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  #801  
Old 02-08-2020, 08:59 PM
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Originally Posted by SuperBuickGuy View Post
.................

Quick question. On the aluminum LCA crossmember, I'm trying to see what Chevrolet did. Do the LCAs bolt/tighten directly against the aluminum "tabs", or are there any steel washers between the LCA bushings and the aluminum tabs?

I'm getting nearer to fabricating version 2.0 (aluminum) of my LCA crossmember, and I'm assuming I'll need washer clearance in the pocket where the LCA bushing reside, unless there's a reason I don't need/want steel washers in there.

Thanks.
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  #802  
Old 02-09-2020, 02:29 AM
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[quote=69427;133008]
Quote:
Originally Posted by SuperBuickGuy View Post
.................


Quick question. On the aluminum LCA crossmember, I'm trying to see what Chevrolet did. Do the LCAs bolt/tighten directly against the aluminum "tabs", or are there any steel washers between the LCA bushings and the aluminum tabs?

I'm getting nearer to fabricating version 2.0 (aluminum) of my LCA crossmember, and I'm assuming I'll need washer clearance in the pocket where the LCA bushing reside, unless there's a reason I don't need/want steel washers in there.


Thanks.
My opinion - Mixed metals -- Never a great idea. Bronze washer if you want some semi-active lube maybe - but I'd tend to stay away from steel in either of these locations on the AL setup.:


I know we get "stuck" on the ball joint to AL upright and the ball joint to LCA - but you can use some anti-seize to limit the mixed metal interaction - corrosion - etc. Same with the steel washers if that is all you have. You are dong some very nice work there -- Really inspiring!

BTW - that is something folks often forget about steel and carbon fiber - if not isolated appropriately - you might be making a battery! Just add a little winter salt on the road - a bit of water - Voila! Cathodic/galvanic corrosion.

Cheers - Jim
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  #803  
Old 02-10-2020, 06:06 PM
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Quote:
Originally Posted by 69427 View Post
Quote:
Originally Posted by SuperBuickGuy View Post
.................

Quick question. On the aluminum LCA crossmember, I'm trying to see what Chevrolet did. Do the LCAs bolt/tighten directly against the aluminum "tabs", or are there any steel washers between the LCA bushings and the aluminum tabs?

I'm getting nearer to fabricating version 2.0 (aluminum) of my LCA crossmember, and I'm assuming I'll need washer clearance in the pocket where the LCA bushing reside, unless there's a reason I don't need/want steel washers in there.

Thanks.

The lower control arm are attached via GM cam bolts - that is how you adjust the camber and caster. There is a steel tube (at least, presume steel but I never tested it) that keeps the bolt from crushing the rubber bushing which keeps it from the arm. The cam is steel on cast aluminum.

The upper arms are forged aluminum, however the inner sleeve is steel, as are the tabs and the bolts are steel as well. The bolts go through steel tabs that are floating in rubber in the arm itself

To the bottom arm adjustment - I presume GM knew what they were doing - and as these parts had 100k on them and there is no corrosion - I can only presume that the alloy is important here.... and in my experience some kinds of aluminum are far more susceptible to galvanic corrosion then other alloys.

In the boating world, it's stainless steel/aluminum that makes the aluminum the anode to stainless steel.... regular steel? not my in my experience. There are 12 points where they touch, 8 of which were GM-designed.

Good question - I'll give a qualified "I dunno" but with the caveat that this is why I kept it all GM, I think GM's QC is world class

and of course, I can't even imagine trying to drive this car in a situation where salt is on the road, I can't get it up my driveway if the gravel is even slightly moist. Thankfully, I'm not GM and I'm not building my cars to protect the darwin end of the gene pool.
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  #804  
Old 02-10-2020, 06:12 PM
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[quote=phantomjock;133009]
Quote:
Originally Posted by 69427 View Post
Quote:
Originally Posted by SuperBuickGuy View Post
.................


Quick question. On the aluminum LCA crossmember, I'm trying to see what Chevrolet did. Do the LCAs bolt/tighten directly against the aluminum "tabs", or are there any steel washers between the LCA bushings and the aluminum tabs?

I'm getting nearer to fabricating version 2.0 (aluminum) of my LCA crossmember, and I'm assuming I'll need washer clearance in the pocket where the LCA bushing reside, unless there's a reason I don't need/want steel washers in there.


Thanks.
My opinion - Mixed metals -- Never a great idea. Bronze washer if you want some semi-active lube maybe - but I'd tend to stay away from steel in either of these locations on the AL setup.:


I know we get "stuck" on the ball joint to AL upright and the ball joint to LCA - but you can use some anti-seize to limit the mixed metal interaction - corrosion - etc. Same with the steel washers if that is all you have. You are dong some very nice work there -- Really inspiring!

BTW - that is something folks often forget about steel and carbon fiber - if not isolated appropriately - you might be making a battery! Just add a little winter salt on the road - a bit of water - Voila! Cathodic/galvanic corrosion.

Cheers - Jim
that upper circle is steel on steel - the cross shaft is rubber encased so there isn't typically aluminum/steel contact.

the bottom one is how GM designed it the cross member is cast aluminum - there isn't any galvanic corrosion...

inside the ball joint housing/control arm there wasn't corrosion either - if that is because there is no airspace or because there was no electric current since the entire front suspension is rubber-mount-isolated... I dunno.

good conversation though because I was considering grounding the engine to the cross member - now I know why I won't.

I've been tempted to move the battery to the front of the car to reduce stray voltage... now I'm pretty sure I will and use an ultralight battery so the penalty is negligible.
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  #805  
Old 02-10-2020, 06:46 PM
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69427 69427 is offline
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Quote:
Originally Posted by SuperBuickGuy View Post
Quote:
Originally Posted by 69427 View Post
Quote:
Originally Posted by SuperBuickGuy View Post
.................

Quick question. On the aluminum LCA crossmember, I'm trying to see what Chevrolet did. Do the LCAs bolt/tighten directly against the aluminum "tabs", or are there any steel washers between the LCA bushings and the aluminum tabs?

I'm getting nearer to fabricating version 2.0 (aluminum) of my LCA crossmember, and I'm assuming I'll need washer clearance in the pocket where the LCA bushing reside, unless there's a reason I don't need/want steel washers in there.

Thanks.

The lower control arm are attached via GM cam bolts - that is how you adjust the camber and caster. There is a steel tube (at least, presume steel but I never tested it) that keeps the bolt from crushing the rubber bushing which keeps it from the arm. The cam is steel on cast aluminum.

The upper arms are forged aluminum, however the inner sleeve is steel, as are the tabs and the bolts are steel as well. The bolts go through steel tabs that are floating in rubber in the arm itself

To the bottom arm adjustment - I presume GM knew what they were doing - and as these parts had 100k on them and there is no corrosion - I can only presume that the alloy is important here.... and in my experience some kinds of aluminum are far more susceptible to galvanic corrosion then other alloys.

In the boating world, it's stainless steel/aluminum that makes the aluminum the anode to stainless steel.... regular steel? not my in my experience. There are 12 points where they touch, 8 of which were GM-designed.

Good question - I'll give a qualified "I dunno" but with the caveat that this is why I kept it all GM, I think GM's QC is world class

and of course, I can't even imagine trying to drive this car in a situation where salt is on the road, I can't get it up my driveway if the gravel is even slightly moist. Thankfully, I'm not GM and I'm not building my cars to protect the darwin end of the gene pool.
I appreciate the reply. I'm running a similar material front suspension (C4), but with a steel custom crossmember (similar material as C4 crossmember). With the future change to an aluminum crossmember I was wondering if the LCA steel bushings chew into the aluminum when the pivot bolt/nut is tightened. I never worried about it with the present steel crossmember, but with a softer aluminum piece it's gotten me curious.

Keep us updated on what lightweight battery you end up with. I've been looking to put one in my car (currently using a 16# lead/acid battery), but I haven't been able to get a decent reply from the lithium battery suppliers on which of their batteries will crank over a big block without having a battery weight damn close to what I'm already running, which makes for a damn high $/# expense when trying to take additional weight off the car.
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  #806  
Old 02-11-2020, 12:45 AM
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I never worried about it with the present steel crossmember, but with a softer aluminum piece it's gotten me curious.
tightening the suspension when it's on the ground is important for that very reason - the bushing should never rotate on the bolt.

The C5 suspension - the upper arm rubber bushing will hold the entire suspension up due to its resistance (unless torn, of course). That lower bushing... there is a problem that the racers note with the C5, that bolt doesn't hold tight enough to keep it from rotating and changing the alignment. once this is done, I'm pinning (drill a hole and run a screw in place) to help hold the alignment). If that doesn't work, I'll replace them with threaded heims and then block the cam in place like they do on C3 rear suspensions when you change the lower arm with an adjustable one.
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