Duke's A Coupe Build

Here are a few shots of my 29 A Coupe build. The details are, frame built with the help of a friend, custom built hairpins on the front, home made custom hurst style mount (designed to sit the engine higher in the frame), 327 turbo 350, pete and Jakes ladder bars, rear traverse spring behind axle, buick drums and brakes. Just another home built hot rod. The car will run full fenders and will be chopped (how much not yet decided).

 

nice..

 

Love the weathered paint. Looks like your going to make it full fendered too!

 

Looks like a nice job on the frame

 

Maybe a stupid question but how was it decided on how and what geomerty to use on suspesion. I'm on that step right now, like how long to make the radious rods, where to mount on the frame, is ther a ratio of how long to make them as opposed to the wheelbase?

 

Hit up Brian Angus and check out some of his earlier posts, he answers all your question. Good Luck. P.S when you find his threads subscribe to them because there is usually something new posted to it all the time.

 

My understanding of hairpins is that long is better. You can see the length in relation to the front body mount. Location is decided by your front cross member, mounts should be equal distance from your front centerline and square, caster should be close when setting them up, lay out hairpins on the ground and make sure all adjuster are lined up before instalation (I think it was so-cal that has good instructions on this). If you don't know what you are doing, don't try to make hairpins. This is a critical part and must be made out of the right stuff with perfect welds. Good stuff is available from Pete and Jakes. I had these professionaly made to my specs. I know how to weld, but I am not certified, so I know my limits. I tack everything together and get a professional to do the final welds on all suspension parts and critical mounts. It is not expensive to do this as a good welder is quick if you have everything ready to go for them.

 

I added the rear spring today. All mounts are homemade, all tack welds will be finished later.





What do you think??

 

That's a cool project,keep up the great work. Where in BC are you?

 

I am in Vernon.

 

Thanks for the vote of confidence----. My knowledge of radius rods is that yes, longer is better. Main reason for that is that the longer a radius arm is, the less movement back and forth on the axle being guided as it swings up and down thru the arc of travel. I find that the ideal point of attachment for rear radius rods is to the crossmember that supports your transmission tailstock, or up to about 10" behind it---and the closer together you can keep the ends attached to that crossmember, then the better your suspension will work. On the front, there is one caveat to remember---If you are using a cross steer (Vega) style steering set-up, then yes, longer is better. If, on the other hand you are using a steering drag link that runs from the steering arm up to the drivers side spindle, it is wise to keep the rear attachment point of the front wishbone in line with the point where the Pitman arm attaches to the drag link, when wheels are pointing straight ahead, when viewed from the side. That way, as the front axle moves up and down thru its suspension travel, the arc described by the influence of the wishbones will be equal to the arc described by the drag link as it pivots on the end of the Pitman arm, thus minimizing bump steer.---Brian

 

Duke--You've done a very nice job there, but that long plate bracket going from the rear crossmember out to the spring scares me. It is going to throw a very high torsional moment into the rear crossmember, which could lead to weld fatigue and potential crossmember failure. Here is a suggestion---this model shows an extension to the frame (in red) that will accomplish what you want to do, and be much more strong, without throwing torsional loading into the rear crossmember.----or, you can make the red area out of smaller sized tubing and add in the 2 blue struts.---Brian

 

Thanks Brian!! That looks good. What size tubing would you recommend?

 

Something around 2" x 4" x 1/8" wall for the frame extension, and 2" x 2" x 1/8" wall for the dark blue "struts".

 

Duke---I assume you plan on using something a bit more substantial to tie the spring to the chassis than just that center bolt----Right????

 

I was planning on using U-bolts, it is just sitting on the spring right now. My original plan was to run some triangle shaped gussets to the rear cross member to the braket to make it stronger. Your design looks better. I guess I will cut it out and start again. With your design would you mount the spring with a lower plate below the spring, 4 bolts, and crush tubes in the new cross member?

Thanks

 

Yes, I would probably run a 3/8" plate on the underside and use crush tubes, so that the u-bolts pass thru the new crossmember.---And if the u-bolts are on an angle I would angle the crush tubes and let them extend about 3/8" above the top of the crossmember so that when I put nuts on they would have a square shoulder to tighten against.

 

Duke---I gave you a wrong steer by email---Sorry. If you don't want to cut off your existing spring hanger bracket, then this is the way to take a lot of the torsion out of that existing crossmember. Make up 2 peices of 2" x 4" or 2 1/2" x 6" rectangular tubing with a 3/16" wall and weld it in solid as per the model. This will take 70 percent of the torsion out of the crossmember, and you can save what you already have.---Brian

 

Thanks Brian, your picture is what I was thinking about doing. I was holding some 2X4 in there last night and it looks like it would work. Would 2X3 3/16 be strong enough ?(just asking as I don't have any 2X4 3/16...I can get some though).

Thanks for all of you help!!
Duke

 

Not to go O/T but what is crush tubes?

 

Duke---at a very minimum 2" x 4" x 3/16"---

 

Since somebody asked---If you have to bolt through a peice of rectangular tubing to attach a bracket, etcetera to it, as you tighten up the bolt, the wall of the rectangular tube will begin to collapse. You want to tighten the bolt good, but not wreck the tube, so---you burn a hole thru the rectangular tube and weld in a peice of round tubing with an inside diameter slightly larger than the bolt you want to use. Now, when you torque down a nut on the the bolt, the welded in round tube will keep the rectangular tube from "crushing". This is a favourite method used on rectangular tubing chassis.---Brian

 

why don't you just lengthen the crossmember til it reaches the spring,
and use it for what the rear crossmember is for, the spring perch?
There isn't a real need for the rearend to be protected by the frame.
TP

 

Zibo, if I was going to build another frame that is what I would do. The only reason I am not doing that now is that we built the frame on a jig so it is nice and straight. I am worried that if I try to extend the frame without putting it back in the jig that it may not be as square. The proper way would be to take it appart and put it back in the jig.

Does anyone see any negatives to building it the way that Brian and I have been discussing? Will it look a little strange?

 

Seriously, not many will ever see the frame once its under the body.
Especially if the fuel tank and floor is added.
(unless you are a shop, then you should do it right, cause its a business card,
the last thing you want to say is, "well next time i'd do it this way...")

The picture I posted up there was under a pickup bed,
so it was important for me to have an unaltered bed floor.
I think that will be the only real negative is unnecesarily losing trunk space.

However,
From BA's pic,
after you make the new diagonal pieces,
(or for that matter a frame/crossmember extension)
you could just cut out the original crossmember and the flat curved pieces.
There is no reason for them if the new pieces are done right.

tp

 

cool build! when you said you were in B.C. i figured you must be inland, the body is too nice to be from the coast and the paint wear is from okanogan sun. don't paint it it really looks good.

 

Thanks for the help guys. 55 dude, this car came from a wet belt area 1 hour North from where I am at. It is pretty good, but does have some rust. Since the picture was taken I patched both sides of the cowl and used the subframe from another cowl (there was very little left of this one). The car rusted from the inside out as it was full of wet leaves when I got it (about a foot deep). The old paint will stay while I shake the bugs out of the car, but it will get some paint one day.

 

Shit yeah, listen to Brian, he's a structural design engineer(although some "engineers", like the one here at work, are idiots!). He has put out tons of great info here and in other threads.

P.S. Please tell me you will paint it nice and shiny!

 

Well Gee, Thanks!!! (I think). And no, I'm Mechanical, not structural. Every day, I read the HAMB, and every day, I quiver all over when I see some of the advise that gets offered up. I have trouble with the fact that some people do exactly the wrong thing, and since fortunately it didn't kill them (that time)---they then offer up advise to every poor fool who has internet access, saying that this is THE CORRECT WAY.

 

I definitly appreciate Brian's advice. I picked up some 2X4 1/4 to strengthen my spring mount. Brian, would it be a good idea to add the 2x2 supports from your first design as well? Also, the spring plate I used on the bottom of my mount is 3/16, is this strong enough? I guessed that it was, as it is thicker than a stock spring mount.
Thanks