Shortened Pitman Arm

Ford1930

Ford1930

Member
I am looking for information on the use of the shortened Pitman Arm.
Is it a intelligent thing to install this arm in place of the original? Does it need other changes? Can one still use the original Drag Link?
Does the use reduce the power needed to steer?
 
They are used a lot and they are fine. It does reduce the turning effort, but the turning radius goes up. I took mine off because I could not turn around like all the other cars when we had a breakdown. We call it a Chineese fire drill. All the cars trying to get back to lend a hand. Your drag link is fine.
 
Ford1930,
I put one on my 1930 Ford a couple years and actually I can't see a difference and I've been driving this car for 27 years.
Marty
 
I like mine (3) ! and I have noticed no reduction in turning radius. If a steering wheel is turned lock to lock the wheels are still turned the same amount.
Terry
 
I have had shortened pitman arms on two of my cars for 10 years. I like them because it lessened the effort to turn the steering wheel. My cars both still turn against the stops right and left. I have heard that some cars loose some turning radius. They may have shortened the arm too much.
 
Physics tells me that the effort to turn the wheel will be greater with the shorter pitman arm but you would turn the steering wheel less to have the same effect on the wheels.
 
wmws said:
Physics tells me that the effort to turn the wheel will be greater with the shorter pitman arm but you would turn the steering wheel less to have the same effect on the wheels.
Click to expand...


That was the way I thought of it at first too but I had it backwards. Try visualizing it this way. Hang a weight off the end of a regular pitman arm and then pick up the pitman arm by the other end. Then shorten the pitman arm and do the same thing, it's easier to pick up, less of a moment with a shorter arm.


In the steering system that weight is the force of the components pushing back against the pitman arm.


As far as the amount you turn the wheel, look at the arcs each arm would trace. The longer arm traces a bigger arc, bigger arc=more linear movement=less input at the wheel to get the same turning circle as a shortened arm.
 
Ryan I see your point about lifting a weight easier with a shorter arm but your not lifting a weight. You are using a fulcrum. Think crow bar. The longer the crow bar the less effort will be needed for the same force.
 
Ryan. On second thought I think you are right. I said it backwards. Sorry for my old brain fart.
 
I should have said physics tells me that with a shorter arm turning the steering wheel will be easier but you will have to turn the steering wheel more to get the same result.
 
So my question is after reading these threads is it worth it to change the arm, or is it personal preference?
 
Yes, you are using a fulcrum which is the axis of the sector shaft. You are applying the force to the teeth of the sector in order to move the load which is the entire steering system attached to the end of the pitman arm.


To lessen the force needed to move that load you can do one of two things to the system. First, you could lengthen the teeth of the sector and push on them, moving the force away from the fulcrum. A longer lever on that side means less effort. However this is basically impossible to do. Second, you can move the load closer to the fulcrum which is what the shortened pitman arm does.



Think of sitting on a seesaw in a fixed position and a big guy gets on the other end. If he sits all the way on the other end you might be stuck up in the air but if he moves closer to the pivot you'll eventually be able to balance the seesaw, he effectively gets lighter.


Edit: wmws, you've got it now. I'll leave this post here in case it helps someone else understand this down the road.
 
I have had the shortened arm on my Town Sedan for years and have not thought too much about it... until recently when I drove a friends Town Sedan and I couldn't believe how hard it was to turn. Maybe other things contributed to it being harder, I don't know. But the car is in good shape overall and steered OK, just harder..


Terry said:
I like mine (3) ! and I have noticed no reduction in turning radius. If a steering wheel is turned lock to lock the wheels are still turned the same amount.
Terry
Click to expand...

I agree with Terry. I have noticed no reduction in turning radius.

I do remember in the past some with '28-29 car complaining the steering wheel was not 'clocked' correctly'. At one time someone was selling an adjustable drag link?
 
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wmws said:
Ryan I see your point about lifting a weight easier with a shorter arm but your not lifting a weight. You are using a fulcrum. Think crow bar. The longer the crow bar the less effort will be needed for the same force.
Click to expand...

Not necessarily! It depends on the placement of the fulcrum. Put the crowbar under a heavy weight with a block of wood 6" from the "handle" end and try to lift the weight. Now put the block 3" from the weight and try again.
Or think of the pitman arm and the steering arm as two teeth on two gears (one each, such as a 4 to 1 ring and pinion). When you put power to the pinion (short lever), the ring gear (long lever) multiplies power at the axle shaft about 4 times, but the pinion travels (rotates) 4 times further.
 
I am glad with everything I read about my questions. I just ordered a Shortened Pitman Arm.
It will be installed in my 1929Phaeton

Thank You ALL for the useful Info.
 
I tried to upload a picture of my 35A in the "Quick Reply". Probably didn't work....
So another attempt.
 

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I fitted a shortened pitman arm shortened by 2" and it certainly reduced steering effort but increased the amount one had to turn the wheel.
As I could only get full lock on one side, I fitted an adjustable drag link to get the steering wheel centred and full lock on both sides.
In the end, I returned to the original pitman arm, but all steering components have been restored to original specs, it has an aluminium radiator (less weight) and the engine set back 4" (Also less weight on the front axle) so the completely original steering steers beautifully.
 
On my '29 the steering stops are at the axles, not inside the box. Kind of threw me for a loop when tinkering with the wheel center position.
 
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