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Old 04-10-2010, 12:32 PM   #21
worn
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Default Re: 180 Degree Crank

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Originally Posted by Dragon View Post
Re -




Read > http://www.offsetcrank.com/thefirst.htm

then click back to "home" and look around...
I have been friends with Geoff at Ed G Cranks for over 30 years and have followed his development of his offset crank conversions and have owned a Triumph with his conversion. The Triumph in my avatar is a '67 Bonneville that was the 2nd conversion done by Ed G Cranks. I can honestly say that it is faster and smoother than any stock 650 or 750 Triumph. There is still vibration but no buzzing or tingling and the bike does not wear you out riding it like a stocker can. Parts didn't vibrate loose either. The lighter flywheel and rods, the firing pulses, it just accelerates harder with much better throttle response.
If you ever get a chance to ride a Brit twin with an offset crank done right, you'll get the picture.
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Old 04-10-2010, 01:53 PM   #22
gearhead1951
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Default Re: 180 Degree Crank

there is a thread on this subject at www.britbike.com , John Healy gives similar comments as Worn and if you can get in touch with him Dave Nourish will tell you that th' 90 degree crank is th' mutts nuts fer a street machine !!
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Old 04-10-2010, 03:15 PM   #23
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Default Re: 180 Degree Crank

now someones answering what i asked
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Old 04-22-2010, 08:39 AM   #24
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Default has anyone ran a 180 crank in a unit triumph?

I recently got my hands on a Pazon smart fire ignition for a 180 crank and was wondering what some of the pros and cons were to swapping the 360 out for a 180. Or, if anyone had any luck manipulating the 180 ignition to work on a 360 crank.
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Old 04-22-2010, 09:56 AM   #25
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Default Re: has anyone ran a 180 crank in a unit triumph?

http://www.jockeyjournal.com/forum/s...ight=180+crank
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Old 04-22-2010, 01:30 PM   #26
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Default Re: 180 Degree Crank

At one point a few years ago I got my hands on a book that gives the formulas for calculating the primary and secondary shaking forces on an engine. I spent a little time inputting it all in to a spreadsheet and graphed the results for a parallel, 180 and 90 degree twin (yeah, I'm a nerd).

One thing that gets introduced when you go from parallel to 180 or 90 is a rocking couple. When the pistons are offset one is going up while another is going down so they introduce a twist in the vertical plane going front to back through the engine. So, that gets added where it didn't exist previoulsy. The couple is highest for the 180. So, either one of those is going to add a new and different kind of vibration than was there with the parallel setup.

Just from a graphic perspective, the 90 did seem the best, primary and secondary shake is significantly reduced over the parallel and the rocking couple is less than the 180. Naturally this was theoretical but it seems that the experiences of others supports it.

By the way, th H*@da CB360 was a 180 degree twin. Supposedly it revved much higher than its CB350 parallel twin counterpart.
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Old 04-22-2010, 01:41 PM   #27
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Default Re: 180 Degree Crank

^ good effort.
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Old 04-22-2010, 05:23 PM   #28
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Default Re: 180 Degree Crank

Aside from the benefits already mentioned, where the 90 crank would have really helped would have been in dirt track racing, as it would have given the Triumphs, BSAs and Nortons similar traction characteristics to the Harleys. The unequal firing order of the V-Twin (or the 90 crank in a parallel twin) keeps the tire hooked up better on dirt. Many of today's MotoGP and WSB bikes use irregular firing orders for the same reason.
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Old 04-22-2010, 09:17 PM   #29
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Default Re: 180 Degree Crank

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^ good effort.

Thanks, that really makes me feel good about spending all that time in engineering school.
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Old 02-08-2011, 07:55 AM   #30
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Default Re: 180 Degree Crank

I stumbled across this last night. It's writeen by ViWilloughby and it is a discussion on balance that was proposed by Phil Irving for the British twins.

http://www.xs650.org.au/smoothness.htm
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