Full fendered model A Gasser build thread

Neither the height of the car or the upwards angle of the draglink as single factors will cause bumpsteer. As long as the arch that the wishbones travel on doesn't bind with the arch that the draglink travels on, there's no bumpsteer.

Adjustments can be made at the spindle end, by offsetting the height of the slingshot arm, to make sure that the both the wishbone and draglink tavel along the same arch.

...ie...if the draglink and wishbone are the same length, they have to be parallell to each other....most draglinks are shorter, so they actually have to be angled upwards a bit to put them both on the same travel arch to eliminate bumpsteer with push/pull steering.

 

Correct, except that ideally you would wan't the tie rods on the spindle and pitman arm and the pivot point of the radius rod all in line as Ford made them. It also helps to have them as close to the same length as possible (drag link and radius rod). As far as the two being parallel, that works best with 4 bars since the spindle rocks with up and down movement and keeps in sync with the drag link. A radius rod/hairpin swings the spindle back slightly with travel and works best with the original Ford geometry.

Here's a lame ass drawing I did for another thread that demonstrates how different setups (mainly cowl steering) can create conflicting arcs, which can cause bump steer.

 

And as falcongeorge was trying to point out, with the two issues combined, although exaggerated in my illustration, it would somewhat resemble the "old" setup shown.

 

I do have to agree with Warpspeed on the rearend i'm afraid.
There is a guy in england with the same setup but the bars are shorter and when he drives up a high kerb you can see one wheel virtually off the ground

 

You guys sure are giving Trad27 a lot to consider. I talked to him about bumpsteer based off of Tex Smiths chassis book I borrowed from him. I figure its his truck he is building it his way and he fixed issues as they came along with his model T he built a couple years ago now and its a great driver, so he'll correct stuff as it presents itself. You guys are being an awesome help with voicing concerns before its fully together.-Weeks

 

I was not wide enough awake to spot the bump steer issue in the photograph, but it is the type of problem that becomes more and more difficult to fix as the whole project draws nearer to completion.

It just requires some very clear thinking and planning early on when laying out the steering and suspension geometry.

I hope all this is taken as the positive helpful advice it is intended to be, rather than any criticism of what is a truly excellent build.

Some of the well known problems many of us hot rod guys have, such as death wobble, bump steer, and broken parts can sometimes take years of utter frustration to work around.
While having to go back and make some fairly major changes at the build stage can be a real annoyance, it is always a lot easier to do during the build than once the car is complete, painted, and on the road.

 

My thoughts as well.

 

Any updates? New pics? I am really interested in this build.

 

Cool, nice craftsmanship, keep posting.

 

I have no clue if this would help on this setup...

but a customer of mine has an '03 Dodge 2500, with ladder bars.. they have shackle mounts at the front, and are solid in the back.. with a stabalizer bar..

would something along those lines work for this set up?

I don't have much experience with early ford type suspension.. so just wondering.

 

Good point, I was thinking about heating and bending the steering arm up to get the drag link at a better angle. Would about two or three inches higher be enough to help the problem? I figure I could raise it more but then I think it would bring the pivot too close to the spindle and mess with the ratio. I am also running a steering damner, I know people say it is just a bandaid but will it help with bumb steer at all.

 

Steering dampners are mainly to help prevent wobble and as far as the steering arm thing goes I'll have to study the pics again and get back with ya.

 

A steering damper will not stop the front wheels from steering themselves over every dip and bump in the road.

You need to see the problem with your own eyes and get the full grasp of what is actually happening. Hundreds of words from us may only confuse things even further.

Make up a rough temporary linkage between the pitman arm on your steering box, and the steering arm on your front knuckle.
Lock the steering shaft solid. Remove your front spring, and jack the car chassis up and down with the wheels sitting on the ground, and watch what the front wheels do.

Ideally both the front wheels should both point dead ahead over the full range of front suspension movement.
It ain't easy !!
But try as hard as you can to get this right, it will be well worth whatever effort you can put into it.

 

Looked at the current setup and raising the steering arm on the spindle will help, still a bit away from ideal. You may be able to get away with it, I've seen cowl steering that was more off. Never driven one with it though. Speaking of cowl steering, I'm pretty sure the Mopar boxes they use might work out with a bracket change? The pitman arm goes down and it has a long snout to get past the frame.

Hope I'm not bumming you out, if it makes it any better, this thread will probably help other guys out in the future as they try doing a similar build. Keep on truckin'

In case you're interested, I cleaned up my guestimation of your front end with a sharpie before it gets tossed. Sorry I don't have much for computer skills.

 

I was going to suggest using a "reverse" steering box, with a downward pointing pitman arm. That would be a huge step forwards, as well as looking a lot neater.

Not being an American, I have no idea what to suggest using or what you guys have available over there that is most suitable.

Don't laugh, but it is remarkably easy to fit an unknown steering box off something, and end up with the front wheels pointing left, when you turn the steering right.

 

The easiest to come across would probably be a forties or early fifties ford pickup box...F1...

Mounted on the inside of the framerail just like the original Model A box, pitman arm points down, minor adjustments made at the slingshot arm at the spindle and Boob's are your uncle.

But, if you really want to leave it the way you got it...it might take more adjusting up front...but it's gotta end up like this....

If you continue an imginary line straight off with the draglink...the red line in this poor and really small illustration....it should line up right on the centre of the pivot point at the back end of your wishbones (the heim joints you're using).

The green thing is your pitman arm and that circle attached to the green thing is where the tierod end attaches to the pitman arm.
You might have to bend that steering arm at the spindle wayyyyy up...so if it has to go grossly high, go with a different box.

 

Rember that putting a double bend in that slingshot arm or whatever you're using, is going to shorten its overall length, pulling your draglink closer to your drivers side tire. Might create some steering clearance issues, so just be-ware of the bi-product of bending the arm. I'd mock up a piece of flatbar first, easy to bend, then you can see exactly how everything is looking first...when you're sure everything's good to go, make your slingshot the same as the flat bar.

 

My head hurts, I was reading a reallllly cool build thread and ended up in a trans-continent chassis debate. Plenty of valid points, all because people care about safety. Now, show me more progress pics! Killer project, cant wait to see more. Already have stolen a few ideas for my next project.

 

Yeah X2, even though I'm responsible for most of the extra text! haha

I do wanna see pics...I love model A pickups and I'm building one right now...custom 29 body, fenderless, 32 rails.

 

Sounds very cool, dont see very many '29 pickups on '32 rails I would love to see some pics. I am at a stand still right now just trying to think it all out and change what I need to change before moving forward. The best fix I can come up with , feel free to yay or nay or input, is getting 11* rod ends on the rear end side of the ladder bars to kick the end inboard and make anouther tube crossmember that doubles as a driveshaft loop. Kills two birds with one stone as I was planing on putting a loop on a piece of 1X2 layed flat already welded to the structure of the bed but would feel better if it was solid on the frame.
As for steering I think F1 is my best and less hassle bet. Just some thoughts I have please give pros or cons. Would it be better if I switch out the front of the ladder bars from hiems to bushing rod ends like on the rear end side along with having them more inboard? I think they will handle a little bit more flex and missalighnment than hiems. Thanks for the help. I take critisism very well if it is for the better so keep it coming.

 

That sounds like a splendid plan. It has been done that way many times before, and it will work great. A good solution !

Compliant bushings are always better for a road car, because they are silent and do not wear like metal to metal heims.
My experience of heim joins is they run dry, wear rapidly and then rattle. Nobody cares about suspension noises on a race car, but it will make your Rod sound like junk after only a very few street miles once the heims loosen up.
My own preference is for standard automotive rubber type bushings wherever possible, and if you need a really stiff no rattle suspension joint, use a tie rod end ball joint. The standard automotive stuff will last forever and will give no trouble.

 

Trad27, when you say that you plan on using 11 degree rod ends...do you actually mean 11 degree offset eurothane adjuster ends? the same as the standard 4-link ends, only offset? If that's what you mean, then yeah that sounds like a plan. But don't use rod end/heim joints at the rearend mounts.

You could use a high quality chromolly heim joint/rod end at the frame mount end.

http://www.streetrodderweb.com/tech/0902sr_building_hot_rod_rear_suspension/photo_07.html
That article could shine some inspiration on your task....that's a rolling bones rear suspension setup....using heim joints/rod ends at the frame mounts....their setup is solid bolted up at the rear, but if you use eurothane bushing ends at the rear...you'll be fine...

The picture attached is from the same article...shows how the ladder bars are mounted about halfway between straight and meeting in the middle...far as I know there's been no issues with that setup.

-Steve

 

Awesome build thread! I like where you're going with this, keep up the good work!

 

Here is a pic of a nice one I snapped today at the GNRS.

 

Everyone needs an update bud..... its coming together very nicely.-Weeks

 

As far as i can see the reason the ladder bars are laid over is for clearance, You can see where the crossmember has been clearanced for the ladder bars.

 

I have posted this info before but its been a while........easiest bump steer test(if your front is togather and will bounce some)
1 Point wheels straight ahead
2 Put a small piece of tape on the top of your steering wheel
3 Go to front of car(couple buddies weight will help) and bounce car

if tape does not move side to side, then no bump steer in your system. If it moves a little.......a little bump steer......maybe normal. If it moves a lot this would indicate very uncomfortable driving on a bumpy road. The more the tape moves the whiter your knuckles will be on bumpy or uneven roads. So a bump steer simple test for any hot rod. Steve

 

No it won't.
Bounce the car, and BOTH front wheels can toe in and out together creating massive bump steer.
The steering wheel will not necessarily move at all if bump steer is exactly equal on both sides.

 

Glad you like it.

Terry

 

Yeah, I was trying to focus on the fact that they used heim joints on the frame mount end, and instead doing the straight ahead ladder bar thing or having the ladder bars almost meet in the middle of the frame....these guys were somewhere in the middle.