay off the throttle when shifting though. The way I have it worked is you have to take your hand of the throttle lever to shift anyway, but shifting with revs results in quite a bit of clash on the dog clutch. Sometimes the clutch just doesn't want to engage and you end up coming to a stop before you can get it to shift into gear, this is a bit of a pain and means you have to plan your shifts a bit more.

I think in v2.0 I would concentrate more on the dog/clutch geometry the stud and hole system is pretty unforgiving when the whole lot is spinning. Something with a tapered edged teeth would probably work more reliably, but would a tapered tooth also try to disengage when coasting, or worse partly engage while spinning rapidly and spit teeth all over the back of my head?

There are a number of off-the-shelf dog-clutch mechanism designs that might be worth using as inspiration...



@r97: Its about AUD$350 for the; sprockets x6, 3/4" shafts x2, bearings x4, chains x10foot length, and square tube 4', 1/4" plate, bolts, keysteel and to have the 20x50mm clutch boss turned. All the bits I couldn't make myself.
So yeah, not as cheap as using a free motorcycle engine like I have on my previous Karts.

I hope you guys can improve on my design and come up with better designs.

Last edited by Wim; 09-08-2010 at 01:43 AM. Reason: more and better
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Old 09-08-2010, 05:16 PM
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a manual clutch (or belt tensioner, but a manual clutch is better) would defiantly improve performance, also making it so that your "synchromesh" has a sort of friction plate that contacts the sprocket and brings them to the same speed would fix the problem, but that makes things wayyy more complicated, like this.

adding more bolts on the sprocket and more holes in the syncro ("clutch" as labeled on your website)would also help, drilling out the holes on the syncro to a bit larger size could also improve things.
p.s. if i ever get the $$ i may build one of these.
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Old 09-08-2010, 07:28 PM
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That type of gearbox you have designed has no syncro, but it is constant mesh. Very ingenious, well done.

Cheers for that image R97, I never understood quite how syncro worked mechanically until now.
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Old 09-09-2010, 06:55 AM
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@r97, I did think of some sort of synchro to bring the two moving parts up to speed but couldnt come up with anything compact and build-able enough. I had in mind something like a large wave-spring washer with shallow dimples in the plates for it to grip into - not too much friction to cause shock but enough to sync' the moving parts. I may still add this.

The holes in the clutch plates are 10mm and the bolts are 8mm, this gives a bit of freeplay. I might add a bit of taper (countersink) to the holes or drill the holes out to 12mm and see if that improves engaging.

Thanks again guys for the input.
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Old 09-09-2010, 07:35 AM
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I wouldn't drill the holes out to 12mm that would create play in the gearbox. A taper sounds like a good thing to try.
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Old 09-09-2010, 12:41 PM
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from what i've seen, engagement would be eased by knocking the corners off your dogs. chamfering if you will. if you haven't already. nice setup, but wouldn't it last longer in an oil bath or at least a sealed box?
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Old 09-09-2010, 04:44 PM
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i have an idea in the works for a syncro, but the easiest thing is to do what mike said, but syncro will improve things alot, also consider drilling more holes, and maybe putting in more dogs, so that it locks in faster with less wear.
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Old 09-09-2010, 07:35 PM
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i think i would put larger holes for the dogs to slip into. putting more holes in it will weaken the metal.
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