Looking for tips -- > Cam and Gear assembly

[hemmjo]

I have some questions about Cam and Gear Assembly. I am sure some on this list have experience with this.

I have my old Ford 860 tractor apart to replace the cam gear. The original cam/gear design for this engine,
was a slip fit gear secured with a bolt. The new design is an interference fit between the cam and gear.

Perhaps an interesting side note. I acquired this tractor over 30 years ago, not running, with the cam broken
at the gear. I think that I was sold the new style cam with the old style gear. The gear just slipped onto the cam
and was held in place with a woodruff key and snap ring. Over the years, the gear banging back and forth
against the key eventually sheared off the key. Thus the new gear.

I have pressed bearings in and out or things before, but never measured them. I have no concept
of how much interference is a lot. Text from the vendor where I ordered the gear states,
•This is a cast iron Gear.
•Cam Gear MUST Be Immersed In Hot Oil & Then Pressed On
But it does not say how hot the oil should be.

The gear bore is 1.0000”. The cam nose is 1.0022.
According to an expansion calculator, it needs to be about 500˚f hotter
than the cam to get the bore to 1.003
400˚ difference will get the gear to 1.0024.

Maybe soaking the cam in an ice bath at 32˚ might help. Or dry ice -100˚.
But cast iron does get brittle when cold.

Right now I have the gear mounted in my lathe. The cam is cradled on cardboard
on the cross slide, shimmed to proper height, and aligned front to back.
The other end of the cam mounts on center in the tail stock.



During a cold test run, I can move the gear from the heat, mount in the chuck and advance the
tailstock to press the cam against the gear in 10-15 seconds.

My concerns are, if the gear starts to shrink before it gets pressed all the way on, will the tailstock
be able to push hard enough to finish the job.

I do not have a press to either finish the assembly or remove the gear if the first attempt fails.

Motor oil flash point is around 400˚. I have found that refined avocado oil flashes around 520˚.
But both of these would be dangerously close to burning into flame. So cooling the cam seems appropriate,
but how cold is cold enough or too cold?

I have worked on lots of engines and equipment over the years, but have never done a shrink fit assembly.

Am I thinking too much, making this too hard?

I appreciate hearing some of your experience.

Thanks,

John

[paul_j]

I cannot answer specifically about your Ford cam gear, but I have installed the live PTO gear on several two-cylinder John Deere tractors. I used peanut oil, heated with a common propane fish fryer burner, to warm the gear. The crankshaft [big metal] was installed in the tractor, so no cooling of the crankshaft was possible. I made a temporary wire cage to grasp and handle the PTO gear. I heated the oil to 400 degrees with the gear immersed. I nervously grasped the wire cage with long handled pliers and slid the gear onto the crankshaft. The gear fit so loosely that I had to hold it in position until it cooled somewhat. After cooling, it gripped the crankshaft as needed. My biggest worry was the close proximity of the expensive crankshaft oil seal that the gear was positioned against. I cooled the oil seal with damp shop rags. Several experts told me that 400 degrees would not damage the oil seal, and I am pleased to announce that the seals were undamaged each time that I used this procedure. Best wishes with your cam gear installation!

[tonyfoale]

Your basic problem is not getting the right temperatures it is about getting the right force. You have stated that you do not have a press, in which case you have two options.
1. Get a press.
2. Find someone with a press.

A 2.2 thou interference is easily handled with a press especially if you heat the gear and lubricate the mating parts. You are not going to get enough force in reserve with a lathe tailstock.

[hemmjo]

Tony,

Thank you for the response. I have acquired a 25 ton press frame. Minus the hydraulics. I remembered reading your initial post about inverting a jack.
Inverting an hydraulic jack for a workshop press.

I have a 20 ton bottle jack. I have it apart preparing to install the pump inlet extension. I had intended to make a fitting to press into the inlet hole. The inlet in my jack seems small( 0.160"/ 4mm) Seems if I make a fitting to insert into that, the oil passage will be very small.

I was thinking of enlarging that hole, But I am concerned about getting chips in places I cannot get clean. in order to get one of the check balls out, have to remove the copper washer that seals the pump, but will have to make a new one. I also do not see how to remove the check ball in the bottom of the cylinder.

From the image in your post, your pump inlet looks larger than mine. Perhaps the size is my imagination.



Your thoughts are appreciated,

John

[tonyfoale]

Tony,

Thank you for the response. I have acquired a 25 ton press frame. Minus the hydraulics. I remembered reading your initial post about inverting a jack.
Inverting an hydraulic jack for a workshop press.

I have a 20 ton bottle jack. I have it apart preparing to install the pump inlet extension. I had intended to make a fitting to press into the inlet hole. The inlet in my jack seems small( 0.160"/ 4mm) Seems if I make a fitting to insert into that, the oil passage will be very small.

I was thinking of enlarging that hole, But I am concerned about getting chips in places I cannot get clean. in order to get one of the check balls out, have to remove the copper washer that seals the pump, but will have to make a new one. I also do not see how to remove the check ball in the bottom of the cylinder.

From the image in your post, your pump inlet looks larger than mine. Perhaps the size is my imagination.

Your thoughts are appreciated,

John

1/8" BSP I think. Have you seen my second post on this topic More on improvements to bottle jack shop press.

[hemmjo]

1/8" BSP I think. Have you seen my second post on this topic More on improvements to bottle jack shop press.

I did see that improvement thread. Very nice work. If this press was a permanent thing I might do that. I need my jack to be easily converted back to upright use. I was able to use heat and a mandrel to expand a piece of plastic tubing for a press fit into the pump inlet hole. So far, it works being held upside down in a vise.

The press frame is not mine. I was able to borrow it from a friend. Now working on the spring return, the valve knob, and mounting it on the press with as little modification as possible to my friends press.

Will post a new thread when it is completed.

Thanks for your inspiration.