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Engeneering challange ... Progressive Throttle Linkage

dagodagoMember
I had my first time out with the Cat last week on the Zandvoord GP cirquit in Holland after a small project running out of control.
Ended up with an all alloy 100KG lighter racing engine. First try was great, No tecknical problems at all. Car was insane fast. But I have one big problem. The engine has a Kinsler velocity stack. The butterfly valves open way to fast. So there is no power control in the turns. It is either no power or to much power.
So I am looking for a throttle linkage that will give a proportional response to the gas pedal. Something like a eccentric wheel.
However there is only very limited space. The engine is real close to the bulkhead. The two shafts with the butterfly valves petrude the velocity stacks just below the window. On the shaft where the linkage arms are mounted is only 1 1/2 inch of space. There has to be a travel stop, a linkage to the other side ( the remaining 4 tacks ) and a control arm or wheel to move the shafts, on this 1 1/2 inch.

So any good ideas how to make a proportional throttle linkage?

Arno
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MT mike the snake (Guest)
If you check my thread "IR injection maintenance" a couple threads down, you can see how mine is set up (not the greatest pic), and others have drawn up a few different combinations.

I've seen another cool setup that had a wheel that mounted in between the stacks, that the cable went to, and the rods that actuated the butterflies came off of the wheel.

This I think could be made to be very progressive.

Here's a link to the thread with the pic of the linkage system I described. it looks very cool too.

http://pantera.infopop.cc/eve/...0045562/m/4121066556
dagodagoMember
Good thinking Kid,
I was thinking aboud somekind of sliding linkage at the gaspedal. But then again, I saw myself head down under the dash again. Right feet out of the left door, left feet out of the right window. Left arm folded up 3 three times under my body, and only two fingers availlible for work on my right hand. difficult for a lefty. don't we hate that all.....

Mike, it is real hard to make a propportianal linkage just with arms. It is possible though as long as the two shafts rotate the same direction. mine are counterrotating. The wheel in the middle is not so bad idea. Have a look at this.

http://www.gktech.com/index.ph...-throttle-wheel.html
MT mike the snake (Guest)
That eccentric wheel looks like it might work well for your needs.

My setup the cable comes from the side, and goes directly to the cross-connecting rod that joins the two halves of the linkages. It is very progressive, but has a long pedal travel.

I'm just running what was on the car when I bought it. The cable was routed such that it melted against the header, so I'm expecting my new replacement wednesday.
jfb05177jfb05177Member
photos or a sketch would be nice if you wanted an answer

the eccentric wheel throttle should provide the progressive throttle response. the one thing I would recomend would be to add self alignment to the cable shield support to reduce the cable bending as it enters.

with out knowledge of your setup,it would be hard to provide any detailed suggestions
jfb05177jfb05177Member
replacing the throttle arm with an eccentric wheel should do fine for your arrangement.
thinking...the eccentric wheel is basicaly a reducing radius arm so why not use multiple arms of varing lenght. I would think just one long arm would give you what you want.

if you can add some info like
total throttle cable travel
butter fly total travel angle
how much reduction of opening in the bottom end
open angle at which to increase opening rate

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ausfordausfordMember
Anytime throttles are actuated with a arm there will be a change of rotational velocity relitive to the angle of the arm.

What this gives you is a lot of throttle shaft rotation for a given pedal movement just off fully closed, then less rotation for a given pedal movement around 1/2 throttle and finally a lot of rotation for a given pedal movement as you approach full throttle.

So you get a variable ratio as you move through the throttle range but in the exactly opposite way that is desirable.

I think that eccentric wheel could be a good remedy for your problem but just a plain concentric wheel may give you the improvement in throttle feel you seek as it will eliminate the varing ratio of the arm you currently are using.
jfb05177jfb05177Member
quote:
Originally posted by Aus Ford:
Anytime throttles are actuated with a arm there will be a change of rotational velocity relitive to the angle of the arm...

running some numbers in excel, comparing a throttle arm set for +/- 45 degrees with a wheel shows at the begining you get more butterfly opening for less pedal. while the wheel looks like a small advantage in linearity, the great advantage is the reduction of the force resulting in loading on the butterfly bushings. at 45 degrees, the force that results in forcing into the bushings is equal to force being used to rotate.

when I get some more time I hope to add a 2 arm arrangment into excel

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kidkidMember
quote:
Originally posted by Dago:
looking at the front of the engine


That is like the "over-under linkage" from the Kinsler catalogue, and my experience too is that with this setup, it is really hard to get the butterflies from both banks to move perfectly simultaneously...(if not impossible).

I gave up, and changed the connection in between the banks.
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