MTFCA Forum

Working on a friend's speedster, 4" dropped axle, lowered spindles, reversed spindle arms (for clearance), new pitman arm, all spindle bolts, tie rod bolts & front bearings all snug - problem is it's quite squirrely/darty at anything where over 20 mph. Will verify drag link length but this has me scratching my head ! 30" tires with 5-1 upper gears.

What tread is on the front tires?

Not much left - new tires on order. Toe in at near 1/4". Axle rake good.

Good day,
I may be misunderstanding your description but, swapping your spindle arms will mess up the ackerman. Causing the outside wheel to turn in into a turn at a greater rate than the inside wheel.
Short of that I assume your toe in and caster are within reasonable numbers.
Pictures may be helpful.
Have a good T day.

The spindle arms were swapped - they both are turned down instead of up as they would be normally - I'm familiar with the Ackerman principle as I did some "fancy" steering geometry on my Racer.

RajoRacer wrote: ↑

Sat Jul 06, 2024 9:42 am

Not much left - new tires on order. Toe in at near 1/4". Axle rake good.

What's the angle of axle rake. Stock cant is about 3/8". 6 degrees, I recall.
Increasing will make for better stability @ higher speeds.
My best freeway flier has a 5/8" rake.
I presume you have grabbed both wheels from the front pulling together & pushing apart looking for hidden slop. in the system.
You checked for loose wheel bearings/races?

Swapping the spindle arms won't affect ackerman.

Steve, when you say lowered spindles do you mean '26-'27 spindles?

How about the spring perches? Are they swapped?

I run a standard T axle with suicide laurel brackets, swapped spindle arms on '26-27 spindles on my speedster.

Ye - '26-'27 spindles - good rake/tilt on axle - more than stock. I'm waiting to hear from my friend/owner to verify if this is a new problem or always has been squirrely - this will be his 4th set of tires so I'm assuming it has been a problem - he built the car up quite some time ago. I replaced a short pin for a long one in the upper gear case for the stop to function - might pull it apart again to verify which slot - long or short for the stop - it's got 5-1 gears but I'm waiting to hear back regarding what steering column was used ?

I tightened up the spindle bolts, tie rod bolts & wheel bearings, John.

Steve- try reducing the toe-in. The 1/4" might be a bit too much. That much toe in will wear tires out real quick. I would try 1/8" to start. As John mentioned above, how much caster do you have? More us usually better than not enough.

Thanks fellas - I'll re-evaluate the situation - I took it out for a spin yesterday & scared the bejesus out myself !!!

Reverse caster will make any car into a carnival thrill ride. Camber and toe-in are related. More camber requires more toe-in, I think, and less camber needs less toe-in.
Long spring shackles can allow the axle to shift left and right too much, which will cause unstable steering.

A very short drag link or cross link can make a vehicle self-steer, or bump steer.

RajoRacer wrote: ↑

Sat Jul 06, 2024 12:48 pm

Thanks fellas - I'll re-evaluate the situation - I took it out for a spin yesterday & scared the bejesus out myself !!!

Steve, any chance it could use a Panhard Bar on it? We had a 'gow job' in the shop that was a white-knuckle ride that darted every which way. One of the main things we did to correct it was to install a Panhard bar to keep the axle under the front of the car. Maybe you could do something similar??

It was also suggested to split the front radius rod and/or increase the rake more.

RajoRacer wrote: ↑

Sat Jul 06, 2024 4:34 pm

It was also suggested to split the front radius rod and/or increase the rake more.

Machine a block of aluminum and use a 1" ballnose mill to create a recess for the front radius rod (wishbone) ball (-the topside of the ball) to fit into. Slip the alum. block over the studs under the pan and install the lower cap with the radius rod ball sandwiched. Go for a test drive and see if any improvement. Pushing down on the back of the radius rod will effectively give more caster w/o needing to split the wishbone or fab brackets.

One other option is to mount a GoPro camera facing towards the front end where you can see exactly what is going on as it is being driven. Is the taper on the Pitman arm loose on the steering shaft? Is the Drag Link rubbing or binding on something? A camera showing what is going on can likely help you isolate this. I know you have got to b at your wits end as this really shouldn't be that complicated. You'll get it.

If you reduced camber to make the front wheels more straight, then the distance of the tires on the road has spread and that does affect Ackermann. However, if the go cart is all over the place on a straight path, then Ackermann isn't the issue.

With a 4" dropped axle and lowered spindles you have about 4.5"' difference between the usual spindle centreline. That is asking a lot of the original front end geometry.
On my speedster with similar mods, I had an over and under wishbone. To stop bump steer we locked one spring shackle by making a triangular bracket mounted to each bolt on the shackle and to the spring clamp bolt further inboard. It worked a treat, just like a Panhard bar but simpler. This is easily reversed if it makes no difference for you.
As suggested, more caster is better than too little.

Allan from down under.

On many vehicles, the king pins are inclined inboard at the top, and the spindle centerline may not be at 90 degrees to the centerline of the king pins. This arrangement gives the vehicle more stability. I don't know if the T is made this way, but if it is, turning the spindle knuckle upside down would affect stability by making the car want to turn instead of wanting to go straight. I would check the spindle bodies to see if the kingpin bore and the center of the spindle are at 90 degrees or not, and check if either one is bent. The late knuckles are different than the earlier ones, and they may not tolerate being reversed. I'd want 5:1 steering gears and a 17" steering wheel on a speedster. Some wood wheels are "dished", and that might affect what can be done to modify the front end. Shock absorbers add a lot of stability to a chassis. Excess friction anywhere in the steering system or the springs can make the car very difficult to handle.

Appreciate all the responses fellas - played with it a bit yesterday and noticed a bit of play in the r. r. ball - not much but enough to warrant removal that's when I found the perch nuts loose although cotter pinned. Removed r. r., cleaned all and dressed off contact areas - I'll re-assemble and take her for a spin & see what happens !

Allan - do you happen to have a photo of your remedy bracket ?

If you are referring to the cap on the large ball at the rear of the radius rod, there should be studs there with nuts on them but they are fastened with wire. Do not use cotter pins because the studs can spin loose under the crankcase. With the wire running between them they will not come loose.
Norm

RajoRacer wrote: ↑

Sun Jul 07, 2024 11:47 am

Appreciate all the responses fellas - played with it a bit yesterday and noticed a bit of play in the r. r. ball - not much but enough to warrant removal that's when I found the perch nuts loose although cotter pinned. Removed r. r., cleaned all and dressed off contact areas - I'll re-assemble and take her for a spin & see what happens !

Allan - do you happen to have a photo of your remedy bracket ?

Steve, when I was racing Speedsters and Model-A/B powered Big Car stuff with AARA and DAARA, it was common to lock the L/S eye of the spring to the shackle to keep the left spring positively located in relation to the axle. Since most of what we were running used a drag link that was perpendicular to the tie rod, it was more forgiving, -and likely stronger than a Panhard bar.

In the case of a Model-T axle where the drag link is a cross steer, as the sprung weight (frame, engine, etc.) is bouncing, what is locating the axle is the arched spring yet as the weight is applied to the spring, it flattens causing the frame crossmember & rails to move towards & away from the fixed side as bumps are incurred. Because the T pitman arm is in a fixed location on the steering shaft, it will cause the drag link to pull the R/S spindle arm causing the car to change directions. In this application, that is why I feel a Panhard Bar located in the same plane as what the Drag Link creates the most stable environment to keep the front axle under the front of the frame.

Norman Kling wrote: ↑

Sun Jul 07, 2024 9:21 pm

If you are referring to the cap on the large ball at the rear of the radius rod, there should be studs there with nuts on them but they are fastened with wire. Do not use cotter pins because the studs can spin loose under the crankcase. With the wire running between them they will not come loose.
Norm

Hey Norm, re-read what Steve said again and see if you misunderstood. I believe it was the cotters on the Perch Nuts is what he was referring to. Maybe not, -but that is the way I interpreted it.

Thanks for the additional info Brent - I appreciate it ! Norm misread my post - I kinda know where the proper place for wire & cotter pins !

No photos Steve. It was a simple 1/8" plate with three holes for the mountings. Two were to fit the U spring shackle, the third was inboard and picked up the bolt which clamps the spring clip in place. Having mapped the holes, we trimmed the plate to shape and added a series of holes to make it look a bit sexier.

Allan from down under.

Thanks Allan - going to take her out for a spin before it gets too warm here - we're not accustomed to 90 + degree heat here in the PNW !

Here is Allan's bracket, his son Anthony posted a photo of it on the old forum.

Peter, I'd forgotten that iteration of the bracket. It worked well, but to my eye, on MY speedster, it looked a little to agricultural. So I made the one I described earlier because to me it looked better and performed just as well.
There was one agricultural part on the car though,The clamping piece between the two radius rods at the pan mounting was formed from a plough share that still carried the English maker's brand. It was a period piece still intact when I discovered the axle under a mobile saw bench.

Allan from down under.

Steve, Peter's posting of that first bracket refreshed my 26 year old memory of the later model I made. There were two identical brackets to the set-up. The shackles were deleted and replaced with grade 5 bolts. the long end of the triangle was anchored by a longer spring clip bolt, the position of which can be varied to fit either the over spring bolt on early cars or the under spring bolt on later models.
I probably do have photos in one or other of the dead cell phones I can't bear to throw out, but I am not into cloud storage, indexing or cataloging.
Hope this helps.
Allan from down under.

Problem remedied - seems as though when the car was assembled 30 years ago, the fella "modified" (bent) the pitman arm a smidgen to allow clearance at the draglink - well, beings that the ball was anything but resembling a round sphere, I replaced it with Snyder's repro - I realized the clearance wasn't right so removed it again and placed them in a vice for comparison - yep, that was the culprit & the fact the front end hadn't been tightened up for quite some time - called Snyder's for information about the pitman arm and being a forging, it was relayed to me to heat and bend - steers like a new Model T - appreciate all the suggestions fellas !

RajoRacer wrote: ↑

Thu Jul 11, 2024 10:56 am

Problem remedied - seems as though when the car was assembled 30 years ago, the fella "modified" (bent) the pitman arm a smidgen to allow clearance at the draglink - well, beings that the ball was anything but resembling a round sphere, I replaced it with Snyder's repro - I realized the clearance wasn't right so removed it again and placed them in a vice for comparison - yep, that was the culprit & the fact the front end hadn't been tightened up for quite some time - called Snyder's for information about the pitman arm and being a forging, it was relayed to me to heat and bend - steers like a new Model T - appreciate all the suggestions fellas !

Not all pitman arms were the same. Lengths and angles changed several times during production of the T. That being the case, the original builder of the speedster may not have modified anything.

I realize that pitman arms changed during production BUT I have several NOS arms to compare to and it was the same length as Snyder's new one at some time in it's past - he relayed to me that there wasn't any clearance with the dropped axle, lowered spindles & reversed arms.