Shifter Kart...sort of.

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REAR
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Joined: Sat Jun 16, 2007 10:19 am

Shifter Kart...sort of.

Post by REAR » Wed Feb 07, 2018 10:23 am

Received a call from fellow REAR engine karting enthusiast Mike Schagler from Buffalo New York the other day and Mike went on to tell me of a 2-speed driveline concept he was working on.

Mike's 2 speed concept is really nothing new since 2 speed minibikes have been around since the 60's but the idea is well worth taking a look at. Another cool aspect of Mikes set-up is he has been able to assemble it with 'true' vintage parts from the 60's also.

What Mike did was he took a Mc-91 and bolted it onto a Palmini jackshaft mount then installed a motor clutch with 2 sprockets to drive a one way sprocket and a clutch on the jackshaft with a sprocket then going to the final drive at the rear wheel.

Currently the set-up is still in the testing stages with different engagement speeds on the clutches and ratios being tested but the results look promising with the initial set up featuring a 12:1 first ratio shifting into a 6:1 final ratio.

Only some time and some tuning will tell if the set-up is viable but no matter what its a very interesting concept and set upas the pictures below will show.

Image

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R.E.A.R.

Mike Anderson
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Re: Shifter Kart...sort of.

Post by Mike Anderson » Wed Feb 07, 2018 1:07 pm

Pretty cool, leave it to Mike for a neat design. By the way how was the swapmeet? I couldn't make it this year.
Later Mike

ted johnson
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Re: Shifter Kart...sort of.

Post by ted johnson » Wed Feb 07, 2018 7:21 pm

Pretty cool concept and execution, but DEFINITELY not vintage! TJ

REAR
Posts: 686
Joined: Sat Jun 16, 2007 10:19 am

Re: Shifter Kart...sort of.

Post by REAR » Thu Feb 08, 2018 6:02 am

Teddy,

I don't know if I would go so far as to say "not vintage". Mike's setup is completely assembled with parts from the 60's with no machine work required so it was within reach of the average Joe to assemble and don't forget that karters used to be able to build what they wanted so I wouldn't be surprised if someone was out trying a set up like this in a dark alley somewhere.

Personally, those small chains lengths look to be the weak link in the set-up along with excessive crank stress.

Here is a better explanation of how the set works. This explanation is copied from a outside indviduals description and not from R.E.A.R.

The clutch on the engine out put has 2 sprockets on it instead of just one, the first chain goes from the engine clutch to the large sprocket on the jack-shaft, this large sprocket has a built-in free-wheel device [sprag]. the second gear is setup in a way so that the second chain coming from the engine clutch goes to a sprocket welded to the shoe assembly on the jack-shaft (not the drum like in a normal cent clutch) the shoe assemble on the jack shaft is also on bearings and has more spring tension so that it only engages when the jack-shaft is spinning near its max rpm, the jack-shaft clutch shoes expand and lock onto a drum fixed to the jack shaft, now the second gear is engaged, second gear spins faster than 1st so the free-wheel releases ands spins freely on the jack shaft. at the other end of the jack shaft is another sprocket which simply runs to the wheel. so engine cent clutch engages spinning both 1st and 2nd gear chains, first gear chain (roughly a 2 to 1 ratio) moves the free-wheel sprocket on the jack shaft faster than the shaft thus engaging the free-wheel and 1st gear along with it. next the engine revs to higher rpm which engages the second gear clutch which grabs onto a drum that is fixed to the jack-shaft(the heavier springs in this clutch make it engage only at high rpm), the second gear has a roughly 1 to 1 ratio so the jack shaft is now going to spin faster than the 1st gear free-wheel sprocket, when this happens it dis-engages the free-wheel. if you really wanted to you could install a free-wheel on the jack-shaft clutch drum and put on another.

R.E.A.R.

ted johnson
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Re: Shifter Kart...sort of.

Post by ted johnson » Thu Feb 08, 2018 10:09 am

Guys, I wasn't referring to the idea of innovating a new setup for which parts and general mechanical knowledge was available in 1962 or thereabouts. Heck, you know me, I have no qualms about building something new or different. I was referring to the IKF rules that stated something to the effect that no change of gears is permitted while the kart is in motion. That rule was there from the beginning. I am not saying the device isn't cool, just that it would not have met the vintage rules. Even a V-12 manifold isn't vintage, but it meets the vintage rule book. Ted

jim fair
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Re: Shifter Kart...sort of.

Post by jim fair » Thu Feb 08, 2018 1:27 pm

Ted I still have the V-12 and 250 Tillotson carbs I got new in 1968 so wouldn't that make it true vintage . Jim

Rob Voska
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Re: Shifter Kart...sort of.

Post by Rob Voska » Fri Feb 09, 2018 7:21 am

While not standard on karts because of the fixed gear ratio rules two speed minibikes have been around for a long time. I've ridden a few & there is a transition period that is odd but I'm sure it would be less odd if I were a 75 lb kid!

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