Coilover lower mount on A frame fab question

Started by socorob, February 16, 2012, 04:30:00 PM

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socorob

Im wanting to put coilovers on the front of my Alpine. The original front shock sits inside the coil spring but it has a straight threaded fitting at each end. The mustang II coilover I'm looking at has the same threaded rod at the top but an eyelet for a thru bolt at the bottom. I need to make a mount that is like this. http://m.summitracing.com/parts/SJA-SKDGEB1/media
My thinking is the make a 1/8 steel ring for under the a arm. On top of the a arm I would have to make a ring to fit inside where the spring sits to space it up to the top of the flat area of the a arm. For the 2 uprights that the lower shock bolt will go thru I was thinking about using 3/16 thick angle, welded to the spacer ring, with bolts going thru the angle, the spacer ring, the a arm and the ring under the coil bucket and sandwich everything together with 4-6 bolts. The front of my car is probably around 1200 pounds. Will 3/16 cold rolled or hot rolled angle be strong enough for this? I plan on leaving about 1/4 inch of steel over the hole in the shock bolt left on the angle. I assume most of the pressure would be pushing against it, not pulling on it. Is that a correct assumption?  I would use 375 pound springs on it.

mgb260

Moss had a how to article a while back on using Mustang II coilovers on a TR6. I think the lower mount ring you are talking about is what is used for the bottom of the tube shock in the rear of a TR6. I think Dan Blackwood did something similar.Here is a pic of Calvin's brackets:
Picture 181.jpg

socorob

http://www.britishv8.org/Articles/TR6CoiloverShocks.htm

I found this which is similar to what i wnt to do, but i have to address the bottom mount. I dont think I will have to cut the spring.

socorob

did he make those or are those part of some kit?

mgb260

The brackets are part of a kit. Calvin's thread is a sticky on the top of Triumph part of this forum.You could make brackets like that or make a  1/4" plate with oval hole and 2 bolt bar pin mount to weld on bottom A arm.(Chevy lower mount). That is what I plan on my MGB through the spring tube shock conversion.

socorob

I thought about the bar pin because it would probably make things easier, but i dont know if i trust the whole weight of the front of the car on 2 small bolts.

mgb260

Actually QA1 sells a replacement for 67-69 Camaro coilover with bar pin mount. The bar pin mount is strong enough for stock Chevy and other GM cars with shock in coil spring. I'd be more worried about the weld on  bottom plate. I would use grade 8 bolts,washers and locktite on threads.


socorob

http://www.tffn.net/phpBB3/viewtopic.php?f=11&t=21379
I may machine a round piece of thick metal to fit into the lower spring trough and weld and bolt one of the afco coilover mounts to it, something like this guy did. My bottom plate is riveted on with large rivets, and takes the coil spring on there from the factory. i will weld it all up while i have it apart.

mgb260

Robbie, Looks good. Can you grind off the rivets and bolt your new plate in those holes.

socorob

I'm going to leave the original plate in place and sandwich it with my mount. I'll also weld the plate so there's more than the rivets holding it in.

mgb260

Robbie, I like these better than the Afco ones. Evidently Jeep's and Chevy 4X4's break the bar pin loose quite often. I'll probably make some out of channel but the price with bushings and bolts is very reasonable.
http://www.4x4groupbuy.com/store/teraflex-shock-eliminator-p-6104.html

socorob

Im still trying to figure out how exactly im going to handle these bottom mounts. This is what im working with. My plan is to make a ring out of 1/8" steel to go under the a arm where the coil spring sat. It will be basically a 1" wide washer thats 5"OD, 4"ID, with 6 1/4 or 5/16 holes around it. On top of the a arm I will make a 5"OD ring out of some thick steel, and make it to fit down into where the coil spring sat, and be a solid piece about 1/8-1/4 above the bottom of the spring retainer to give me a nice flat weldable area. I would make the same 6 holes around this piece so it could all be bolted together to sandwich where the coil spring sat. What Would be easiest to do is to use 2 pieces of angle iron to drill through to mount the lower part of the shock with a 1/2" bolt going through them. This would be welded to the top round plate and each side would have 2 bolt holes, so it would bebolted thru and thru as well as welded. My question is, would 3/16 or 1/4 thick angle be sufficient for the bottom mount? I think the pressure is mainly downward, but i want to make sure it will be safe enough.
front suspension medium.JPG

mgb260

Robbie, If it was me,I would just weld the solid 1/4" top plate  all around(no bottom ring). Weld on bottom where stock opening is. Then use 3/16"(.188) square tube or channel to make a one piece bracket like I show above. Plenty strong.

en

The top pin mount on the front suspension was designed to mount the shock.
Is it strong enough to take the increased load/stress from a coil over shock?

mgbreis

Robbie, you're doing exactly what I've been daydreaming about doing on my Hillman. Any chance I could talk you into sharing specifics on the shocks and springs you're thinking of using? I have an Alpine series IV or V front suspension on my Hillman (I don't know which) and it already has a through-bolt bottom shock mount like you're trying to build. I'm not sure how it would work with a coilover though. When I was rebuilding my suspension, I seam welded the riveted top shock mount and if switching to coilovers I'd probably weld in a simple brace on the backside of the mount. There's not a lot of room but you could fit in a brace.

I'm also planning on building a frame mounted sway bar from the link that Jim provided over on the mgexperience. My experience autocrossing with the Alpine sway bar last summer was not good. Way too much body roll.

mgbreis

P.S. Robbie; as long as I'm begging, how about posting a write-up and some pics of your 4-link?