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Re: Subtracting Weight from the Autocrosser
Posted by: BobV66Vair ()
Date: August 27, 2017 09:10AM

Jonathan, did you eliminate the windshield washer and wiper mech? That seems like some weight you don't need, unless it is required for class to keep them.

I have also wondered if racers put a solid plate under that front cowl to keep the air from collecting there. Just under the slotted cowl so no air even gets started down the inside.

Bob Vinnacombe
Sandy, Oregon
1965 Corsa 140 stock
1966 Monza Soon to be race car
1968 Monza Parts for now

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Re: Subtracting Weight from the Autocrosser
Posted by: Jonathan Knapp ()
Date: August 28, 2017 10:47PM

Dan -

Gotta have wipers for my Street Modified class. I did take out the wiper washer bottle and bracket.

I made a conceptual error in my first design for the drag link on the steering, so I am having to re-engineer that a little bit. I hope to have that completed soon. I'll post pictures when it is done.

Johnny -

You wanted to see pictures of the Sadek 7/8" hollow front sway bar. Here they are. I have the car back up in the air to do more work on the steering and the front shocks are out. Front-to-back spacing of the Heim joint on its bolt was fairly critical. If it is too far forward or too far back during suspension travel it will bind on the sleeves around the bolt. Similarly, look closely at the bolt that holds the lower Heim joint into the end of the sway bar. You will see a tiny short sleeves that space the Heim joint away from the end of the bar and away from the bolt head. Without these the lower Heim joint would also bind.


Jonathan Knapp
Seattle, WA
'66 Corsa Autocrosser

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Re: Subtracting Weight from the Autocrosser
Posted by: Jonathan Knapp ()
Date: August 29, 2017 11:24PM

I got the welding done on my new steering drag link today. Still more work to do to get it painted and on the car, but today was a milestone as it took a lot of detailed cutting and grinding to make the pieces fit together precisely.

First up is the jig I built (twice, really) to hold all the pieces in the correct relationship for welding. The second picture is a close-up of the MIG weld. I tacked the pieces together on the jig with the TIG, but then used the MIG to get good penetration and fill the gaps. Finally, the finished product standing on edge from a front view.

Jonathan Knapp
Seattle, WA
'66 Corsa Autocrosser

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Re: Subtracting Weight from the Autocrosser
Posted by: Jonathan Knapp ()
Date: August 29, 2017 11:34PM

More pics of the finished product from different angles. First, a top view; then a bottom view; last, a front view with the piece laying flat on table top. Gusset is clearly visible in the top and bottom views.

Everyone should understand that the inner tie-rods will attach to the holes out at the ends of the lower part. This is where the change in steering geometry comes from.

The lengthened lower bar with the front-to-back gusset, welded onto the bottom of the stock drag link, should be plenty strong and resist flexing.

Jonathan Knapp
Seattle, WA
'66 Corsa Autocrosser

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Re: Subtracting Weight from the Autocrosser
Posted by: 283corsa ()
Date: August 30, 2017 08:09AM

Don't see my last post but do you have availability of more rear lexan back lights? Thanks Dan

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Re: Subtracting Weight from the Autocrosser
Posted by: 283corsa ()
Date: August 31, 2017 07:55AM

My post still does not show up, do you have a source for more rear back lights? Thanks Dan

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Re: Subtracting Weight from the Autocrosser
Posted by: Jonathan Knapp ()
Date: September 01, 2017 11:27PM

Dan -

It's been so long since I did the tail lights, I don't have any more information about them. Look back on page 3 of this thread. Matt Nall had some info about something that looked real similar.



I finished up on the remade steering drag link project today. It is all installed now. As always, there were several unforeseen elements that had to be overcome. First off, I ended up needing 3 stock drag links to make one that has the rigidity and geometry that I wanted. Most of the left side of one; most of the right side of another; and then a third one across the top to weld my new longer piece to (you'll see what I mean when you look at the pictures). I started off thinking I could do it with two. Thanks to Dick Hull for allowing me to pick through his Corvair bone yard to come up with the pieces I needed.

The real challenge was that the metal moves around a tremendous amount with the heating and cooling of welding. After welding everything up, sand blasting it, and painting it, I ended up having to reheat and bend the ends slightly because the ends no longer aligned with the idler stud and the pivot bold hole in the Pitman arm. That meant removing the bushing, heating and bending, allowing it to cool, blasting it again, reinstalling the bushing, checking the fit, removing the bushing again, heating and bending again, allowing it to cool again, blasting it again, reinstalling the bushing again, checking the fit again (correct this time), removing the bushing again, painting it again, reinstalling the bushing again, and then finally installing the piece on the car.

Speaking of the bushing. I used the Delrin piece that I already had in the other drag link. But I was surprised at how different the inner diameters of the two bushing sleeves were. I had to turn the bushing down about .035" to get it to fit. I turned it down so that it had about .004" interference fit with the sleeve. This squeezed the Delrin down slightly on the inner hole. I had two pivot bolts. One was .001" larger than the other. The smaller one slipped right in by hand. The larger one would not go in at all.

Here are some pics.


Jonathan Knapp
Seattle, WA
'66 Corsa Autocrosser

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Re: Subtracting Weight from the Autocrosser
Posted by: Jonathan Knapp ()
Date: September 01, 2017 11:33PM

Here are more pictures of what it looks like completed. I had to order new tie-rod adjusting sleeves from Speedway. The new ones are 3" shorter than the old ones.

These pictures give you a sense of what it looks like with the wheels pointing straight ahead.

Jonathan Knapp
Seattle, WA
'66 Corsa Autocrosser

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Re: Subtracting Weight from the Autocrosser
Posted by: Jonathan Knapp ()
Date: September 01, 2017 11:44PM

Here are more pictures of it turning left and right and also from below.

Close observers will notice a couple of things. I put a zerk fitting in the forward joint of the idler arm. When I had it off, I noticed how stiff and dry it seemed. After drilling it for the zerk fitting, I let it soak in solvent over night. I blew it out with air the next morning, installed the fitting and shot it with grease. Much smoother action now.

On the other end of the drag link I installed a washer between the bottom of the Pitman arm and the top of the top of the pivot/bushing hole. This is because, with a bushing that is not bonded to its sleeve (like a stock rubber bushing), the drag link end can work its way upward on the bushing. The washer prevents this movement.


Jonathan Knapp
Seattle, WA
'66 Corsa Autocrosser

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Re: Subtracting Weight from the Autocrosser
Posted by: martyscarr ()
Date: November 21, 2017 06:24PM

Today I went over to a friend's house who has been making a few parts out of carbon fiber. His latest effort is this carbon fiber turkey roaster. It is 3 layers of carbon fiber bonded with high temperature epoxy. It weighs 399 grams (.88 pounds) It will be a little less after he drills out the spark plug boot holes smileys with beer

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Re: Subtracting Weight from the Autocrosser
Posted by: Seth Emerson ()
Date: November 21, 2017 06:40PM

So, your intent was to move the inner pivot point to the same location as the lower control arm inner pivot point. That is what it looks like. Have you relocated the outer location, the end of the steering arm pivot point, relative to the stock arm tip location?

Seth Emerson

Check my new Performance Corvair Web site [www.perfvair.com]

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Re: Subtracting Weight from the Autocrosser
Posted by: isucorvair ()
Date: November 22, 2017 07:24AM

martyscarr Wrote:
-------------------------------------------------------
> Today I went over to a friend's house who has been
> making a few parts out of carbon fiber. His
> latest effort is this carbon fiber turkey roaster.
> It is 3 layers of carbon fiber bonded with high
> temperature epoxy. It weighs 399 grams (.88
> pounds) It will be a little less after he drills
> out the spark plug boot holes smileys with beer


Woah....that's pretty awesome.

I bet he could sell some of those smiling smiley


Eric P.
DeWitt, IA

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Re: Subtracting Weight from the Autocrosser
Posted by: chris ()
Date: November 22, 2017 07:52AM

isucorvair Wrote:
-------------------------------------------------------
> martyscarr Wrote:
> --------------------------------------------------
> -----
> > Today I went over to a friend's house who has
> been
> > making a few parts out of carbon fiber. His
> > latest effort is this carbon fiber turkey
> roaster.
> > It is 3 layers of carbon fiber bonded with
> high
> > temperature epoxy. It weighs 399 grams (.88
> > pounds) It will be a little less after he
> drills
> > out the spark plug boot holes smileys with beer
>
>
> Woah....that's pretty awesome.
>
> I bet he could sell some of those smiling smiley
>
>
> Eric P.
> DeWitt, IA

No kidding! That’s pretty impressive.

'65 Monza 4 door
4 speed
110hp
Gardner, KS

Heart of America Corvair Owners Association

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Re: Subtracting Weight from the Autocrosser
Posted by: BobV66Vair ()
Date: November 22, 2017 09:26AM

Jonathan, The suspension drag link looks good. Any idea what it will do to correct for Ackerman? Do you measure each wheel (F & R) from a center point on the I-beam? The geometry is staggering to me. Short of doing it 50 ways I am not great at sorting it all out!

Bob Vinnacombe
Sandy, Oregon
1965 Corsa 140 stock
1966 Monza Soon to be race car
1968 Monza Parts for now

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Re: Subtracting Weight from the Autocrosser
Posted by: Jonathan Knapp ()
Date: November 27, 2017 10:19PM

Bob -

My only concern for the drag link modification was to improve bump steer. The new drag link does not affect Ackerman at all. Ackerman is almost entirely a function of steering arm position. It is affected a little bit by the fore and aft position of the drag link (or the steering rack, if you have one); but the big and necessary changes in Ackerman a achieved by relocating the steering arms.

Correct steering arm location for correct Ackerman is not that hard to figure out. With the car sitting on its tires, make a mark on your floor directly under the center of the differential. Then make a mark on the floor directly under each of the front lower ball joints. Then move the car and draw two lines from the differential mark through and slightly beyond each of the lower ball joint marks. Anywhere on the line beyond the lower ball joint mark would be the proper placement for the steering arm end.

A position on that line beyond the lower ball joint mark may, or may not, be possible with you combination of tires, wheels, brakes and tire rod ends. My experience indicates that it is not possible with 15" or smaller diameter wheels because the steering arm would have to be too short to fit inside the wheel. Even with a stock steering box (as I run), the lock-to-lock turns would be way too low and the steering effort would be way too high. 17" wheels will definitely work; 16s may, but I am not sure. Even with smaller diameter wheels, getting close to the line will improve steering and cornering Gs significantly. The stock and aftermarket steering arms are located way too far inboard.

Marty -

Awesome turkey roaster! Is that Tom's handy work?

Seth -

When I redid my steering arms I used aftermarket IECO arm because they are beefier than the stock ones. Since I was increasing the force vector on the arms by shortening them (and also by using so much wider and stickier tires) I wanted them to have as much cross-section material as possible. I moved them outboard, but I did not move them up or down relative to the original position of the IECO arms.

At the time I built them, I was still running drum brakes. I relieved part of the inner edge of the drum and part of the backing plate splash guard that covers the bottom half of the drum's inner edge. This was done to move the steering arm as far outboard as possible. Since then, as can be seen in the pictures, I have gone to disk brakes. The up-and-down position of the steering arms turned out to be just right for the Wilwood calipers. Placing it any higher up would have created interference with the caliper.

Since moving the steering arms up was out of the realm of possibility, I opted to move the drag link down. This puts the tie-rod and the lower suspension arm in parallel. I moved the inner tie-rod end attachment point outboard so that the tie rod length and the lower suspension are length are much closer to the same (not exactly the some, but much closer) As they both move upward in suspension compression, they will now travel on the same arc.

Previously, with the lower suspension arm parallel to the ground and the tie-rod end sloping down to the outside, bump steer was extreme. Under compression the lower suspension arm moved toward the center of the car, while the outer tie-rod moved away from the center of the car (until it reached parallel with the ground and then it began moving toward the center of the car). Needless to say, this created a huge amount of toe-out under suspension compression.

With the lower suspension arm and the tie-rod parallel and with them pretty much the same length, the suspension and the tie-rod will travel through arcs that are pretty much the same. That should reduce my bump steer problem substantially.

Everyone -

Here are some pictures of my latest addition to the front suspension. After my old Bilsteins gave out, I had to find some new ones to replace them. Tim, the Bilstein racing tech guy in South Carolina, was a big help.

I found that the G-Body GM front shocks have the right external dimensions. Happily, they also are available in custom valving. With help from Tim I settled on what they call a 70/20 COB valving. I has fairly light compression dampening for the light front end of the Corvair. But we chose moderately heavy digressive dampening for rebound.

This should work well for autocross as the front end will stay planted and not pop up right away. This will be good for cornering as the front end will stay down when I release the brakes at entry into a corner and get back on the gas.

The G-Body shocks come with a tie-bar for a bottom mount instead of a tube. The tie-bars are bonded into the rubber of the lower bushing. I had to carefully cut the tie-bar from the bushing with an X-acto knife and then find some slightly larger diameter O.D. pipe to make a new tube. I pressed it in with RTV. Hopefully, that will lock it in place.


Jonathan Knapp
Seattle, WA
'66 Corsa Autocrosser

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Re: Subtracting Weight from the Autocrosser
Posted by: BobV66Vair ()
Date: November 28, 2017 10:15AM

Jonathan, is the angle of the tie rods going to be changed in future? It looks really close to the same as the lower CA already. Is there fine tuning that can be done or is the effort to make another drag link a diminishing return?

You are very generous with your hard found knowledge. I, for one, really appreciate that.

Bob Vinnacombe
Sandy, Oregon
1965 Corsa 140 stock
1966 Monza Soon to be race car
1968 Monza Parts for now

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Re: Subtracting Weight from the Autocrosser
Posted by: Seth Emerson ()
Date: November 29, 2017 06:33PM

Jonathan - Have you thought abought pressing out a lower tube and surrounding rubber from a Corvair shock -of some origin, then pressing both into the Bilstein? Not sure that would be better. Thanks for the additional info.

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Re: Subtracting Weight from the Autocrosser
Posted by: Jonathan Knapp ()
Date: December 01, 2017 11:06PM

Bob -

The point of my custom drag link was just that: to make the tie-rod parallel to the lower suspension arm. I did careful measurement and found that the outer tie-rod joint was 7/8" lower than the outer ball joint of the lower suspension arm. Therefore I lowered the drag link by 7/8" to make them parallel. To the extent that they do not look parallel in the pictures, that is a function of the position of the camera. They are, in fact, parallel. I don't really see any way to make the angle of the tie-rod end adjustable. But I also don't see a need to adjust it. It is now where I want it to be.

Also, by moving the inner tie-rod end outward, making the tie-rod basically the same length as the lower suspension arm, the arc that it travels through on a bump will be the same as the arc that the suspension arm travels through. As they move up and down, the amount that the arc makes them travel side to side will be the same, reducing bump steer to zero or insignificant.

Seth -

I didn't have any old stock front Corvair shocks around to try your idea, but it did occur to me. I did, however, have my worn out old Bilsteins. Turns out, however, that the design has changed some over the years. The lower eyelet on the newer Bilstein is kind of hour-glass shaped and the bushing similar. The old Bilstein has a straight sided eyelet and depends on the rubber overlapping the outer edge to keep the bushing in place in the eyelet.

I think my solution will work out okay.


Jonathan Knapp
Seattle, WA
'66 Corsa Autocrosser

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