MG Sports Cars

This is the Harrison/Frigidaire A6 compressor, a common sight on GM cars from the 50's into the 80's:


Next removal of the clutch:


And finally the part I am looking for, the pulley:


The sheave of the pulley came in different diameters for different cars, some small for higher speed and more output, and some large to slow the compressor down. That's how they got away with using one pump for all applications. I need a big one.

Jim

OK I got it. It's a tractor application which makes sense. Single seat cabin, 2500 rpm operating speed, need to slow that pump down a lot. The pulley is about 6-3/4" for a 7/16" belt so there should be plenty of meat above the clutch diameter and a smooth cut across at that point should not be a problem. There is plenty of room below that for the 8 belt grooves. So now to just find one. Guess I'll be visiting the local tractor shops.

Jim

Been a lot going on since I last posted. First off, the A/C based IC system has real questionable viability. No real surprise there since Ford had to use a thermal accumulator to make theirs work. The problem is that the heat of evaporation of freon is very low, something like 1/20th of water's. Various other fluids were investigated in terms of phase change temperature, latent heat, freezing point and compatibility with the system materials and after considerable calculation and testing it has been decided that plain old gasoline at atmospheric pressure and 2 gpm flow through the evaporator is the best choice. This means that a good fuel pump will handle circulation and no draw-down and purging will be necessary. OK, that's the good news. Calculations are being checked as we speak but it looks like a workable plan and other details of the system will be described later. Cabin air will be a separate system.

Next, the damper has to be mounted before anything else can be done. So, in the following photo you'll see a balancing tool I made up from bits lying around the shop.



Assembled it looks like this:



But needs more room to rotate completely so:



Here it's mounted in the bench vise. It turns out to be very sensitive and will detect less than 1/8 turn of the screw and very minute angular changes so once dialed in I marked the keyway, drilled and inserted a pin to lock the position. The slight position error that resulted meant that I had to screw a couple of bolts into the damper hub to get back to center. I dare say that when I send the finished part to Dale for checking it should be within grams of proper balance.

So next I'll knock off the inertia ring and begin to turn the adapter out of the large blank of 1018 steel seen above the stock damper in the first shot. That's over $80 worth of round stock, just one example of why custom parts cost so much. Most of it will be whittled away to make an adaptor that will precisely fit the fluid damper to the original hub, and it will also have a ring of holes drilled in the rim of it to trigger the Ford EDIS ignition system and Megasquirt EFI. Quite a bit of work before we're at that point though.

Jim

I got the blank chucked up in the lathe, rough turned, faced, drilled, and cut one counterbore on the back side for the trigger ring. Tomorrow I will try to do some more work on it, the bore for the damper hub and the one for the pilot ring on the face of the hub. First I need to measure the amount of offset weight that is needed. This can be done by placing weights on the threaded rod at the correct distance from center until it is balanced (with the outer balance ring now removed) and then finding the mass of that weight in a common sized material such as round stock. That will tell me how much material will have to be removed to balance the adapter, which in turn will tell me how much material I will have to leave in an area where it can be selectively machined away. It would be far too easy at this point to leave excess metal in the part, but this increases rotating mass and reduces the responsiveness of the engine. Conversely it would make it idle smoother but I'm not after a smooth idle. So light weight is the goal. When completed the adapter should be as light as I can make it and still do it's job. After the bores are cut and all surfaces turned to finish size I will flip the part and turn the pilot for the fluid damper, at which point the lathe work should be done. Then comes drilling the hole patterns for the damper and hub, then trigger holes and balance/lightening holes, and final assembly and fitting. Then it goes to Dale for a final balance. By then I hope to have the pump for the IC ordered and can get back to welding.

Jim

The back side of the adapter ring is done.





Jim

You insist on making this engine porn.

Motor Porn you asked for, motor porn you shall receive. Let there be MOTOR PORN!









The attachment holes, timing holes, balance holes, v-grooves and paint are still to come but it's a pretty good look I think.

Enjoy!

Jim

Nice motor. Is it AC or DC? ;)

Now that's just getting toooo-- technical.

Jim

AC/DC.

Dirty deeds.

Done dirt cheap.

Whole Lotta Rosie!

I've now gotten all the mounting holes finished, the v grooves cut, and the timing mark as well. I trimmed a little more off the center boss so that the dampener sits flush with the outer ring. The main pulley is an 8 rib and there is an inner one which is 4 ribs and will drive the alternator, provided I can mount it short enough. I still have to drill the timing holes and mill the slot for the missing tooth (36-1) and right now it's too cold to mess with it. So no photos today, but soon. Dale said he'd just as soon have it in it's unbalanced state so I will send it that way, along with the balancing jig and the old outer balance ring just as a double check. I'll try to finish it up as soon as it warms up a bit.

On a related note, I've ordered a pump for the intercooler. I've gone around and around on this design and all the while I keep spiraling in on it. As it now stands, the working fluid is to be a minimum volume of pentane, pumped at 140 gph through a closed system with an emergency pressure relief valve vented to the fuel tank EFI return line, the pump controlled by a manifold vacuum switch and by a system pressure switch (turns on if system pressure rises). It will have temp sensors at both the IC core and at the condenser and a system pressure gage. The condenser will be a standard A/C condenser, most likely identical to the one that will be used for cabin air.

A possible alternative was to use ammonia as the working fluid and a compressor but I doubt compressor volume would be adequate. However I'm still looking into that as a possibility. The volume of fluid required is about 1/4 of what is needed for pentane but it has to be pumped as a vapor rather than as a liquid due to the pressures involved, largely offsetting ammonia's higher thermal efficiency.

Nothing more yet on the intake as that work has been held up by the dampener and it's relationship to the blower drive pulley but that will be resumed soon. The alternator will need to be as short (front to back) as possible and I'll be looking into the possibility of newer candidates for that as soon as I can. The diameter isn't that much of an issue.

JB

More motor porn for you!



Above is the set-up I had to cobble together to mill the timing holes (and one slot) in the rim of the damper adapter. Precise, tedious work but a good result.



And here is the sensor mounted to the timing cover using the fuel pump location. The mount is still a bit clunky and I'll probably round the corners and such while the damper is away being balanced by Dale.



And here it is assembled. Everything matches up well other then the belt location for the alternator but I'm not done with that and have a couple of ideas yet, if nothing else just move it outboard of the head.

If you can see it, the slot (missing tooth) is at approximately 60* before the sensor. It is actually farther than that since the EDIS will trigger on the leading edge of the hole, but a minimum of 60* will allow the EDIS to advance correctly and the extra can be accounted for in the MegaSquirt timing set-up to put it dead on the money.

And for a (modest?) fee you could have one too! ;-)

JB

Really nice work, Jim!

"And for a (modest?) fee you could have one too! ;-) "

Modest fee? You must really work cheap!

Sometimes Carl, sometimes. ;-)

JB

Jim, nice B&D LED work light. They do well and can serve in an emergency as a reading light. (if we can read) . You do some GOOD work!

Thanks Kelly. Steve D gave me that light. I guess he got tired of the sorry pieces I was trying to use. It really does work great and I use it more now than probably all the rest put together.

Anyway, for your viewing pleasure, I've been a bit busy of late:









As you can see I've got the box attached to the intake and the top plate mostly completed. Still have to add the sneeze valve at the rear and then it can be welded on.

JB

Boy, You have been busy!