Front end engineering question
Thread Starter
Racer
Joined: Jul 2010
Posts: 261
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From: Manahawkin NJ
Front end engineering question
I had a cracked lower a-frame mount on the front crossmember that was crudely repaired. I remover the lower a-frame and removed the old mount and replaced it with a new one. The old one was cracked where it over hung the rear of the crossmember. The crack was between the one large bolt and the crossmember. After seeing the crack I want to beef up the a-frame mounts both upper and lower
I want to stiffen the frame with an upper spreader bar that I can fabricate myself. Are the forces on the upper a-frame putting more stress on the front or rear of the mount. It seem if I put the spreader bar centered on the cross shaft it would work as a pivot point and possibly be counter productive.
I plan gusseting the lower mount to the inside rear. It seems to me that during braking and hard cornering, the force is trying to push the rear of the a-frame inward. If I don't gusset it, I was thinking of small spreader bar mounted to the rear mounting bolts.
Any help would be greatly appreciated.
Tom
I want to stiffen the frame with an upper spreader bar that I can fabricate myself. Are the forces on the upper a-frame putting more stress on the front or rear of the mount. It seem if I put the spreader bar centered on the cross shaft it would work as a pivot point and possibly be counter productive.
I plan gusseting the lower mount to the inside rear. It seems to me that during braking and hard cornering, the force is trying to push the rear of the a-frame inward. If I don't gusset it, I was thinking of small spreader bar mounted to the rear mounting bolts.
Any help would be greatly appreciated.
Tom
Le Mans Master
Joined: Apr 2007
Posts: 7,353
Likes: 72
From: Graceland in a Not Correctly Restored Stingray
Installing a proper spreader bar between the upper "towers" and fully gusseting the A-frame mounts are both prudent chassis improvements if you're going to be leaning on it very hard. More good info here...
http://www.corvettefaq.com/c3/ChevyPower.pdf
FWIW, most upper spreader bars end up at or near the front cross shaft bolts, as is VBP's.
http://www.corvettefaq.com/c3/ChevyPower.pdf
FWIW, most upper spreader bars end up at or near the front cross shaft bolts, as is VBP's.
Last edited by TheSkunkWorks; Aug 9, 2010 at 03:14 PM.
Thread Starter
Racer
Joined: Jul 2010
Posts: 261
Likes: 0
From: Manahawkin NJ
Charlie,
Great info, thanks a lot. I just skimmed it but will read it all tonight.
Do most spreaders end of forward because it is easier that way? I was planning on reinforcing the outside of the tower and mount the spreader lower the the VBP. I was going to weld a plate under the cross shaft with the spreader going to that, instead of bolting to the cross shaft.
After reading the info you sent I think the whole plan might change.
Thanks again
Tom
Great info, thanks a lot. I just skimmed it but will read it all tonight.
Do most spreaders end of forward because it is easier that way? I was planning on reinforcing the outside of the tower and mount the spreader lower the the VBP. I was going to weld a plate under the cross shaft with the spreader going to that, instead of bolting to the cross shaft.
After reading the info you sent I think the whole plan might change.
Thanks again
Tom
Le Mans Master
Joined: Apr 2007
Posts: 7,353
Likes: 72
From: Graceland in a Not Correctly Restored Stingray
Glad to be of service. It's vintage info, but still good.
IMCO, having spreader bar level with the cross shafts looks like the best way to minimize flex, as is its intended purpose. Looks easier too. I'd recommend them to any C3 owner, but the higher are your front spring rates, the more so you need a spreader.
FWIW, my BB forced the bar right up to those front bolts. Sorry, no pics. My shark is currently in pieces, awaiting funds to finish a laundry list of additional mods and upgrades.
IMCO, having spreader bar level with the cross shafts looks like the best way to minimize flex, as is its intended purpose. Looks easier too. I'd recommend them to any C3 owner, but the higher are your front spring rates, the more so you need a spreader.
FWIW, my BB forced the bar right up to those front bolts. Sorry, no pics. My shark is currently in pieces, awaiting funds to finish a laundry list of additional mods and upgrades.
Thread Starter
Racer
Joined: Jul 2010
Posts: 261
Likes: 0
From: Manahawkin NJ
I just installed 460lbs VBP with all new poly bushings and ball joints. I had a crack to the lower passenger side a-frame mount. It looked like the lower half of the mount under the frame was twisted and then pulled back into position. The top half was separated from the frame and rewelded where ever it landed. I used a tram gauge to check squareness of the frame from every alignment hole and the frame checked out perfect (for a C-3). I then removed the lower ball joints and re-tramed from alignment holes to ball joint holes and found the passenger ball joint back 3/4 of an inch. I removed the old mount from the frame and rewelded a new mount using stock type welds and then welded the lower mount's sides the length of the mount. It seemed like it should be like that from the factory.
I was wondering if the car went over a curb or if stress damaged the lower mount? That is why I want to beef things up a little.
Tom
I was wondering if the car went over a curb or if stress damaged the lower mount? That is why I want to beef things up a little.
Tom
