Pitman arm lenthening question??

Knowing that my corvair pitman arm rings----> forged . And that it is an inch or so to short for my appplication can i heat it up cherry and work it longer with an anvil and hammer ..

Or do you know where i can find a longer corvair arm than the stock one.

 

did a search but no help

 

You mean like a horseshoe? It would only get thinner that way, not sure where to get a longer arm, Corvair boxes were pretty popular till the supply ran out.

 

Ya I have been searching to no avail.

 

GM Pitman arms are good quality forged steel. Cut the Corvair arm and find a Z28 camaro or firebird v8 arm and cut the center out of it.
( they are long, straight and flat )
Use the center section from the donor arm . Deep vee the weld, pre heat, and weld it together hot. Bury it in sand or kitty litter ( preferably not used ! LOL )
I have welded many pitman arms for race cars ( and a few hot rods) .
No problems so far. BTW, the dirt track cars are considered "full contact" race cars...
Good Luck
Dave

 

Before you forge you must take the part to an engineering shop and ask them do do a hardness test Rockwell C scale is the most common but Vickers or Brinell are also widely used. This is easy to do any will most likely not be worth the trouble of writing out an invoice.
You can't forge anything at "cherry" red, way too cold. To forge alloy steels you have to heat to bright red/yellow, leave it to soak at this heat for 10-15 mins then forge or in your case draw out the arm 1". I would make sure the arm was way over engineered as a stock item before you reduce the size thru cross section. So if you do forge the arm do not hit the arm when the temp falls below dull red, also do not overheat bright yellow is too hot. When finishing use a slightly lower temp and do not leave any hammer marks in the job. (The sharp edge of a hammer mark is a weak spot). Slow cool the job. Now take the arm back to the engineer and have the hardness test repeated, if it dosn't reach the same numbers you will have to heat treat the arm. I'm ***uming you have a forge fire or a furnace. If you do have to heat treat post again or PM me for more info. Remember a Pitman Arm is a critical part, failure is not an option. If you have doubts about your ability to make this work don't do it. Remember, it's not just your life out there.

 

while i am not a metallurgist, stretching it sounds like a bad idea..and no offense to dave lewis , i'm not a big fan of cut and weld on a pitman arm either

there has to be a longer arm that could be swapped onto your box?

 

This is how I do them. Cut off the splined end and turn round with a shoulder. Flame cut an arm of the length or shape that you need and poke either a straight hole for a rod end or a tapered hole for a tie rod end in it. put them together and weld.



Over the years, I've done a few of them. The patterns are for flame cutting the arm blanks.

 

36-3, No offence taken..
The corvair spline is smaller than common GM stuff. Not a lot of options out there.
I have also built a few like GAB but never kept the pattern.. Nice work GAB !
The T-bucket cowl steering I am working on right now is similar. Welded splines into a steel sleeve, extend thru the cowl and bolt on an aluminum arm..
Dave

 

i think how gab-kc did it is the way to go

 

THanks, Im suprised speedway doesn't sell longer ones

 

Can you use shorter arms off your spindles??

 

Its a matter of making the centerline of the taper hole on the pitman arm travel farther which can ony me a achieved by lengthening the arm. I may just lengthen it by blacksmithing it but before that I check my Mechanic of Materials book to punch some number involving the Modulus of Elasticity of steel, Load, and other good stuff

 

In the picture the steering box is ma**ed out to the right clearly the left wheel could be sharper.

 

A shorter steering arm off the spindle has the same effect as lengthening the pitman arm. More than one way to approach this - as is the case with most things.

 

Mink,,, what your pics show is known as "ackerman"
Simply put, the inside wheel needs to turn more than the outside wheel in a turn..
(smaller radius inside, larger radius outside)
Show us a full side view. It is not a clear enough in this pic, but it looks ok.
Look at the angle of your draglink ( the link from the steering box to the front axle)
As long as it runs close to flat / paralell with the frame to minimise bump steer you will be fine.
IMO ,Only 2 reasons to lengthen the pittman arm...1= quicken the steering 2= correct bump steer.
Dave

 

so bend it in about a 1/2" at a time and check it ???

 

Dave

Thanks for your post.

I just had one of those "NOW I GET IT" (ackerman) moments.

Gary

 

Dammit gary

 

Looking from here, it looks like the steering arm at the front end of the draglink is too long.


Ackerman looks like too much between sides which indicates to me that the steering arms off the spindles are too short.

How long is the Corvair pitman arm eye to eye centers?

Vega pitman arms are right at 6" eye to eye.


The T-bucket gang has been using the Corvair box with great success over the years.

Seems to me that the Corvair pitman arm length is probably ok as is and you need to do some juggling at the steering arms on the spindle and the one at the front of the draglink.


Fwiw - my 32 roadster has an aftermarket pitman arm on its Vega box and it ended up 5" eye to eye after bending to shape.

Works fine, turns plenty sharp.

Especially so after I cut 1/4" off the stainless steering arm stop nuts.

(Today's aftermarket stainless steering arm stop nuts are the correct length for the commonly used hot rod aftermarket steering arms etc.)

Don't be fooled by thinking the wheels aren't turning too sharp.
They may not look like they're cranked over far enough to make a sharp turn, but most times they are.

 

Ryan, try for 4 3/4 from the center of the king pin to the center of the draglink pin. Then go from there.

Ackerman looks OK to me, that's what it's supposed to do.

Car is looking good, good job there.

Frank.

 

I would test drive that car before messing with the pitman and/or steering arms any more. It may be just fine. But if it isn't, then take that spindle off and bend the steering arm's pivot point a bit closer to the kingpin, maybe 1/2 inch like you said.

 

Looking again, it shows that the steering arm at the front of the drag link is pulling almost straight back so there's no way the left wheel can turn sharper.

I'd get that bit squared away and then work on the spindle steering arms.

Once that's done I'm sure you'll find the Corvair pitman arm is long enough.


Got any close-ups of the spindle steering arms - both sides.

That would help.

 

5.5 eye to eye for the corvair arm and 7.5 from the kingpin to center hole off of spindle arm