930 shift linkage ratio/leverage question

[Terry Oxandale]

For you guys using the 930 or G50, what is your shifter handle ratio? I'm fabricating the shifter mechanism, and am planning on a 2:1 ratio at the handle. In other words, the 930 shift rod moves about 22mm from neutral to each gear (or about 44mm from 1st to 2nd), but I'm designing the mechanism so that the handle (ball) moves twice that distance. My question is, is this about right? Does this provide adequate leverage to engage the gears comfortably, or do you guys use more or less movement at the handle. As long as I'm fabricating, It would be nice to know if I need to increase this to a 3:1 or 4:1 ratio (any other suggested ratio).

 

[Russ Noble]

Ox, I'm using a direct rifle bolt linkage. ie 1:1. This is good and easy to shift but I think your 2:1 would probably give you a nicer 'feel'. If anything the gap across the gate between the 1/2 and 3/4 planes is a little close so configuring a little more sideways travel could make it feel better.

It hasn't happened yet, but my gearchange is that quick that I'm always scared that on the change up from 2nd the lever mightn't go across the gate, and might pick up 1st instead of 3rd. I can't see that being helluva good for anything at max revs in 2nd!! I've missed the 3/2 downshift a couple of times and picked up 4th instead of 2nd. That's embarrassing but not terminal. I think it's the way I hold the lever, suits the upchange but not the downchange. Just another little wrinkle to look into in my spare time, maybe reconfigure the shape of the lever.......Or maybe it's just a matter of 'practice makes perfect'. I've got a heap of more important issues to sort at present so that's fairly well down the list! It's early days yet, getting used to the action may be all it takes.....I think your 2:1 will be fine, the effort required to change is minimal.

 

[Ron Earp]

Mine appears to be a tad over 2 to 1. The rod will travel about 0.82" from neutral when selecting 3rd gear, while the shifter will travel just a bit short of 2.0". While the shifter is "slow" it is reasonably precise and doesn't require a huge amount of effort. I like it, about right.

 

[Bill Musarra]

Russ,
I think you don't have to worry too much on the shift to third and hitting first. The syncros will try to speed up the spinning of the clutch which will take a second or two not allowing you to enter the gear(I think). Basing that on my experience I had in my younger days when I tried to explain to some friends riding with me that my Muncie 4 speed would go into first at any speed because of the syncros. To demonstrate it I took it up to 90 mph and tried to go into first. You guessed it the clutch exploded from the cintrifugal force. I wasn't as smart as I thought I was. I am assuming the 930 or most syncro setups follow that rule. Am I right or wrong on that??

On my 930, center shift, Toyota cable setup, I will have to measure the throws later and post it.

Bill

 

[Terry Oxandale]

Thanks for the verification on this ratio guys.

so configuring a little more sideways travel could make it feel better.

I wondered about that as I was investigating my needs. I seem I've lucked out there in that with the U-joint attached directly on the shift-rod's centerline, the increase in angle (at the handle) between the 1/2 and the 3/4 gates in increased by about 10% (yeah, not much, but at least it's and increase). Below are a couple of photos of the prototype connector without any roller bearings (to study its efficacy), and the lower photo with a modified steering U-joint that was dismantled, longer arms welded in place, and then re-assembled.

 

[Paul]

Hi Terry,

How'd the linkage work out, in the end?

Still wondering exactly how to do the linkage on my T70 with the 930 box.

Cheers.

Paul

 

[Terry Oxandale]

Paul,

It worked out very well. Not shown in the previous posts was the modification to the linkage to make it a pinch-bolt arrangement so I could adjust the shifter handle angle. Ratio and effort feels good, although I will probably need to work on the 1-2 gears/synchros (do I even know what I'm talking about) because they've always been hard to shift compared to the very easy 3-4 shifting. I also removed the last 3/4" or so of protruding shift rod at the back of the case to gain some additional clearance behind the bodywork, but probably would not do that again.

 

[flatchat(Chris)]

A few ideas in this thread, chaps :- www.gt40s.com/forum/rcr-forum-rcr40-rcr70-p4-mkiv/19354-another-first-australia-5.html