Drag link ingenuity or bad idea????

[kelseydum]

Ok, I have a curious question. I have never seen a drag link ran like this, but when pondering how I could possibly cure my problem of running my drag link at an angle. I know you are supposed to get the drag link as parallel to the radius rods as possible, but I've seen several people running their drag link at an angle which in turn can cause bump steer ( if I understand correctly). For some people it seems to be okay and others have problems.

My question is can you run an "L" drag link?... Meaning can you add a 90 degree angle (with a brace) to help solve the problem? I photoshopped a pic to show what I'm talking about. Now maybe the brace doesn't need to be as long as the one photoshopped, but you get the idea I'm coming up with. Being a new guy to this I mentioned this to my mentor and he seemed intrigued as he has never seen this done before... and wondering if it would work. I was wanting to get some feedback from some of you pro's.

... Well what do you think?

before...

after...

 

[bob w]

Kelsey, Look up the thread titled "Avoiding Bump Steer" in the technical section. With hairpins the drag link should not be parallel. There is a diagram showing the ideal arangement.

 

[bob w]

Here's the diagram from an old rod magazine.

 

[kelseydum]

So maybe I can flip the pitman arm upside down as long as at the furthest point it doesn't break the plane of upward arc? If I understand correctly once the pitman arm start to break a certain plane then it will start to steer in reverse.

... but does the question in hand effect the steering. If I were to make the drag link angled correctly WITH the elbow would it still work?

 

[Sniper]

I'm not an engineer, and this is just my personal opinion. But I don't see a change in the outcome of any sort from the before to the after. The reason being, from point 'A' to point 'B' in both cases has remained the same, regardless of the shape of the draglink. There would only be a change of outcome if either point 'A', or point 'B' where moved. Just as a side note, I've had a few "Hey, I know" moments, that were proven good and/or bad with something as simple as a Meccano set. I've 'built' the idea and tried it out. Some ideas have worked, a lot haven't, and some were modified and found to be possible. The point is, it cost nothing but a little time on my part. My Meccano 'Toys' as my wife likes to call it, has saved my butt more than once. And, I would like to add, congrats, to thinking outside the box as they say. Sniper

 

[Blue Eyed Devil]

Creative thinking yes, but I don't think it will work. That arrangement looks like it may bind, and it is also not very attractive. You would be much better off using a box with a pitman arm that points down, such as an F-1, F-100, reversed Corvair, early Econoline, etc. They are plentiful, easy to adapt and would get you much closer to an ideal setup as shown in the diagram. It would be also be safer and look a lot cleaner than what you are proposing. I am sure you could trade or sell your Mustang box and come out close to even...

 

[kelseydum]

I really haven't spent any money on this setup yet... just seeing if it will work. Can I flip the pitman arm upside down? Besides what's attractive about a single bar, that's why I chose the hairpins instead of splitting a wishbone... just personal opinion. I'll find a way to dress it up and make it look good. I just need to know if it will work.

 

[EnglishBob]

to turn the pitman arm upside down you'd need to reverse the inner workings of the steering box.
probably cheaper and easier to trade it for a mustang/f1 or similar box

 

[Sniper]

I really haven't spent any money on this setup yet... just seeing if it will work. Can I flip the pitman arm upside down? /QUOTE]

No, flipping the arm would reverse the steering. Sniper

 

[Blue Eyed Devil]

I really haven't spent any money on this setup yet... just seeing if it will work. Can I flip the pitman arm upside down? Besides what's attractive about a single bar, that's why I chose the hairpins instead of splitting a wishbone... just personal opinion. I'll find a way to dress it up and make it look good. I just need to know if it will work.

Ok... forget that I said it won't be attractive and focus on the fact that it will bind. With the tie rod end on the bottom of the steering arm and your pitman arm swinging upward in it's arc, it is going to bind there and put stress on the whole assemby. I respect your opinion of what you think looks good, but this is a safety issue. Steering is not a place to gamble. Like I said it's not a big deal to get a box that will work properly with your setup. It's a simple solution - better to correct it sooner than later.

You can't flip the pitman arm around because it will reverse the steering. Unless you are building a boat that won't work out so well...

 

[Willowbilly3]

No, do not do that. I had an old T bucket they had done it to and it is not good. Besides, the effectual angle is the straight line from point to point. Read the bumpsteer thread. It is probably the best write on bumpsteer anywhere on the internet.

 

[kelseydum]

Thanks for the info. I think I get it now. I may try to reverse the box.

 

[adam]

The main cause of bumpsteer in your situation is simply because the radius rods are a different length than your drag link. As the Axle goes up & down in a big arc due to the long radius rods, the tighter arc of the shorter drag link pulls the steering arm, turning the wheels. To effectively eliminate the bumpsteer, you would have to have the radius rods' frame mount & drag link/pitman arm connection @ the same location (front to rear). The difference in the angle of the drag link compared to the radius rods doesn't really make a lot of difference, unless it's a lot. Also, in a 4-bar system (as compared to a wishbone setup), you will never totally eliminate the bumpsteer because the caster doesn't change as the axle swings in an arc-even with the drag link the same length & angle as the radius rods. That would be so minute that it would be practically imperceptible though.

I race a sprint car, and we have the same steering/front suspension scenario, only we have a long drag link, with front radius rods that are less than half that long. In the picture, you can see we have only one rod on the left side, but we have two on the right side. That's because with the severe amount of side to side body roll (both ways) that we sometimes get, a true 4-bar will bind up.

 

[kelseydum]

I think reversing the box will give me a great pitman arm placement. It doesn't seem too difficult or time consuming.

Thanks for the responses and help. I love learning this stuff. If it were all easy it wouldn't be any fun.