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JR's Cycle Car build


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Hey guys.


Some of you will have already seen this wee project in the Cycle car federation thread, I thought I should start its own build log as I was spamming the other thread with my dumb questions.

Please feel free to chime in and let me know if you think there is a better way that I could be doing something, any help is much appreciated.  



So, getting to the interesting stuff.... I want to build a mini version of this Austin Seven Special for my son.





Here is what I have done so far.





















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I messed up the Jackshaft, the RPM is not going to be enough for the centrifugal clutch to lock. I think I have a solution, I will elaborate another time.... Its late and its a long story.



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For everyone wondering why artyone is suggesting electric power, the reason is this. While the wee fella is young I want it to be simple to drive (a go and stop pedal). I can't get a centrifugal clutch with a low enough engagement rpm for my jackshaft to work. A few of ideas were floated, bare in mind he is only 2 so needs to be easy to drive.

1) Make it electric while he is young and use the engine as a generator.

2) Hook the clutch up to the brake pedal. Bro-tamatic spec.

3) hook the clutch up to the accelerator. As you give it gas the clutch releases.

At the moment I'm kind of leaning towards option number three just because I'm cheap and it won't cost any extra, should be drivable and because burn gas!


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Excuse my logic but I can't see number three being as simple in the reality of making it. Not that it isn't possible in some way but I just can't see it.


The clutch plates are held in and together by springs (clutch out) so to balance it in the out or apart (clutch in) position a stronger spring will be needed to hold that position. Then the action of pushing the pedal in... to get clutch out means either greater tension or compression of the spring depending on whether push or pull is used... okay, levers can fix that but longer levers mean greater travel. Imagine the handle bar clutch lever held in then tensioned there with a spring from some fixed point and now add a length of tubing to the lever then get the two year old in a chair and find the point where he can push the tube with his foot enough that the clutch will be out.


Am I wrong? What I can see is a two year old having to push a lever about 200mm... an 800mm lever.


I want to be wrong actually... it'd solve some engineering conundrums I've had for years.

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Artyone - the clutch for a cb125 is not at all going to be hard. Not like a big bike.

The gas pedal lever can have the pivot point mounted higher than the chassis rail to provide a mechanical advantage and make overcoming the spring tension quite easier.

As well as while the kid is only 4ft tall, a second gas pedal may need to be added for him to reach, and the linkage for this could also be set up to provide yet more mechanical advantage

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I should be able to rig it to have as little pedal resistance as I want. Fliboi is right, the force required to move the clutch is surprisingly little.





If I have a spring here that is only just strong enough to hold the clutch in and a weak return spring on the pedal it should work.


I still haven't decided what route to take yet. The scooter idea is a good one, I'll look into it.

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Okay... then I'm for option three too! It's quite neato really because if anything happens the foot will come off and the accelerator will spring back disengaging the clutch and it'll go into coast... and if it works really well you could almost put on an opposite brake too. Pedal out brake on.


Reminds me of when I tried to design a shifter to fit on an old holden three speed that would work like a motorcycle gear change... and am now kinda mulling over for the Suzuki carry sports thingy.

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Oh, flying brick... have you not seen the contour gauges? It's a band with loads of wires mounted perpendicular to the band and as you push it into a shape all the wires fit to whatever you push it into.


More commonly known as a profile gauge...or it's just cardboard and scissors when one forgets one has a contour gauge, for me anyways.

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