T140 crank balance factors

kommando said:
I have the info somewhere but it's of no use as he no longer operates independently.

Found it, he moved to

J&J Engineering
Unit 5
Unicorn Business Centre
Chiseldon
Swindon
SN4 0HT

But left there too, no idea where he went too.
Click to expand...

OK, thanks.
 
acotrel said:
The balance factor depends on the RPM you use the most. For continually revving above 5,000 RPM, I would use the 80% balance factor. For commuting I would use standard.
Click to expand...

I honestly wonder how reliable such rules of thumb are. I've come across similar advice before, ie: higher revs = higher balance factor. I have a feeling there's a lot more to it than that. The TSS was an engine designed to rev far higher than the T140, yet Triumph deemed it prudent to reduce the balance factor from 74% to 69%.
 
Tigernut said:
I honestly wonder how reliable such rules of thumb are.
Click to expand...

Its not, static balance is set by fitting the engine into the intended frame and trying it out, its subjective as it depends partially on the rider and his riding style but also the resonate frequencies of the frame and its attachments. Changing the static balance factor changes the direction the out of balance weight is directed, revs changes the amplitude of the out of balance force.

 
kommando said:
Its not, static balance is set by fitting the engine into the intended frame and trying it out, its subjective as it depends partially on the rider and his riding style but also the resonate frequencies of the frame and its attachments. Changing the static balance factor changes the direction the out of balance weight is directed, revs changes the amplitude of the out of balance force.

Click to expand...

Thanks for the link, but this kind of mathematical stuff is way over my head! Using nothing other than a gut feeling that Triumph will have known what they were ding when deciding on the optimum balance factor to us for the TSS crank, I feel that there can be no harm in following that. The crank will need re-balancing because it will have non-standard rods (Thunder Engineering) and non-standard (for the crank & rods) pistons, ie: original T140 pistons, rings & gudgeon pins.

I am asking for a 69% balance factor if this is easy to achieve, with up to 74% if that makes it easier without having to remove too much metal.

My feeling (again, this is the best I can go by with my limited comprehension of the physics) is that, with a good crank, dynamically balanced by experts (the people Steve Campbell uses so they must be good), it should run smoothly.

I'll report back on here either way, when I have the bike running - though I very much doubt this will be before next spring.
 

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