Author Topic: Offenhauser Inline 4 cylinder, Might Midget Model Engine Build, 1:4 Scale  (Read 6151 times)

Offline jirvin_4505

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Re: Offenhauser Inline 4 cylinder, Might Midget Model Engine Build, 1:4 Scale
« Reply #30 on: October 04, 2022, 09:18:43 AM »
Amazingly detailed work. Thanks for the description of the processes

Cheers Jeff

Offline eccentric

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Re: Offenhauser Inline 4 cylinder, Might Midget Model Engine Build, 1:4 Scale
« Reply #31 on: October 12, 2022, 04:00:53 PM »
Roger,

I used a "serpent's tounge" shaped tool on the  journals. I ground a cutter from a piece of HSS as shown below. The intent was a broad faced tool at exactly 90 degrees to its length, with a radius on each side and a notch in the middle to reduce the amount of the tool in contact with the work piece. I have generous reliefs on the face and sides.  I get a fair amount of chatter because of the amount of tool stickout, so I run the lathe slow (250 RPM) on the final passes. I go in with the tool and then work it back and forth until no more material is being removed.  With a tool of this shape it is hard to get it perfectly lined up with the work piece.  I will use dykem on the journal then move the tool back and forth removing a small amount of material, then measure the journal diameter across its length with a micrometer.  If the tool is not exactly straight on, one side will be a bit smaller than theother, and I will adjust the tool until I get equal measurements on the full length of the journal.  I hope that makes sense.

Lee,

I made the crank as a single piece becasue that is the way I made the crank on my first IC engine, Westbury's Kiwi MK2.  Not a great reason.  I have only silver soldered once, with mixed results.  I will silver solder the exhaust and intake, we will see how that goes.  This four cylinder engine has the pistons offset in pairs and is naturally balanced and does not need counter weights as a pair of conrods opposes the other pair.

Alex,

Yes the oil pump will be gear type without any regulation.  We'll see how that works.


« Last Edit: October 12, 2022, 04:11:19 PM by eccentric »

Offline Roger B

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Re: Offenhauser Inline 4 cylinder, Might Midget Model Engine Build, 1:4 Scale
« Reply #32 on: October 12, 2022, 07:37:33 PM »
Thank you  :) After various experiments I have moved on to using an insert parting tool with a width of 2.2mm. As you say it has to be set square. This was making the 360° crankshaft for my 12cc twin.
Best regards

Roger

Offline eccentric

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Re: Offenhauser Inline 4 cylinder, Might Midget Model Engine Build, 1:4 Scale
« Reply #33 on: October 12, 2022, 10:54:21 PM »
Roger, looks good.  does the parting tool have enough radius at the two sides?  Don't want too sharp of corners there.  [edit] I zoomed into your picture and the radius looks nice.

Offline eccentric

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Re: Offenhauser Inline 4 cylinder, Might Midget Model Engine Build, 1:4 Scale
« Reply #34 on: October 19, 2022, 10:05:03 PM »
Offy – First Gear
The Offy has a lot of gears in the timing gear train and I want to have the gear tower populated before I fabricate the camboxes to insure I have the proper gear mesh between the gears in the gear tower and the camshaft gears.  This sequence is how I make gears.

I make a sacrificial gear arbor in the lathe, putting grooves as shown for the super glue to seep into.



I cut the blank from the mother material, in this case brass, center punch the center.  I super glue the blank to the arbor, using a live center in the tail stock to center and put pressure on the glue joint.



Once the super glue is cured, I drill the shaft hole under size and ream to the shaft diameter, in this case 5mm.


I don’t completely trust super glue in this application so I also use a screw, not to center but to secure.  So I drill and tap for a 10-32 screw.


I turn the blank OD down to size.  In this case we are making a 54 tooth .5 Module gear with an OD of 28mm.

The CNC is used to cut the teeth.  If anyone is interested, I can provide the Gcode file to do this, it is quite simple.


After the teeth are cut, I turn the gear again on the lathe bringing the OD back down to the proper size.  The gear cutter throws up burrs that are removed in this way.  The gear is faced and the .5mm X 7mm spigot is machined.


I heat the gear and pop it off of the arbor. The arbor is refaced and a pocket is machined to match the spigot.


The gear is again super glued into place using the spigot and tail stock to align the gear to the center of the lathe.


Again a screw is used to secure the gear to the arbor and the gear is turned down to final thickness.  The screw is removed and the spigot is carefully turned down, I remove .005″ of material at a time so I don’t bust the super glue joint.


I lightly touch the teeth edges with a file to remove burrs created from the facing operation, but not much, I want to maximize the tooth engagement surface area.  Finally I clean up the teeth with a piece of folded 600 grit sandpaper to clear the last of the burrs from the teeth.





Offline crueby

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Re: Offenhauser Inline 4 cylinder, Might Midget Model Engine Build, 1:4 Scale
« Reply #35 on: October 19, 2022, 10:26:42 PM »
Excellent work on some very small gear teeth!
 :popcorn: :popcorn:

Online Admiral_dk

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Re: Offenhauser Inline 4 cylinder, Might Midget Model Engine Build, 1:4 Scale
« Reply #36 on: October 20, 2022, 10:57:42 AM »
Great way to make tiny Gears - thank you for showing  :ThumbsUp:   :cheers:

Per

 

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