MT647 -8V-71 custom crank adaptor finished! and it fit! Woo Hoo

[bevans6]

I'm sure you will all be as pleased as I am that I finished hacking my crank to flexplate adaptor out of the crappiest machining mild steel I ever saw, and lousy surface finish aside, it fits perfectly.  For those who care, which I am sure adds up to me, the offset hole is somewhere between 3.5 and 4 degrees off of 180.  I got tired of trying to measure it, and stuck the hole in at 3.75 degrees off center.  I have no idea why I go to these lengths when I know that I am not going to get 1/4 degree accuracy on the hole with my old mill, drill chuck and drills anyway, but I can't let it go.  I figure if I try for perfect, the automatic mistakes will add up to pretty OK, which is indeed what happened.

Brian

[eagle19952]

picture please 

[lostagain]

You're going to have to drive your bus out West to show it off so we can all see it...

JC

[Dave5Cs]

I personally can't wait. JC I think we should book the next flight out and go see Brian's project completion....I have never been to Nova Sochia. Have you, LOL Kidding ya Brian...

PS Pictures???

[Oonrahnjay]

... it fits perfectly.  ...
Brian 

      Great news, Brian.  What are your tasks left to do on the overall transmission project, and what's your time line?

[chessie4905]

I've been following your endeavor with interest. Glad to see you are making headway. People don't seem to tackle projects like this these days.

[kyle4501]

Brian,
Great to hear of your success! How long before the first road trip?

We'd love to see you back down this way. Been too long.

If I ever get enough vacation . . . . . I could take some real trips!

[bevans6]

Kyle, it only looks uphill because it's north on the map.  In actuality Nova Scotia is downhill from your neck of the woods.  On average.  There is a nice hilly stretch through Maine to the Canada border at St Stephens.

I hope to be back in the shop this afternoon or tomorrow - painting the den today, wife's orders prevail.  I'll post some pictures, an update, and probably someone will say "I've got the exact MCI official parts you need to do this right, where do you want me to mail them.  No charge for a fellow bus nut!"

Brian

[luvrbus]

Brian, send me a PM on this board with your sisters address I need to get the after cooler to you before it gets lost or thrown away.The Canadian shipping is just to damn expensive   

[bevans6]

To recall what happened to get me to this point, I was having ever-worse  clutch issues with my Spicer.  I later determined that the input shaft was knackered, the clutch discs could not move to disengage, and so would drag badly.  It was never possible to easily engage first from neutral, and if the thing got hot the clutch would drag badly.  So I got a re-manufactured MT-647, and started to install it.  I got the official Allison install documents for an 8V-71 with SAE 1 bell housing, ordered the flexplate, got the SAE 1 to SAE 2 adaptor, and thought I was off to the races.  Quickly discovered the $800 flexplate that I had ordered and which could not be returned was so not the right size, MCI used a SAE 1 bell housing but a custom flywheel size (basically SAE2) so the ring gear was way too big.  There is a special flexplate made to install a MT 647 onto an MCI 8V-71, but after trying for almost 2 months I could only find one new one for $2K, and no used ones.

So I determined that a Cummins ring gear would be a very close fit, I would just have to finesse the adaptor plate to space it correctly, cut the flex plate I had down to fit, space out the transmission a little bit to get that clearance right.  I may have to machine the starter nose to move it out a bit, the Cummins ring gear is 103 teeth while the MCI ring gear is 102 teeth (same tooth profile) so the Cummins one is about .050" larger on the radius.

What I just did is step one to making this whole mess a working project.  I measured the spacer thickness I needed to put the ring gear the right distance from the starter pinion, so the starter gear will engage the ring gear correctly.  This was 0.625", so that is my crank flange adaptor thickness.  The adaptor has three registers that locate it correctly, one that slips over the crank flange, one that is a very close fit to the ID of the center hole in the flex plate so the flex plate is kept perfectly centered, and a 1.702" hole that the pilot on the MT-647 torque converter flywheel fits into.  The trick is to get all of these registers perfectly (with .002" tolerance, and zero is better) concentric to each other, and the inside face perfectly parallel to the outside face.  Doing this setup on a 1939 Southbend tool room lathe with a somewhat worn out three jaw chuck is an exercise in patience.  Doing the first side, cutting the pilots for the flexplate and boring the hole is easy, turning the work piece over and getting it re-chucked to do the second side takes a lot of finesse, measuring with dial indicators, tapping, etc.  I think it took me around 45 minutes to get it within tolerance (.002" or less).  After that you just face it off and cut the register for the crank flange to slip in to.

The crank has 8 bolt holes, two of which start life in production as locating dowels with one offset so you could only install the flywheel one way, for balance purposes I would imagine.  Somewhere along the line they started using 8 bolts, with bolts replacing the dowels but still with one offset.  I measured the offset hole as being 3.5 to 4 degrees off 180, but could not measure closer than that, so when I drilled the holes I put that offset hole 3.75 degrees offset.  That is around .008" difference between 3.5 or 4 and 3.75 degrees, so splitting the difference and drilling the hole .031" larger in diameter for bolt clearance made the whole deal work out.

Some pictures.  I don't know what order they will end up in, but there are pictures of the adaptor on crank with the 8 bolts and the scuff plate, you can see the hole and the register for the flex plate, pictures of the flex plate with the too-big ring gear and the Cummins ring gear, I think one with the adaptor sitting on it so you can see the register for the crank flange, and one of my Bridgeport, the little rotary table, and my lathe.  BP is a 1972-ish Varispeed, the lathe is an ex-Canadian Army 1939 Tool-room 16" by 60" bed.  The tool-room part is it came with all the accessories needed to make tooling for production use, as opposed to a production lathe that might not have come with a tail-stock, or collets and such.

[bevans6]

Couple more pictures..

[Oonrahnjay]

    Nice work and nice workshop.  Good luck with the rest of this project.

[buswarrior]

Great job, and as usual, a great write-up!

happy coaching!
buswarrior

[lostagain]

Amazing! I can turn wrenches. Rebuild engines with a shop manual, but this level of machining is beyond my abilities, and I don't have the tools. Remarkable! Hat off to you. I wish I was your neighbor, I could mow your lawn and shovel your snow for machine work...

JC

[MB LeMirage]

Nice Enfield, one of my favorites.
Ryan.