I need to replace my model a frame front crossmember with tis one do I weld this level or is there a degree it needs to be welded at......also when cutting the crossmember loose will the front spring out or will it hold its shape long enough to weld in the new one.....Thanks
You need to make sure that the point that the spring mounts to is between about 5 to 7 degrees from level as measured with the frame rails level. This is what controls your caster on an early Ford front suspension. I usually shoot for 7 degrees. On most repro crossmembers, this is built into the spring pad itself. If your frame is in good shape, it shouldn't spring out ward. I'll ***ume that you'll be doing this with the motor and such removed, so that shouldn't be a factor. However, I would probably brace it just behind the crossmember a bit just to make sure. Just make sure to leave your self enough room to get the crossmember out.
Depends. Some have the caster stamped in, some don't. You need to determine whether there is a provision for caster built into the spring seat. Set it up on your workbench and level the ends. Now use a machinist protractor or angle finder to check the spring seat. If it's level too, there's no caster built in and you'll have to install the crossmember in on an angle. You'll get differing opinions as to how much it should be angled back, but 7º seems to be the predominant number. As for cutting the old one out, I'd secure the frame to a welding table, or at the least cross brace it before cutting. You'll probably have to trim the ends of the crossmember and "field fit" it in, so don't trust the frame to retain it's shape with no bracing. Bob
The cross member should be at 5 to 7 degrees with the frame raked or tillted at ride angle. If you are going to have the frame running down hill 5 degrees, the cross member would be set at 10 to 12 degrees. Frame rake 5 degrees plus 5 degrees for cross member equal, 5+5= 10 degrees. good luck
I don't think you got that right. To work properly, the kingpins should lean towards the rear of the car at the top by 5 to 7 degrees. This means that the underside of the crossmember where the spring sets should be lower at the rear side than at the front by that same 5 to 7 degrees. And it can be measured from the top of the framerail, without considering any potential "rubber rake" that will come from large rear and small front tires.---Brian
If you're unsure of what your final ch***is "stance" will be, you may want to consider adjustable spring perches. Lots of guys don't like them because they don't look "traditional", but they can sure take the pain out of adjusting caster if you don't get it right on the first try. Bob
The crossmember should be mounted so the spring mount is in a flat plane with the radius rod mounts. This is to get the spring 90 degrees to the center of rotation. This keeps the spring from getting in a bind. The caster is a seperate issue. I just bend the perch bolts to get the axle angled back and not bind the spring. This is really the way to do it and other methods of steeply angling the crossmember are less than correct. 30 year registered professional engineer and 50 year hot rodder.
You need to clamp the frame to some sort of JIG plate or a pair of I-Beams. Otherwise when you weld the frame it may draw up on one side and your ch***is won't be flat. It would be hard to see but it will affect the handling when your done. Scott Fab Manager Welders360
The most important thing to know is what angle/rake the frame will be at -- at actual run time. It is fairly typical for there to be a 3 - 5 degree angle toward the front on hotrod setups (***uming you're running a dropped axle in the front and big n' little tires). If you're working on just the frame (not in the car), then you'll need to account/guesstimate your running rake before you set the cross member and tack it. If you have the side rails level to the welding table or surface, then you need to combine the estimated frame rake with the caster rake for the correct angle (like 10 - 12 degrees). Many of the aftermarket cross members already have an angle build into the spring mounting pad -- all you need to do is use an angle gauge to set it up before you weld it. I'd use some heavy tubing braces and tack them in behind and in front of the cross member to hold the frame while welding -- it sure won't hurt to try to keep things from moving. Also, don't weld everything all at once - alternate back and forth to try to keep the heat and warpage down. Also, make sure you know whether the new cross member was designed for a boxed frame or not -- many are designed for boxed frames. You may need to box the front of the frame before you put in the cross-member, or it may be WAY too narrow (just know what you have before you start!). Here is a crude picture - shows a 34 frame, same deal for a Model A: Here is a picture of the angle gauge I used (Home Depot) - when I setup the rake on the jig. I had the frame rails level, then set the front cross member spring-pad rake at about 5-6 degrees tilted to the rear.
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