The BSA A7-A10 Forum

Technical => Clutch, Primary, Gearbox => Topic started by: Rocket Racer on 15.03. 2011 07:35

Title: five and six speed boxes
Post by: Rocket Racer on 15.03. 2011 07:35
http://www.ttindustries.com/bsa_gearbox.html

what do I have to sell to finance one of these! *doh*
Title: Re: five and six speed boxes
Post by: muskrat on 15.03. 2011 12:47
Might have to find the wife a busier corner or sell the kids to slave traders. I have herd (not seen) of tri 5 speeds in BSA box.
5 might be OK but I think 6 is over the top. The problem with more gears is the motor never gets a rest. With a 4 the motor will drop down into the torque range before coming back on the cam. With a 6 it would always be on the boil, our old motors don't like that much.
I know a Red Hunter that performed quite well and reliable with a 4, but once fitted with a 5 blew up just about every meeting.
I ran a std box but had 3 crank and 3 rear wheel sprockets and geared 1st for 3/4 throttle in the slowest corner and made do with the rest. You could also play around with the box ratios, close the gap between 2nd & 3rd.
Cheers.
Title: Re: five and six speed boxes
Post by: Flatboy 1950 on 15.03. 2011 12:56
That guy Bruce Verdon , who makes these is an ex South African , living in New Zealand.
He used to lecture at Tech & had his own engineering business.
He had a Norton Commando hill climb bike that the 1000cc El Jappos could not touch !!!

Flatboy 1950
Title: Re: five and six speed boxes
Post by: Jim on 21.03. 2011 17:36
Or there is this possible alternative

http://www.novaracing.co.uk/bsa-gold-star-road.htm
Title: Re: five and six speed boxes
Post by: alanp on 21.03. 2011 19:27
I admit that I haven't checked the ratios on the TT Engineering box which Rocket Racer posted up but a year or so back when I checked the Nova box, I recall it had been designed was retaining the high RRT2 1st gear ratio and spreading the middle 3 ratios between that and the top gear. What I was interested in was a 5 speed box based on the 1st and top gear ratios of a standard box. I didn't want to get into the RRT2 situation again since I have to negotiate a lot of city traffic before the open road.
Has anyone gone into the TT box in more detail re. ratios? 
Title: Re: five and six speed boxes
Post by: Jim on 22.03. 2011 18:14
Nova Racing would appear to have made a more road friendly version as well as the racing one.

Ratio's as follows:
BSA 5 Speed Road                                % Drop             BSA RRT2                % Drop
1st        16 - 27   X  DR  =  2.482:1                                 1st    1.754:1
                                                               )    31.8%                                          )      24.4%
2nd       20 - 23   X  DR  =  1.692:1                                2nd   1.326:1
                                                               )    20.0%                                          )      17.1%
3rd        25 - 23   X  DR  =  1.353:1                                 3rd   1.099:1
                                                               )    13.9%                                          )        9.0%
4th        24 - 19   X  DR  =   1.165:1                                4th    1.000:1
                                                               )    14.2%     
5th        25 - 17   X  DR  =   1.000:1 
 
Drive Ratio (DR)  17 - 25   1.471:1
Overall Reduction 1st - 5th                    59.7%             Reduction 1st - 4th  43.0%
Title: Re: five and six speed boxes
Post by: alanp on 22.03. 2011 19:17
Thanks Jim, they must have had a lot of people asking about that ratio set up.
We've just today ordered a new driveway and windows etc from Everest, so the gearbox will have to wait.
Alan
Title: Re: five and six speed boxes
Post by: Jim on 23.03. 2011 17:49
Alan, what sort of twisted priorities are those? *eek*
Title: Re: five and six speed boxes
Post by: iansoady on 24.03. 2011 11:53
Thanks Jim, they must have had a lot of people asking about that ratio set up.
We've just today ordered a new driveway and windows etc from Everest, so the gearbox will have to wait.
Alan

If you'd ignored the "50% off if you order now" from Everest and gone for a local independent, you'd have saved enough for a six-speeder.....
Title: Re: five and six speed boxes
Post by: alanp on 24.03. 2011 12:45
I've had several others provide various windows, front door and garage door etc and their quality proved to be so poor over a 10 year period they're being ripped out and replaced by the best. I've ended up realising that you get what you pay for. When you have water sloshing around inside double glazed windows, water leaking through a buckled front door, a garage door that keeps falling down on your bikes, you know it's time to bite the bullet and pay up. Should have gone to them in the 1st place, it would have saved me money. It's a bit like some after market bike parts which are total c**p which you wish you hadn't bought but seemed a good idea at the time.
Maybe next year for the gearbox internals.
Title: Re: five and six speed boxes
Post by: Smithgd on 26.04. 2011 17:24
The 5 speed Alpha was designed by Steve Tonkin in the UK. You have to go thru him [so I was told by Alpha] to obtain the 5 speed gear box. The Triumph 5 speed converstion is being done in Calif. by Ron Halem. You can see him at Isle of Mann this year with his Green Gold Star [which will be racing with one of his 5 speed conversions]  GSR Racing
I have no financial interest, just passing on information.