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Does anyone else have problems with linkages flexing or the bell crank being too loose or too tight?

I spent a little time tinkering with the R1 project yesterday and just not happy with the mechanicals on the shifter linkage.
There is a long aluminum linkage that's way to flimsy. Then there were two other steel tube linkages that came with the project, one works part of the time, the other is too long and puts the shifter at an odd angle.

Thinking about dumping the linkaage in favor of a heavy duty push/pull cable. thoughts?

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Too much week, not enough weekend.

OOPS I did it again
http://www.locostusa.com/forums/viewtopic.php?f=35&t=17496

Blood Sweat and Beers
http://www.locostusa.com/forums/viewtopic.php?f=35&t=15216

I used 3 bellcranks and 10 rodends in my shifter though it is a car transmission. I had to take radial motion and convert it into longitudinal motion and vice versa to convert from a cable shift in the MR2 to mechanical linkage. Push pull cables are used a lot but I do NOT like the "flexy" feel of them.
Chuck (rx7locost) drove my car recently and commented favorably on the shift linkage.
The linkage is viewable on page 3 of my build log.

JMR

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When you're racing, it's life. Anything that happens before or after is just waiting -- Steve McQueen from LeMans

My build log viewtopic.php?f=36&t=10658&start=0 NOW NAMED =The Wycked 7

My other build log viewtopic.php?f=18&t=15162 The Skayt'R6

I see a problem with my setup right off the bat and it's something I suspected yesterday. The bellcrank is a single and the rod ends attach to it with a small 10-32 machine screw. The bellcrank itself attached to the frame with a 5/15-18 bolt and that bolt can rock side to side when pressure is applied.


To the drawing board.

_________________
Too much week, not enough weekend.

OOPS I did it again
http://www.locostusa.com/forums/viewtopic.php?f=35&t=17496

Blood Sweat and Beers
http://www.locostusa.com/forums/viewtopic.php?f=35&t=15216

I agree with Kartracer. In my experience, including bike engines in (FSAE) cars, linkages should typically feel superior to cables. Sounds like you're already on the right path in hunting down the under-constrained part(s) of your mechanism.

_________________
-Justin

"Orville Wright did not have a pilots license." - Gordon MacKenzie

Kartracer47, I am home now. Got in late last night. Thanks for a great day. Please thank Dave too.

I sent TooBusy a PM earlier suggesting he contact you about your shifter mechanism. It certainly felt great to me. Glad to see you post here. He would do well to follow your lead. I wish my RX7 trans shifted as positive as your system.

Chuck

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Chuck.

“Any suspension will work if you don’t let it.” - Colin Chapman

Visit my ongoing MGB Rustoration log: over HERE

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tipically, an inline cable shifter would require two cables,one to operate the shifter and one as a reaction to allow for engine mount movement, this would make a more positive shift.

with a bell crank system, the tightness of all the linkage is critical and the more bell cranks in the system, the more play, if the bell cranks are mounted on the chassis and the engine has any flex in the mounts then that would translate into play or poor shifting.

_________________
this story shall the good man teach his son,
and chrispin chrispian shall ne'er go by,
from this day to the end of the world.
but we in it shall be remembered.

Clarification needed - Cable shift system - one cable transfers for and aft motion of the stick and the other cable transfers sideways movement of the stick. The cable housings isolate the motion of the engine/trans from the chassis.
I used 3 bellcranks in my system. 2 of the bellcranks transfered the motion of the stick and the 3rd was the isolation bellcrank to minimize motion transfer from the engine/trans. My linkage (3 bellcranks with oilite bushings and 10 good rodends) is tight, positive and isolated from the engine/trans movement!

The accompanying picture shows all 3 bellcranks and their linkage. The center one (against the firewall) is the motion isolator. The one on the right takes the fore/aft motion of the stick and rotates the transmission shift rod, The bellcrank on the left takes the stick rotation and moves the shift rod in and out.

JMR

Thank you Chuck - enjoyed the visit and glad you had a safe trip home. I will relay thanks to Dave.

_________________
When you're racing, it's life. Anything that happens before or after is just waiting -- Steve McQueen from LeMans

My build log viewtopic.php?f=36&t=10658&start=0 NOW NAMED =The Wycked 7

My other build log viewtopic.php?f=18&t=15162 The Skayt'R6

Thanks for the replies guys. I spent a few minutes in the garage last night tinkering. My issues are due to insufficient rigidity of the mounting points and the linkage.

The shifter has some play between the bushings and the mounting shaft. Getting UHMW bushings cut at work
The bolt for rod end to shifter isn't rigid. A little weld bead will take care of that
The bolt for bell crank to frame has play. Weld in place
The bolt for both rod ends to bell crank have play. Weld bolt or redesign bell crank for double shear mount
The linkage rod flexes. go to larger OD tube.

_________________
Too much week, not enough weekend.

OOPS I did it again
http://www.locostusa.com/forums/viewtopic.php?f=35&t=17496

Blood Sweat and Beers
http://www.locostusa.com/forums/viewtopic.php?f=35&t=15216

Check out push/pull cables. McMaster, Pegasus, Summit and several others sell them. Just be sure to get a low friction one that allows for a tighter bend radius - I believe they're typically black.

Here is my set-up on the formula car:



The layout in the photo is a pretty straight line from the shift lever to the linkage on the engine so I didn't install a set of return springs on the shift lever. If I ever get around to cleaning this one up I'd add a set of positive stops and a set of return springs on the shifter lever. If your routing is more complicated you will want the return springs.

_________________
-Andrew
Build Log
Youtube

My routing is pretty straight with one large radius 90 degree bend.

That's a nice simple setup

_________________
Too much week, not enough weekend.

OOPS I did it again
http://www.locostusa.com/forums/viewtopic.php?f=35&t=17496

Blood Sweat and Beers
http://www.locostusa.com/forums/viewtopic.php?f=35&t=15216

Kartracer, yes, that is correct, the left/right motion of the shifter is usually transfered to up and down at the trans selector shaft and the fore/aft is transfered to a rotation of the trans selector shaft.

the cable outer sleeves must be attached securly at each end.

however a gate is usually required at the shifter end with a reverse lock out.

some cars have a fixed rod attached to the shifter and the trans so the whole shifter moves with the engine and do the shifting with another rod that rotates and moves fore and aft.

on a quere box as on a bike, with the shiftg in a linear plane, then only one cable is required but the cable must be capable of pushing as well as pulling, again the outer sleeve must be securly fastened at both ends, neutral poses a problem, because it requiese a sprung loaded shifter as positive neutral detent but first and second may be either side of neutral so some jiggery pokery must be used to engage first and pass through neutral to second without the detent operating until the lever is moved back to neutral from second, othewise it will stick in neutral when shifted from first to second.

fortunately, there is no reverse so no detent is required for that.

my suggestion for this situation would be a "J" shaped gate at the first/neutral end sprung loaded to the long legg, so you would move the shifter forward into first, the spring would then move the shifter sideways into the long leg, giving a clear shot backwards into second, third, etc. then requiring the shifter to be moved all the way to first then moved sideways against the spring and back into neutral where it could lock into a notch at the end of the short leg of the gate, held there by the spring.

_________________
this story shall the good man teach his son,
and chrispin chrispian shall ne'er go by,
from this day to the end of the world.
but we in it shall be remembered.

in my shop we tend not to do any shifters with bellcrank shifters unless we have to .
many times there are more parts to wear out and more end link that need ajustments .
when it comes to it giving a better feel than a push / pull cable that depends on many other things in the design of the system it's self . if your using the gear box of a motorcycle they tend to have cam style shifters move the lever up of down to change gears . they tend not to have the feel of say a H-pattern shifter would need to have .
on one of my cars it had a bellcrank and solid rods the guy that built the car designed it so you have to move the motor to ajust the chain . every time you did that you had to go back and ajust the shifter and the throttle cable . after the 1st chain ajustment i did i changed the set up to were the mounts for the two to the motor it's self and changed out the bellcrank to a push / pull cable . because the old mounts were mounted to the chassis the new mounts now are on the motor so you can move the motor and not lose the ajustments of the cables .

Check the auto salvage yards for cheap sources of quality push/pull cables used on automatic transmission cars... even mid-engine cars like Fieros & MR2's had good usable cables & shifters that can be easily modified for straightline use.

bryan

There are also marine steering and shifting cables that are long, tough, and cheap.

For throttle pull-only, I'm using a teflon lined 5mm brake cable housing (about $10 for 10 feet) and a 7x19, 316 stainless steel wire rope (about $10 for 10 feet). Bought longer than I needed. It's hard to cut it longer.

i've cut my cable three times now and it's still too short!

_________________
this story shall the good man teach his son,
and chrispin chrispian shall ne'er go by,
from this day to the end of the world.
but we in it shall be remembered.