HM100 Tapered Shaft Fix...

Yellowhand

Yellowhand

#1
#1
Pics 1 & 2- New Tec HM100 short block bought off ebay by a fellow OldMiniBikes member...he had them ship it directly to me for machine work on the tapered crankshaft.

Pics 3 & 4- He'll be running a 3/4" torque converter driver, so I'll machine the 7/8" tapered crank down to 3/4" OD x 3" long...

Pic 5- NOT the correct way to remove a flywheel...Tec makes a tool that wraps around the flywheel, but I don't have one, so it's braced with a rod against the magnet housing.
 
Yellowhand

Yellowhand

#2
#2
Flywheels on new engines usually come off easily, and this one was no exception...the nut came off without breaking the flywheel.

The block is clamped to the bench, and an 8" puller pops the flywheel right off...

Flywheel key is gently prised out with sidecutters to get a grip on it...

Last pic is the external governor mechanism...
 
Yellowhand

Yellowhand

#3
#3
Governor arm spring is removed so the side cover will come off...

I try to keep all the small parts in a safe place while an engine is apart...

Side cover bolts removed...position of bolts was noted, since they vary in length...

Side cover was pulled off without prying on it to prevent damage to gasket surfaces...
 
Yellowhand

Yellowhand

#4
#4
This side cover gasket is new, so I'll try to re-use it by gently under-cutting any adhered areas with a razor blade during removal...

Timing marks lined up for cam removal...the HM100 has a compression release on the back lobe, so some precise alignment is needed to remove the cam without hitting a lifter with the compression release arm...

I turn the block upside down to keep the lifters in the 'up' position...

Cast iron cam...a rare sight these days...

Last pic is rod cap marking on outside lower bolt hole...if it wasn't marked, I would have marked it to make sure the rod cap goes back on the same way it was positioned before removal.
 
Yellowhand

Yellowhand

#5
#5
Rod cap removed, and crank removed after manuvering the rod out of the way...note the miniscule dipper...

Last pic is checking the tailstock center on the lathe before turning the crank...if the tailstock is off-center, the crank will be tapered, and we don't want that, so two centers are aligned in the headstock and tailstock to insure the axis is straight...
 
Yellowhand

Yellowhand

#6
#6
I put the flywheel nut back on the crank and tightened it down to use for a chuck-clamping surface...chuck jaws can damage bare threads, and won't clamp tightly to a taper, so this was the only mounting configuration possible for this size chuck...

I installed a dead rest near the rod journal and a live center on the crank end to minimize vibration...cranks spin out-of-round and vibrate badly, so they need to be turned slowly (120 rpm) and dampened if possible...

I back-cut the crank towards the side cover about 1" to shorten the shaft...

Last pic is full-length, but still 7/8" OD...
 
Yellowhand

Yellowhand

#7
#7
The crank was full-length turned to 3/4" OD (exactly 0.750") and trimmed to 3" length, then faced and bored/tapped 5/16" NF for a retaining bolt...

Pics show spotting drill and rough drill...

I put gunsmith's threads (crowning) in all the cranks I machine...the end of the crank is free-bored slightly and the threads are recessed like the rifling in the muzzle of a gun barrel...
 
Yellowhand

Yellowhand

#8
#8
First pic is the finish drill...

I hand-tapped this crank...I don't have a tapping head for this lathe, and it doesn't have a 'jog' button...tap is a CLEVELAND brand HSS 5/16" NF...extremely good quality tap...

Back-cutting on the shaft moved the driver mounting point an inch closer to the side cover...

I'll take the crank to a shop to use a vert mill to cut a 3/16" keyway...

I'll try to remember to shoot a few pics of that, and also some for re-assembly of the engine to complete this thread.
 
Yellowhand

Yellowhand

#11
#11
The first three pics are a Tec OHH55 that began as a shortblock tapered shaft from the same ebay seller as the HM100...

I bought it, machined the crank to 3/4", and finished it with parts from a blown yard sale engine...I'm 'borrowing' the clutch to test the HM100 crank after I mill it...

HM100 crank next to an OHH110 crank...both engines use the same crankshaft, even though one is a flathead and the other is an OHV...saves manufacturing money...the OHH110 is also a tapered crank engine I'm machining to 3/4"...

Last pic is the new Capps Manufacturing building...let's go inside and machine a crank...
 
Yellowhand

Yellowhand

#13
#13
My favorite mill, a new-style Bridgeport Model J with an Accu-Rite DRO didn't make the move to the new building...it's staying in the old building where my uncle will continue using it to build hot rods and make restoration parts for antique cars...

The Turn-Pro has an Anilam Wizard 450 DRO and was available for setup, so I used it instead of the others...

The Grizzly is a nice mill also...some of your cranks were machined on it, if you sent me a crank last year...
 
Yellowhand

Yellowhand

#14
#14
Each milling machine workstation is set up with an assortment of tooling, including tilt/rotary fixtures and common sizes of end mills in different configurations...I used a 'stub' 4-flute HSS square-corner 3/16" end mill for this keyway...

The last pic is an edge-finder...I'm locating the back jaw of the mill vise and setting the DRO (Digital ReadOut) to find the center of the crank shaft...a DRO will 'find' the center of the PTO portion of the shaft so the keyway is within 0.0001" of perfect location.
 
gbones

gbones

New Member
#15
#15
wow, that looks like some big $$$$$$ in there. i assumed you did all your work at your house, but you know what they say when you assume something:doah:. your 1 talented guy and a valued member here on ye ole OldMiniBikes:thumbsup:
 
Yellowhand

Yellowhand

#16
#16
Some lathe workstations...not quite completed yet.

The CNC operator is Garrett...he's a CAD wizard...and I went to high school with his dad and mom.
 
Yellowhand

Yellowhand

#17
#17
These hydraulic presses work great for bending tubing...the billet dies are made on a milling machine, and a fixture can be mounted to the press...

The material rack has both 7/8" and 1" stainless tubing...
 
Yellowhand

Yellowhand

#18
#18
Let's see who's old school...can you identify the purpose of the light blue machine next to the heat-treat oven in the first pic?...and what brand of wheels got left in the blast cabinet?
 
gbones

gbones

New Member
#19
#19
could you get some videos of all these machines in action:shrug: i know we enjoy the pics, but for folks like me that dont know how they work, it would be great to see how they actually work:thumbsup: maybe a video of you working on a crank would be cool, and i mean a crank from an engine:doah:
 
Yellowhand

Yellowhand

#20
#20
The milling of the shaft was pretty boring stuff...900 rpm, ten passes at 0.010" per pass...the clutch slid right on after deburring...

Let's go home and assemble the engine...
 
You must log in or register to reply here.
Top