more throttle linkage..

davygrvy · Post by **davygrvy** » Tue Sep 14, 2004 3:54 pm

Plastermaster wrote:I think the circle Davey has used keeps it constant but increases the amount of cable pull to open the throttle.

Not just circles, but *groovy* circles.

brianwheelies · Post by **brianwheelies** » Tue Sep 14, 2004 6:16 pm

someone needs to design a new linkage system. i started with a Scat center pull, it didn't work. next went with a cb hexbar system, couldn't get it to work. now i have the redline/weber linkage and the fit is by far the best and the geometry good too but it is impossible to get a smooth and full throttle action out of it. this is on 40 idf's.

MASSIVE TYPE IV · Post by **MASSIVE TYPE IV** » Tue Sep 14, 2004 6:35 pm

I'm working on it. Mine will be vastly different though. The liability of making a throttle assembly is so huge. all it takes is one teenager to stick his throttle wide open and he will own my shop.

davygrvy · Post by **davygrvy** » Tue Sep 14, 2004 6:43 pm

This one?

It's all about the geometry.. I mean literally the math. If part#8 was a circle, linear pedal travel will equal linear turning motion. Being an "arm" there and at the throttle linkage means you've got a non-linear system. As the arm aproaches and then passes 90 degrees compared to the cable, the cable motion to turning motion is constantly changing with 90 degrees being the least and greater as it gets farther away.

If part#7 was at an angle to (14) such that it started at a tight (or acute) angle gaining to 90 degrees, it would produce a progressive action.

Got any pics of your setup? What are the dimensions of things?
1) Part#7 center to heim joint
2) part#8 center to cable mount point
3) length of linkage rods from heim to heim
4) angle of part#7
5) angle of part#8

I'll try to help, if you want.

brianwheelies · Post by **brianwheelies** » Tue Sep 14, 2004 6:51 pm

it's this one
http://redlineweber.com/html/linkage_se ... nkage_.htm

brianwheelies · Post by **brianwheelies** » Tue Sep 14, 2004 6:57 pm

the Scat center pull gave me he!!

it would stick all the time and really drive me nuts. made me want to burn the car. i wouldn't mind doing a servo operated throttle ala r/c equipment. if it failed, you'd be stuck though. cables sound pretty cool, no geometry nightmares and would be pretty easy to accomplish.

davygrvy · Post by **davygrvy** » Tue Sep 14, 2004 7:02 pm

Oh, that's very close to the CB one.

I know what I'd do...
1) Make part#8 a circle like the way I did mine, with a groove down the edge for the cable to fit in. {this gets things linear}
2) Set part #4&5 about as high as they can go and you'd do it by lengthening part #17(s) {this adds progression}

To get the radius you need for the circle, you need to do some math to solve for it. I can help if you want.

davygrvy · Post by **davygrvy** » Tue Sep 14, 2004 7:09 pm

brianwheelies wrote:i wouldn't mind doing a servo operated throttle ala r/c equipment.

I plan to do that for my enrichment circuit

brianwheelies · Post by **brianwheelies** » Tue Sep 14, 2004 7:21 pm

i haven't done any mods to this system yet just fiddling with the geometry and i can get full throttle if i use the inner most cable attachment for the arm the turns the hex bar. increases leverage at the expense of feel and cable rubbing against the tube. right now i have the cable attached to the middle hole and it provides a nice smooth action but i can't get to full throttle but it's not too far off like in the furhtest hole out. the cb doesn't have the adjustability that the redline linkage has. the arms that push the rods down have two mounting holes to choose from and i use the ones that have the best leverage(the furthest ones out). i've been thinking that i can make a bracket that attaches to the arms that would allow a third hole even further out that would allow for more leverage. so a piece of metal flat with three holes, two to attach to the actual arm and the third to mount the rods further out for more leverage. hope this makes sense.

davygrvy · Post by **davygrvy** » Tue Sep 14, 2004 7:53 pm

brianwheelies wrote:hope this makes sense.

It does. I fought the same fight.

How far out from the center is the second mounting point on the "Cross bar clamp on lever" (parts#4 or 5)? IOW, what is its radius, about 8.5 centimeters?

What is the angle it starts at? Is it 9 o'clock looking from the alternator to the driver's side carb for idle?

What is the angle it ends at for full throttle? About 7:30?

Does the bottom heim joint travel 3cm in a downward direction from idle to full?

What is the length of the linkage rods from top heim to bottom heim at the pivots?

From the pivot of the cross bar, how far up is it from where the bottom heim joint mounts to the carb's linkage at idle?

From that I can calculate the geometry on the bar and solve for the throttle arm.

Plastermaster · Post by **Plastermaster** » Tue May 17, 2005 8:57 pm

MASSIVE TYPE IV wrote:Yep.. the opening event is rapidly increased.. You can move the cable attaching point behind the pedal to slow it down also..

Jakes post is about the only one here looking at the other end of the cable, so I thought I would take a look at it.
I have always had issues with the linkage on my old engine. My problem was more getting it all dialed in so that the throttle would be closed at idle and still open up the whole way when I floored it. But that was more to do with the arms on my center pull linkage. Just like this thread, all my attention was under the deck lid. Now that I am installing the engine Jake sent me for my birthday (eat your hearts out guys) I had to replace the throttle cable. So I got a good look at how things work on the front end of the cable, and noticed a few things that relate to the progression of the throttle. The "C" shaped underside of the pedal that runs on the roller to push it forward has a very indirect push on it in the begining of pedal travel. However the pedal needs to be standing up pretty straight (uncomfotably so) in order to take advantage of that slow spot. After that initial say 20% of pedal travel that gives you say 5-10% of throttle, the progression becomes linear. Maybe I'm the odd ball here but I always had it set up so that when the pedal was to the floor I was at full throttle, and never made use of that soft area at the beginning of the pedal. It looks like if I set it so at idle the pedal is all the way lifted, and use the carbs to stop the pedal travel at full throttle, the intitial tip in will be pretty gradual.

Ron

Ephry73 · Post by **Ephry73** » Wed May 18, 2005 6:15 am

Jake, how about releasing the bellcrank linkage with a waver form? I'll sign one.

The linkage looks good. I didn't have this problem with my Cali conversion, as that conversion uses the stock type 1 cable routing. When I switched to the DTM, it definitely felt different. I (just recently) cut off 2.25" off the guide tube for the linkage, and this made the pedal so much better. I will try to change the angle of the "down arms" to get a better feel.
The pedal has full travel, and the WOT matches the pedal location, but the pedal feel too soft, in relation to how the engine feels. This made the clutch/accel relation a bit off (backed the new A-1 muffler pipe into a parking boulder while buying oil for the car)

.

Maybe relocating the guide tube to the type 1 location will help? or close to that?

Either way, I will try to "emulate" your changes, and see how much more better pedal I get.

On the other hand, since we have a different clutch/flywheel arrangement, how should we set the clutch pedal "play"?

Plastermaster · Post by **Plastermaster** » Wed May 18, 2005 7:05 pm

On the other hand, since we have a different clutch/flywheel arrangement, how should we set the clutch pedal "play"?

Good question, I was gouing to set it with the same free play as before since no one has ever said anything different.

Today I installed the carbs and the linkage and it looks like there is less travel at the lever where the throttle cable attatches then I had before. The arm is at least twice as long as the scat centerpull I had before. I will try it as is, but if the pedal travel is too short it would be an easy fix to increase the length of the arms that are on the carb. Not the ones that drop down, but the flat brass taperd ones that the balls attatch to.

Jake says he hasnt had a problem with any of this. Might have something to do with the way he drives?

Ron

Ephry73 · Post by **Ephry73** » Thu May 19, 2005 5:51 am

He does push 'em!

Well, I even have the little adapter tabs to move the linkage up and out. So far shortening the guide tube helped. I will try to play with it some more. With school and work, I haven't had much time but just to start the engine and such.

I would love to have a bellvrank linkage for the engine though.

Jake, what if the oil cooler shroud is modifyed a bit to give clearance to a bellcrank linkage like the ones that mount on the back of the block(ie? CSP style ones)

Just curious.

Ephry

Plastermaster · Post by **Plastermaster** » Thu May 19, 2005 9:24 pm

I guess shortening the guide tube helps reduce the throttle cable having to change angle as it enters the tube. It might help if there were a bowden tube before the guide tube to give the cable a better shot at it. You might even bend the guide tube, but it might be hard to run it through the shroud if you did.

Ron