Author Topic: Tacho ratio for Super Rocket  (Read 1381 times)

Offline orabanda

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Tacho ratio for Super Rocket
« on: 16.02. 2009 06:24 »
Hi learned BSAophiles,
Can someone please confirm what the ratio needs to be in a tacho to suit a 1960 Super rocket (tacho drive off oil pump, from front of inner timing case).
many thanks,
Richard

Offline beezalex

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Re: Tacho ratio for Super Rocket
« Reply #1 on: 16.02. 2009 16:24 »
Pretty sure it's 4:1.
Alex

Too many BSA's


Offline dpaddock

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Re: Tacho ratio for Super Rocket
« Reply #2 on: 16.02. 2009 21:08 »
You'll need a 2:1 CCW tacho. The magnetic Smiths part number on the dial will be RSM 3001/02A.
David
'57 Spitfire


Online trevinoz

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Re: Tacho ratio for Super Rocket
« Reply #3 on: 16.02. 2009 21:28 »
They are all wrong. It is 3:1.
Trev.

The tacho is a special as it is reverse to normal. Can't remember what is normal!

Offline flashblack

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Re: Tacho ratio for Super Rocket
« Reply #4 on: 16.02. 2009 21:35 »
I have to agree with trevinoz,i have that setup on my 1960 engine and the tacho has rc1303/03 written on it if that is any help *smiley4*
build it, ride it, live it!

Offline beezalex

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Re: Tacho ratio for Super Rocket
« Reply #5 on: 16.02. 2009 22:24 »
Yup,  What trev said.  I shoulda looked it up instead of working from memory. *red*
Alex

Too many BSA's


Offline dpaddock

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Re: Tacho ratio for Super Rocket
« Reply #6 on: 18.02. 2009 17:17 »
Ah, Alex, that's what comes from having "too many BSA's . . ."

Let's get to the truth, here, Richard. Detach the drive cable at the tacho, attach a small c-clamp to the cable end and rotate the engine forward one revolution. If you observe the amount of rotation of the c-clamp, you'll have the ratio - and also the direction of rotation which will tell you how the tacho needle will swing. Please let us know.
BTW - are you using a magnetic or a chrono?

     David

David
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Online trevinoz

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Re: Tacho ratio for Super Rocket
« Reply #7 on: 18.02. 2009 22:21 »
David, in the BSA 3:1 Chrono tacho, there is a gear set to reverse direction.. Trev.

Offline dpaddock

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Re: Tacho ratio for Super Rocket
« Reply #8 on: 19.02. 2009 23:07 »
I didn't know that, Trev; Thanks!
     David
David
'57 Spitfire