Fabricating an A/C Compressor Mounting Bracket

Machine Shop
#1

In case anybody missed it, I’ve been working on swapping the engine in the silver 200SX in the automotive square. It’s pretty close to completion, it just needs some finishing work and some fabrication.

Among the list of things that need to be worked out is the A/C compresor mounting bracket. Since the car’s A/C works and the system contains a full charge of rare, expensive, and difficult to replace R12 refrigerant, I’d really like to keep the system intact and installed. However, while the original bracket will bolt onto the new engine, its position puts its tensioner pulley in contact with the crankshaft pulley. Extending the pulley mount was an idea, but the bracket is made of cast iron and I don’t believe it will take well to welding. The position it places the belt drive for the compressor is also less than optimal. (The engine uses a 3-belt design to run its accessories, and the original bracket would require the compressor to be operated on the power steering/water pump/fan drive belt, rather than its own belt, as intended by the engineers)

I’m not very skilled in the arts and sciences of metalworking, so I’m looking for some advice here. Would it be feasible to fabricate a new bracket from sheet steel? (Not really this group’s area) Alternatively, what level of cost and difficulty would I be looking at in milling a bracket from a block of some sort of metal? (Totally this group’s area)

The bracket in question is pictured in the diagram below. It bolts to the engine block in 4 places, and the A/C compressor bolts to it in 4 places. The tensioner is a screw-adjusted block that slides in a small channel and carries the pulley shaft. (Similar to the second image)

Any insights are much appreciated, as I’ve been pretty stumped on this one part of the build.

With all due respect,
Kris

#2

Milling out of aluminum is always a possibility. It first requires creating a CAD model, keeping in mind the limitations of 3D milling and our tooling package.
Can you get a smaller idler pulley (that clears the crank pulley)? Can the bracket be spaced off of the block (allowing it to clear)? Perhaps an adapter could be milled that simultaneously spaces the bracket away from the block and aligns it with the channel of the crank pulley you’d prefer to use. Without seeing it in situ I couldn’t really say.
As to cost: Billet aluminum runs approximately $2.50-$3.50/lb, and is 0.098 lb/in³. Difficulty depends on too many variables to speculate. If you had to pay someone to model and mill it I think you might opt for converting to R134A.

#3

An adapter may be the most prudent solution. I’d have to move the bracket backward and outward to get the alignment and clearance I need. I’m not all sure how much I’d need without being at the car to take measurements at the moment.

Unfortunately, the idler here is about the smallest I can reasonably get, so it does rule out trying to make the existing setup work without modification to the mounting.

I’m going to do some more research. Hopefully tomorrow I’ll be able to get the rest of the car together enough that I can even worry about the HVAC system. Maybe I’ll even have an epiphany in my sleep tonight.

#4

Having been in a frustrated, sleep deprived position before, I will risk stating the obvious. To get the car mobile you can remove the idler pulley and bolt the compressor in place. Then you can modify it at your leisure.

1 Like
#5

Without laying eyes on it, I’d be tempted to go to “heim joint adjusters”; something like this obviously in an appropriate size.
Using the existing top bolts as pivot points, attach 2 of these in the bottom holes (or is there only 1, as it appears on the picture?), and eliminate the tensioner pulley altogether.

That’s my first reaction.

My second is, could you build one from sheet metal? Yes, but it probably becomes “plate” at the thicknesses involved. I have seen plenty of “sheet” brackets, and they are usually broken…

#6

So neither a ka24de bracket or original bracket will work without modification?

#7

I already have the idler removed for clearance reasons, and intend to put it together as such for now, while it’s SNOWING IN MARCH. It’ll at least hold the compressor on.

Jast, I don’t believe that will work, due to the nature of this compressor bracket.

Brandon, that is indeed the case. The CA20E A/C compressor mounts to the bracket in a totally different fashion to the KA24DE compressor, and the CA20E bracket doesn’t align the compressor properly on the KA24DE block. And, yes, I did try mounting it to the bottom mount holes, which don’t line up exactly with the top holes. No dice.