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Hi Paul,
The 9.7:1 rotors are considerably lighter than the
9.4:1 units. If you are going to use 9.7:1 units, then the best
option is to just get the whole rotating mass re-balanced. You can use the
eccentric shaft and both the counterweights you already have. It is always
better to start with counterweights that are too heavy, rather than try to
add weight to too light counterweights
The Balancier will first dynamically balance the
lighter rotor of the pair, and match balance both rotors to the same
weight. Then balance the whole rotating assy by just removing
material from the counterweights by drilling/grinding to get the balance
cortrect. This will give you a superbly smooth motor. .
WARNING: If you try swapping
counterweights, it's fraught with pitfalls, and you never really know
you have the correct counterweights until you run the engine (unless the assy
has been scrupulously kept together - the older shafts used to have
correspondence numbers stamped on the so you could tell if they had been
swapped). You will need both the front & rear Series V '89
-91 counter weights, which don't have any distinguishing part #s or
identification marks on them. A nightmare even if you are
experienced.
Re-balancing is ALWAYS the best option. What
it costs you to have the whole assembly dynamically balanced, you will
save some if not all by NOT buying or scrounging additional counter
weights. Additionally, you are guaranteed to have a perfectly smooth
engine. One has to experience a really good balance job to appreciate just
how smooth Mr Wankel's Wonderful Whirrler is! Factory motors, while
usually pretty good balance-wise, are balanced to a tolerance,
and are often not as smooth as they can be. Like I said, you have to
have experienced it to understand!! Take the time and the extra bux to do
it once and do it RIGHT!
Cheers,
Leon
----- Original Message -----
Sent: Tuesday, January 11, 2005 3:47
AM
Subject: [FlyRotary] 9.7 rotors
Hi, fellow rotorary enthusiasts....I need to ask
the group a question. I now have a street ported 4 port turbo engine,
into which I was going to put my 9.4 NA rotors and rotor housings. If I
pick up a set of 9.7 rotors, do I have to change anything else, ie concentric
shaft counterweight, etc, or can I just swap rotors? I have read that
you need the correct balance counterweight, but I assumed that is to balance
the concentric shaft, not the rotors? If I can just swap out rotors, and
it would have no effect on balance or anything else, I would go ahead with the
swap. Thanks in advance for all your replies. Paul Conner
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