Oscillating I.C. Engine

[Brian Rupnow]

A crankshaft web in the process of being born. I have decided to make this a 3 piece crankshaft, pressed together. The web is 5/16 crs flatbar. A couple of tricks are involved here. #1--when drilling/reaming the holes for the crankshaft and the rod journal, don't use the mill vice. Put a flat piece of sacrificial plate on top of the mill table and clamp the bar which will become the web to the flat plate. Vices (at least the vices I can afford) always tip the piece being milled a small bit when closed on the part, and if you drill/ream these holes while the piece is held in the vice, the rod journal will orbit as it rotates, and you definitely don't want that. I use an undersize reamer for the two critical holes, at 0.3735" diameter. I use drill rod for the crankshaft, because it comes in at .00025 to .0005" oversize A total of .0002" interference seems about right for this size of stock when press fitted together. If, in my judgement the pieces don't press hard enough, I will cross drill and dowel with a .093" hardened pin.

 

[Brian Rupnow]

Tonight I finished the crankshaft web. The holes are reamed with a 0.3735" reamer. The crankshaft itself is made from 01 drillrod, which is about .0005" oversize, or 0.3755" diameter. The part with blue dye on it is a full 0.3755" diameter, and it will be the "pressed" area. The short polished area at one end has been polished down to 0.3735" for a "lead" into the hole in the web. The long polished area has been taken down to 0.375" to fit through all the bores and bushings it has to go in. I used #220 grit emery cloth strips 1" wide to do the polishing with. When I press it into the web, it will stick out about 1/2" on the "off" side. I do this to ensure that it doesn't go in crooked, which can happen when you are pushing through a relatively thin web---5/16" in this case. I will trim that end off flush with the web after the pressing is done. All pressing will be done with both pieces at room temperature. My 1 ton arbor press is not powerful enough to do this pressing, and my mechanics bench vice won't open far enough to do the job. I will take it to the factory where I am currently doing a bit of design consulting and use their 12 ton press for this operation. When I press in the short piece of crankshaft that the con rod fits onto, I will use my bench vice.

 

[Brian Rupnow]

And check out that crazy bronze exhaust valve push-rod!!

 

[Cogsy]

Looking good Brian. I'm eager to see how your funky looking governor operates/adjusts. At the rate you work at it won't be long.

 

[Brian Rupnow]

The Rupnow Retirement Fund took a big hit today!!! A brand new milling machine from BusyBee. This thing is a monster compared to my old Craftex CT129 that I bought 6 years ago. This one is 110 volt, with a 1 1/2 HP motor. The travel in X axis is 16" and in Y axis is something like 8 1/2". It has an R8 spindle taper. I decided to buy a base for this one instead of making my own from angle iron like I did with my first mill. This thing is majorly heavy compared to my old mill. I know because I just unloaded it out of my pickup by myself with my old faithful cherry-picker engine hoist. It seems to be quite unstable, with high center of gravity. I will arrange some temporary bracing from 2 x 4`s to keep it from accidentally tipping over until I get it to it`s final resting place and can tie the top of the stand into the studding in a wall.

 

[Brian Rupnow]

I can see a problem already. My old mill moved .002" for every graduation on the X and Y dials, and the table moved exactly 0.100" for each full turn of the dial.---On the new mill, each graduation represents .0025", and one full turn of the dial makes the table travel 0.125". It's not a question of which one is right and which one is wrong---It's a matter of me unlearning almost 6 years of moving .002" per graduation.--Wonder what I will screw up first???

 

[Charles Lamont]

You could make a dial with 75 divisions.

 

[techonehundred]

Time to get a DRO and quit looking at the dials.:hDe:

 

[bazmak]

I have the same problem Brian,but each grad. is almost exactly 1 thou,
when you get used to it you can work in both.The mill does look big,is it going in your garage or next to your lathe ?

 

[Brian Rupnow]

Baz--My garage is not heated (much) in the winter. It is below the main bedrooms of the house, so it gets a bit of heat by convection, but not much---water in containers will freeze!!!. I'm thinking I will put the bandsaw in the garage and sell my old mill to make room for the new mill in my little machine shop. I can probably stand the cold for long enough to cut something out on the bandsaw, but I want the mill in where it is always warm.---Brian

 

[Brian Rupnow]

I have an idea percolating--I can probably sell my old mill with all the tooling for enough money to buy a set of decent DRO's for my new mill.

 

[Cogsy]

I had a similar problem when I changed lathes but it didn't take long to adjust. Really though, a DRO would be a nice addition. Congrats on the purchase.

 

[jimjam66]

That looks a beaut, Brian! Old-timers disease being what it is, a DRO is probably the only way to avoid disaster caused by old habits dying hard. Well, based on my experience anyway ...

 

[RonGinger]

Are you sure about those dial measurements? It sounds like you have a metric lead screw, or a 16tpi. I would check that carefully.

 

[Brian Rupnow]

Ron--I did check it carefully. It is stamped right on each dial .0025". I put a dial indicator on the table and checked travel against the dial indicator reading, and with one full turn of the handle the table advances exactly 0.125".

 

[Brian Rupnow]

I just checked with Shooting Star Technology. Their DRO system is actually made in Canada, in British Columbia. For two scales to do the X and Y axis and all the attendant hardware and software, it comes to $812.00 which includes taxes and shipping. That's a pretty hard lump to swallow, but their system is highly recommended by others who have bought the system through Little machine Shop in USA. If I can sell my old mill, along with all the tooling for $1000 I will buy them.

 

[canadianhorsepower]

I just checked with Shooting Star Technology. Their DRO system is actually made in Canada, in British Columbia. For two scales to do the X and Y axis and all the attendant hardware and software, it comes to $812.00 which includes taxes and shipping. That's a pretty hard lump to swallow, but their system is highly recommended by others who have bought the system through Little machine Shop in USA. If I can sell my old mill, along with all the tooling for $1000 I will buy them.

Brian
getting a 2 axes for a mill????? you'll regret for the rest of
your life get a 3 axes

 

[Brian Rupnow]

And behold!!! Tonight we have a finished crankshaft. We almost had a finished con rod, but I got fooled----badly. I hunted around in my "bits and pieces" drawer and found what appeared to be a nice piece of 3/8" brass or bronze. I did my laying out, milled the profile, drilled and reamed the hole for the crankpin, put in the counterbore that the end of the con rod fits into, and was very pleased with myself. It was only on the final cut to part it off from the parent stock that it split cleanly in two!! What the Heck!!! It was only on close examination that I discovered that at some time in the past I had epoxied two pieces of 3/16" brass or bronze together for some reason.---RATS!!! Tomorrow I will make the same piece over again from real 3/8" material.

 

[Brian Rupnow]

Luc, you may well be right. I will check and see what a 3 axis set up will cost. I've spent my toolroom budget for this year, so I'm going to be limited to what $ I can get for my old mill and all the tooling that goes with it.

 

[canadianhorsepower]

Luc, you may well be right. I will check and see what a 3 axis set up will cost. I've spent my toolroom budget for this year, so I'm going to be limited to what $ I can get for my old mill and all the tooling that goes with it.

I got my set up Diltron DRO from japan to US spec 3axes 500.00 taxe and shipping include I still have the name of the agent I deal with.
BTW you got a nice millThm:Thm:

cheers