Yet another 915 gated shifter design.

[tdw28210]

This looks like a really great start on a possible new product. Couple suggestions:

Please post a video of the shifter in action. Many of us would like to see how it actually performs.

I'd suggest you change the knob end to allow it to accept standard 901/915/G50-type shift knobs. A lot of us have different knobs we really like ( i.e. wood 917 knobs, crest knobs, leather knobs) and would be very hesitant to leave them behind.

Keep up the good work and keep this thread updated.

[Ionizer]

Originally Posted by tdw28210

This looks like a really great start on a possible new product. Couple suggestions:

Please post a video of the shifter in action. Many of us would like to see how it actually performs.

I'd suggest you change the knob end to allow it to accept standard 901/915/G50-type shift knobs. A lot of us have different knobs we really like ( i.e. wood 917 knobs, crest knobs, leather knobs) and would be very hesitant to leave them behind.

Keep up the good work and keep this thread updated.

Thanks tdw28210 and everyone else for all the positive comments. This really is a pleasant forum to visit compared to some of the other motorsport enthusiast sites. Perhaps because most of us aren't 25 anymore?

I will try to bring a gopro the next time I go for a drive. If there are any good dry days left this season.

This isn't really a product. When I'm finished tweaking the prototype and move on to fabricate the final version I guess I could make a few extra but it will require buying a short shifter, the factory option version, and modifying it. And it won't be anytime soon, not before everything have been thoroughly tested.

Right now I'm waiting for a thick sheet of carbon fiber to replace the aluminium flat bar. Results will be posted.

[911pcars]

Review Tyson's post #4.

The shift lever attempts to transfer accurate shift actuation in the gearbox. However, the distance between gearbox and shifter is an expanse of sheet metal that has less than ideal rigidity. This means a lever sliding into a fixed "slot" in the shift housing won't necessarily result in a direct 1:1 relationship with what you want to happen at the end of the 4 foot shift tube, especially if the vehicle is under torsional twist as when cornering/turning.

Sherwood

[Flojo]

Sherwood, that is true, the rod length is a "problem" for the 915.
But, just a thaught..., given some "play" in the slots, this could provide the 915-neded "inacuracy".
Further, the slots would give guidance and ths avoid clearly hitting a wrong gear.
No?

[911pcars]

Originally Posted by Flojo

Sherwood, that is true, the rod length is a "problem" for the 915.
But, just a thaught..., given some "play" in the slots, this could provide the 915-neded "inacuracy".
Further, the slots would give guidance and ths avoid clearly hitting a wrong gear.
No?

That design as is would most likely be fine in a non-aggressive operating condition, but unknown otherwise. The wider the slot, the more forgiving how the lever selects the desired gear. Adjustable slots dedicated to each gear position might work.

House the shift housing, shift tube and support bushings/bearing in an unrestrained rigid tube/structure which is in turn bolted onto the gearbox and the gates should be more applicable.

Sherwood

[Ionizer]

Originally Posted by 911pcars

Review Tyson's post #4.

The shift lever attempts to transfer accurate shift actuation in the gearbox. However, the distance between gearbox and shifter is an expanse of sheet metal that has less than ideal rigidity. This means a lever sliding into a fixed "slot" in the shift housing won't necessarily result in a direct 1:1 relationship with what you want to happen at the end of the 4 foot shift tube, especially if the vehicle is under torsional twist as when cornering/turning.

Sherwood

Yes the lever is fixed in the gate slot but there is still a bit of play in all the bushings and joints that should leave room for the twist in the car body and engine mounts during driving. The fixed lever position have to be in the center of that play, leaving the transmission input shift rod under no tension except for when changing gear. That of course makes the entire setup very dependent of the condition of those bushings. More play means less throw to a point when gears won't engage.

Lets do some rough calculations.
If the normal un-gated lever can be moved freely from 9 to 10 degrees (or 5mm of knob movement) towards the drivers side when in first gear. The total play is one degree and the gate slot should hold it at 9,5. With the movement ratio from lever to shift tube being something like 1:3 that gives the body and engine mounts +- 1,5 degrees of allowed twist. That is over 20mm of deflexion for each meter of width.

I (or anyone) could easily set up an experiment to measure the twist in the car. Just remove the top plate and rubber. Select a gear. Pull the lever gently to one side with a rubber band to take out the play. Drive and observe the movement of the knob.

[ClickClickBoom]

Originally Posted by 911pcars

Review Tyson's post #4.

The shift lever attempts to transfer accurate shift actuation in the gearbox. However, the distance between gearbox and shifter is an expanse of sheet metal that has less than ideal rigidity. This means a lever sliding into a fixed "slot" in the shift housing won't necessarily result in a direct 1:1 relationship with what you want to happen at the end of the 4 foot shift tube, especially if the vehicle is under torsional twist as when cornering/turning.

Sherwood

This, all the gates like this are installed on the transmission housing, eliminating the body flex conundrum. My bet is the factory tried it and discarded it when it didn't work, in fact if the body and engine/trans mounts flex using this type product, you will have in essence created a torsion bar system with your shift linkage. My bet is at a minimum you will have some sort of clicking-clacking noises as the trans/engine shifts on their mounts. The factory isn't using this system for a reason. If it were used in a roll caged car with solid trans and engine mounts it could work, but that is slightly different than this discussion.
Ultimate answer, no one sells them for a reason, they don't work as intended.

[JWest]

Originally Posted by kent olsen

I've had the Rennshift for many years. It has been adequate and I have replaced the bushings twice I think. I have always wanted something like your design and similar to the shift gates in the Ferrari.

Last spring I saw something similar on another RGRUPPE members car but forgot to write down where he got it, darn. His was just a plate that sat over the shifter. My Rennshift has a little to much lateral movement while in gear for me.

For me it's just a little more positive, just a glance if you need to confirm where you are. Even on the track, which I frequent, the shifting is done before or after the corner so you are already in gear.

Send the RennShift back to me and I will get rid of any lateral play in the spring gates - there should be none.

[Flojo]

Maybe it's less technical they didn't offer a gate.
Maybe it's just because of the tower not allowing a nice design place for a gate.
The center console is very low, the tower protruding, not as neat as those embedded gates in Ferrari/Maserati.

If the gates leave lateral play, it should work. At least for all those many not throwing their cars in twists while changing gears. C'mon...

Whatever, I love to try it!!

[Ionizer]

Originally Posted by ClickClickBoom

My bet is the factory tried it and discarded it when it didn't work

Except it works as the factory shifter does in 5th or R.

Originally Posted by ClickClickBoom

in fact if the body and engine/trans mounts flex using this type product, you will have in essence created a torsion bar system with your shift linkage

Yes, but only if the body flex exceeds the shift linkage play.

Originally Posted by ClickClickBoom

My bet is at a minimum you will have some sort of clicking-clacking noises as the trans/engine shifts on their mounts.

I haven't noticed any during driving, on the other hand I have a loud exhaust. In 3rd or 4th I would expects some rattling where there is no spring tension. A closeup with a gopro on the gate should reveal any clicking or torsion in the linkage.

Originally Posted by ClickClickBoom

no one sells them for a reason, they don't work as intended.

The shifter "works", ther's no question about that since I've driven the car a few times with it now (Sorry, didn't make any video yet as I promised). The only question is if it will cause any long term damage to the transmission. My calculations says no but more tests will follow.


My guess is that Porsche didn't want to make a fully gated shifter because it requires a precise adjustment of the coupler and frequent replacing of the bushings.

[lrodri64]

Subscribed
Really interesting

[sc_rufctr]

What someone should do is adapt a cable shift setup for our cars... Once adjusted I'd bet it would work perfectly regardless of what the chassis is doing. (Cable bracket on the gearbox) There are some very good reasons why most if not all modern manual cars have a cable shift.

This is a setup for a mid engined car.

[Speed metal]

Originally Posted by sc_rufctr

What someone should do is adapt a cable shift setup for our cars... Once adjusted I'd bet it would work perfectly regardless of what the chassis is doing. (Cable bracket on the gearbox) There are some very good reasons why most if not all modern manual cars have a cable shift.

This is a setup for a mid engined car.

This.

[ClickClickBoom]

Originally Posted by Ionizer

Except it works as the factory shifter does in 5th or R.




Yes, but only if the body flex exceeds the shift linkage play.




I haven't noticed any during driving, on the other hand I have a loud exhaust. In 3rd or 4th I would expects some rattling where there is no spring tension. A closeup with a gopro on the gate should reveal any clicking or torsion in the linkage.




The shifter "works", ther's no question about that since I've driven the car a few times with it now (Sorry, didn't make any video yet as I promised). The only question is if it will cause any long term damage to the transmission. My calculations says no but more tests will follow.


My guess is that Porsche didn't want to make a fully gated shifter because it requires a precise adjustment of the coupler and frequent replacing of the bushings.

All good, I am anything but a factory stock purist. The list of mods on my car is long and almost tedious. While I applaud anyone who wants to make their car better, but it seems like some products/ideas are to solve for a maintence shortcoming. I have a Seine Shift installed on my car, Rebel Racing semi solid engine and trans mounts, new cup bushing and detailed shift rod adjustment. My car is the best shifting manual transmission vehicle I have ever driven, at 60 years old, I have never owned an auto trans vehicle. Given the design of the synchro’s and 60 year old design, the transmission works superbly. I will submit the gate was either tried and the manufacturer decided it wasn’t necessary. The elegance of the good Dr’s design is balanced between cost and benefit realized. Anybody who might be having shifting imprecision check all the existing system components. The Darwinian concept basically shows that almost every shift tower gate design has a short production run followed by discontinuation. But if CNC milled parts are desired for esthetics, that’s a different horse.

[Ionizer]

Originally Posted by sc_rufctr

What someone should do is adapt a cable shift setup for our cars... Once adjusted I'd bet it would work perfectly regardless of what the chassis is doing. (Cable bracket on the gearbox) There are some very good reasons why most if not all modern manual cars have a cable shift.

This is a setup for a mid engined car.

That's what I looked at first when I started thinking about this 10 years ago.

http://forums.pelicanparts.com/porsche-911-technical-forum/363337-cheap-wire-shifter-discussion.html

A cable shifter have several benefits but it doesn't come with a spring return. There would still have to be springs and a gate added inside the shifter to achieve what I want . And it requires cutting a big hole in the car to attach brackets to the transmission.

In a mid-engine car like the 914 there might be more room but in a 911 all of the linkage and cables would have to fit inside the tunnel or be visible above the carpet.

For those reasons I decided against cables. If I ever cut the torsion tube to add a G50 and coilovers I will look at cable shifters again.