2.5L Rocket Stroker Engine Kit with 6 Speed Transmission (R&D)

SDR_11 Rocket said:

Thank you. I will also contact Robinson Industries. I did find they still have the Billett 4th gear listed. Not to rehash everything but I saw a cursory reference in which you commented I believe regarding the option to modify the final drive ratio to suit this purpose in a simpler fashion. Is that just not workeable or is it not productive in terms of ratio gain ?
To be very clear if the reference file / image does not state "modify existing" then the entire component needs to be manufactured. ?
The machine shop said they would go over the CAD files and provide a quote at no cost. They asked what quantity for initial parts quality and testing I told them 1 each as far as I know ( please clarify ) but I was also thinking 2 in case it would be advisable to have parties on both continents test at the same time.

Click to expand...

When you say final drive, do you mean the output shaft to torsional damper?
The final drive is the thing on the left side of the rear wheel.
The torsional damper sounds simpler and less trouble than adding a 6th gear, but when you get into it, it becomes apparent that it's probably a similar amount of trouble and expense.
The primary reason why I steered away from the output shaft / torsional damper gears is because you cannot change the centres, and the degree of difficulty in changing the gears to something of the right ratio and having the exact correct centres is quite high.
The simplest solution would be flipping the ratio (e.g. 46T & 48T to 48T & 46T) but this didn't yield much of a rev drop vs what a 6th gear would do iirc, or at least not enough to warrant all the work and expense.
Plus they are helical cut gears and the rest of the cogs are a lot of work to make.

Don't get me wrong, it can be done, but I'd definitely prefer the 6th gear.


Re the 'modify existing' question, yes.

R-III-R Turbo said:

When you say final drive, do you mean the output shaft to torsional damper?
The final drive is the thing on the left side of the rear wheel.
The torsional damper sounds simpler and less trouble than adding a 6th gear, but when you get into it, it becomes apparent that it's probably a similar amount of trouble and expense.
The primary reason why I steered away from the output shaft / torsional damper gears is because you cannot change the centres, and the degree of difficulty in changing the gears to something of the right ratio and having the exact correct centres is quite high.
The simplest solution would be flipping the ratio (e.g. 46T & 48T to 48T & 46T) but this didn't yield much of a rev drop vs what a 6th gear would do iirc, or at least not enough to warrant all the work and expense.
Plus they are helical cut gears and the rest of the cogs are a lot of work to make.

Don't get me wrong, it can be done, but I'd definitely prefer the 6th gear.


Re the 'modify existing' question, yes.

Click to expand...

As it applies to the output shaft / torsion damper consideration. Understood.
I will be in touch when I hear back from the machine shop. It was a positive discussion in principal. For the purposes of figuring he asked if I was inquiring for a one off build ( which he was very open to ) of the parts and as I do not know what level of interest there is I communicated that there is likely sufficient demand for at least a modest run of parts. He also had immediately stated that he realized that the very first parts would be evaluated and trialed for accuracy before doing a run. Which though it stands to reason I felt that it was energetically a good starting point in that he was not associating his willingness to accomplish the production on the size of the order. I do feel that I am placing the cart before the horse in getting into this level of detail before any cost structure is established but thought it worth conveying the energy of the encounter.

Since you did not clarify... I am assuming one of each component is sufficient for one transmission build

I need to make sure the parts that are to be modified are still available from Triumph. I will look through your files to see if the part numbers are present and if not I will look them up. I do have a very friendly parts guy at a dealership a couple hours away that used to drag race a supercharged versions of this bike and he has been more than helpful in determining availability of parts