Wordman's Build (with questions, answers, and suggestions)

What is the stock crank on the Triumph

like ours 360°

Correct, the stock Triumph crank is a 360°. The Triumph doesn't have the central bearing though, so it also has a crank "whip" factor (the crank flexes in the middle like a jumprope. Going with a 76° crank, while a lot more expensive for a Triumph, does even more to quell the vibration.
 
Correct, the stock Triumph crank is a 360°. The Triumph doesn't have the central bearing though, so it also has a crank "whip" factor (the crank flexes in the middle like a jumprope. Going with a 76° crank, while a lot more expensive for a Triumph, does even more to quell the vibration.

Interesting - I've never seen a 76° crank for a Triumph. That flexing of the crank was always seen as putting a limit on the revs. Does the offset crank allow a higher rev limit?
 
Interesting - I've never seen a 76° crank for a Triumph. That flexing of the crank was always seen as putting a limit on the revs. Does the offset crank allow a higher rev limit?

Triumph always had a pretty high rev limit, they just felt like they might come apart (and sometimes did) when you approached it. In racing, the offset "billet" crank would allow you to stay at the limit longer and with fewer chances of turning the thing into a grenade, I would think. As I am going with a stroker crank and a much larger bore (840cc), I plan on staying with 9:1 (at most) compression and fairly "soft" cams so I won't have to rev the snot out of it to hit the highway now and again. The whole exercise is to build a strong and reliable Triumph.
 
I'll be running a belt drive primary on the Triumph. I like the MAP belt drive, but the Bob Newby is my favorite.
008273_-_bob_newby_racing_-_belt_drive_and_clutch_for_triumph_unit_750_c.c._t140_tr7-1_720x.jpg


The only issue is, the Newby doesn't have a cush-drive (the cush is in the clutch assembly on a Triumph).

Well, XS650 tech to the rescue! Just received a nice TX500 rear hub and brake plate. The TX wheel is drilled exactly the same as the XS, so I can use the XS flanged aluminum wheel.

s-l1600 - 2020-10-28T142823.273.jpg

s-l1600.jpg


And since I already run an XS650 front wheel... Yes!
 
Interesting - I've never seen a 76° crank for a Triumph. That flexing of the crank was always seen as putting a limit on the revs. Does the offset crank allow a higher rev limit?

Hi Ray,
76º is the nearest the XS650 crankshaft splines will get you to the 90º offset that works best.
The offset reduces vibration which makes for a nicer ride.
 
Hi Ray,
76º is the nearest the XS650 crankshaft splines will get you to the 90º offset that works best.
The offset reduces vibration which makes for a nicer ride.

Actually, the XS is usually done a 277° (83°) offset because of the splines.

76° is what Phil Irving suggested for parallel twins (though this is based on rod length as well, and so is not definite).
 
Looking good Wordman - very nice indeed!

I am a little concerned though - in the second photo, it looks as though all of your little bits and pieces will fall out of that vertical drawer....;)

All seriousness aside - is that Mr. Mulligan R/C model on the hoist?

Pete
 
I like the way you roll! Nicely organized tool box. :geek: What is that structure in your garage? On overhead crane or a car hoist? Or.......:umm:
 
I like the way you roll! Nicely organized tool box. :geek: What is that structure in your garage? On overhead crane or a car hoist? Or.......:umm:

I'd say that is a four-post hoist and its in a pretty big@ss garage too.
 
Looking good Wordman - very nice indeed!

I am a little concerned though - in the second photo, it looks as though all of your little bits and pieces will fall out of that vertical drawer....;)

All seriousness aside - is that Mr. Mulligan R/C model on the hoist?

Pete

I don't know what the brand is. It was my dad's, but he can't fly it because of his neck (looking up triggers a headache and puking). I have everything, I just haven't had a chance to sort it all out and go flying.
 
I don't know what the brand is. It was my dad's, but he can't fly it because of his neck (looking up triggers a headache and puking). I have everything, I just haven't had a chance to sort it all out and go flying.

The Mr. Mulligan was a 1930s racing plane. The official designation was the Howard DGA-6 (DGA stood for Damned Good Airplane...). Only one was built and it crashed during a race in the 1930s but several replicas have since been constructed.
300px-Howard_DGA-6_Replica.jpg
 
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