Author Topic: 200MPH Vintage Class Bike Build  (Read 77209 times)

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Offline astek

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Re: 200MPH Vintage Class Bike Build
« Reply #45 on: December 26, 2016, 06:54:26 PM »
May I ask the material specs for the frame?  I like the adjustment you've built into the rear end.   :cheers:

Thank you Frank, I'm using 1020 tubing 1"od - .120" wall

Offline sofadriver

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Re: 200MPH Vintage Class Bike Build
« Reply #46 on: December 26, 2016, 11:07:48 PM »
Frame not done yet.


Alp, I really like that weight distribution but how are you planning to keep all that chain under control?

Mind posting a pic from the top? I'm curious to see how narrow your knees will be.

Mike in Tacoma

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Offline astek

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Re: 200MPH Vintage Class Bike Build
« Reply #47 on: December 27, 2016, 01:08:47 AM »

Alp, I really like that weight distribution but how are you planning to keep all that chain under control?

Mind posting a pic from the top? I'm curious to see how narrow your knees will be.

I haven't built the seat pan yet, but it will be close to 20" wide. I will mount something below and top of the chain.

Frame detail:



Offline tauruck

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Re: 200MPH Vintage Class Bike Build
« Reply #48 on: December 27, 2016, 03:55:00 AM »
Great build and I'm subscribed 100%. :cheers: :cheers: :cheers: :cheers:
Good Skate Board wheels with the good bearings work!. :lol:

Offline JimL

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Re: 200MPH Vintage Class Bike Build
« Reply #49 on: December 27, 2016, 12:00:39 PM »
Hard to beat a good mountain-bike seat for a tight tuck.....those bike seats are shaped to let the legs position easily.  I used one on an APS bike in 2009 and it was perfect.

I ran sched40 PVC for a lower chain guide in the initial "feed out" area behind the countershaft.  Cut in half lengthwise, and you can heat and reshape the tubing by fanning it with a butane torch until it becomes pliable.  Work the shape with heavy gloves and then drop it in water to freeze the shape.  You want it flat in the middle and BOTH ends should be ramped away from the chain run to "smooth" the whip on the slack run.  I greased mine and it worked fine for all the years I ran that bike.  I had good luck with about 1/2-3/4" clearance over about 10" of run (as best I remember).  Anyway....It starts the chain running "calm" on its way to the rear sprocket.

On the top run, coming off the rear sprocket, I made a guide that will catch a broken or stretched chain and keep it feeding forward.  That gives you a chance of keeping the chain from partial wrapping the rear sprocket and piling up at the rear wheel.  Chains can break when they get hot enough to weld the pins into an arc, and then they dont go where you want.  Especially when you shift or lift.

JimL

Offline TheBaron

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Re: 200MPH Vintage Class Bike Build
« Reply #50 on: December 27, 2016, 12:55:11 PM »
Alp,

With such a long chain run,,, I'd use a "Ghost Sprocket" to keep things calm,,,,,

Look them up, It just might be the magic bullet you need....

Robert

Offline JimL

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Re: 200MPH Vintage Class Bike Build
« Reply #51 on: December 27, 2016, 08:24:18 PM »
Be careful about trying to control the chain whip at any distance from either sprocket.  As the chain runs through it's various ranges of speed, the peak amplitude of harmonics in the lash will move from one area of the length....to another.  Trying to catch that particular "falling knife" could be kind of like....trying to catch a falling knife! (humor... :roll:)

I have messed with rollers, idler sprockets, etc. in various applications. They can work good if you are willing to operate at a pretty much fixed speed.

That is why they completely disappeared in every manufacturers cam chain systems, many years ago (and were replaced by sliders).  I even had to ditch the idler sprocket and go to a shortened cam-chain type slide in my "replica 1915 Smith Motor Wheel" project...and that thing has very short runs (the entire engine, clutch, gear reduction, freewheel, sprocket sets....all fits inside a 20" bicycle rim). 

When we went to timing belts, we quickly learned that the tension and guide idlers had to be kept really close to load or direction change points.  Trying to work in the middle of a run broke all kinds of interesting stuff.

Simpler is better.  Just give the slack run a clean, smoothed exit and replace chains when in doubt.  You will not need more than about 10" of slider to let that chain get settled into the idea of heading for the rear wheel.

JimL

Offline astek

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Re: 200MPH Vintage Class Bike Build
« Reply #52 on: December 27, 2016, 10:28:08 PM »
Jim, I was thinking of a plastic pipe or a slider as well. Do you have a picture of your set up?

Robert, that ghost sprocket is interesting!

Offline thefrenchowl

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Re: 200MPH Vintage Class Bike Build
« Reply #53 on: December 28, 2016, 06:52:20 AM »
I'm hooked,

Thank you all for the insights and journey.

Maybe see some of you in 2017...

Patrick
Flat Head Forever

...What exactly are we trying to do here?...

Offline Sporty Dan

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Re: 200MPH Vintage Class Bike Build
« Reply #54 on: December 28, 2016, 10:36:24 AM »
This a thread that I will be watching! I like your frame layout. What are you using for a tubing bender? Those are nice clean bends, especially the 180 bend at the rear.

Offline WhizzbangK.C.

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Re: 200MPH Vintage Class Bike Build
« Reply #55 on: December 28, 2016, 01:38:36 PM »
This is how we dealt with a long chain run on Brian's XR500 rig. We built a metal box to contain the chain and support nylon guides that are contoured to help control chain whip, hopefully without adding too much drag. It's run every year (that racing has been viable) since '09 with no chain related issues cropping up. The metal screen allows visually checking the chain without taking anything apart and also provides some extra cooling air flow, in case that's needed. The chain doesn't even touch the nylon guides when adjusted cold, but the theory is that when it heats up and stretches the guides keep it from whipping too violently and keep the stresses down.



It's based on a similar design that we used on my TR25W in '08.



Of course, you're aiming for twice the speed we designed for, and it looks like you have almost twice the chain run, so some modifications may be in order to account for that.


« Last Edit: December 28, 2016, 01:40:26 PM by WhizzbangK.C. »
Ah, this is obviously some strange usage of the word 'safe' that I wasn't previously aware of.  Douglas Adams

Offline JimL

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Re: 200MPH Vintage Class Bike Build
« Reply #56 on: December 28, 2016, 03:01:55 PM »
Sorry, but I don't have pics anymore since a big computer crash.  I don't have the bike anymore, either.  I know that it is best to have any chain contact on a slider at a FLAT surface.  If you use a tube shape, the side of the chain will try to climb on contact and it starts whipping sideways.  That would be bad. 

Try messing about with some Schedule 40 PVC pipe and a butane torch.  The trick is to fan back and forth quickly, for a long time, and not close enough to turn the PVC brown.  Once it reaches softening point, it stays workable for a while.  The hardness of PVC is the real key, here, because the chain doesn't easily cut grooves into it.  The softer stuff like nylon and Teflon are slippery, but they don't like being pounded on.

Offline Seldom Seen Slim

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Re: 200MPH Vintage Class Bike Build
« Reply #57 on: December 28, 2016, 03:11:15 PM »
May I suggest that a heat gun might be a safer and more predictable way to work that plastic? :?
Jon E. Wennerberg
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Offline astek

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Re: 200MPH Vintage Class Bike Build
« Reply #58 on: December 29, 2016, 02:51:58 AM »
I'm hooked,

Thank you all for the insights and journey.

Maybe see some of you in 2017...

Patrick

Look forward to seeing you Patrick, thank you.

This is how we dealt with a long chain run on Brian's XR500 rig. We built a metal box to contain the chain and support nylon guides that are contoured to help control chain whip, hopefully without adding too much drag. It's run every year (that racing has been viable) since '09 with no chain related issues cropping up. The metal screen allows visually checking the chain without taking anything apart and also provides some extra cooling air flow, in case that's needed. The chain doesn't even touch the nylon guides when adjusted cold, but the theory is that when it heats up and stretches the guides keep it from whipping too violently and keep the stresses down.


thanks WhizzbangK.C.

This a thread that I will be watching! I like your frame layout. What are you using for a tubing bender? Those are nice clean bends, especially the 180 bend at the rear.

Sporty Dan , I use a manual rotary draw type bender for bends like the 180 in the back and I do freehand bends.

Thanks JimL, Seldom Seen Slim.
May I suggest that a heat gun might be a safer and more predictable way to work that plastic? :?
Sorry, but I don't have pics anymore since a big computer crash.  I don't have the bike anymore, either.  I know that it is best to have any chain contact on a slider at a FLAT surface.  If you use a tube shape, the side of the chain will try to climb on contact and it starts whipping sideways.  That would be bad. 

Try messing about with some Schedule 40 PVC pipe and a butane torch.  The trick is to fan back and forth quickly, for a long time, and not close enough to turn the PVC brown.  Once it reaches softening point, it stays workable for a while.  The hardness of PVC is the real key, here, because the chain doesn't easily cut grooves into it.  The softer stuff like nylon and Teflon are slippery, but they don't like being pounded on.

Offline wobblywalrus

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Re: 200MPH Vintage Class Bike Build
« Reply #59 on: December 29, 2016, 09:41:18 AM »
Some folks use an idler shaft with two sprockets and run two shorter loops of chain.  The rear sprockets ore offset to the outside to give clearance to run a wider rear tire than they could, otherwise.