T head engine by Brian

[Richard P Wilson]

Been there, done that. I machined a special compound translation gear for cutting imperial threads on a metric lathe, 16DP, cast iron, several hundred teeth. Put it away 'somewhere safe' till I needed it. 6 months later i needed it, but could I find it? Searched the cupboard where I thought I'd put it several times, but no. Ended up making another one. 2 weeks later I looked in that cupboard again for something else, and the first thing I saw, leaning up against the side of the cupboard was the original translation gear.

[brian Rupnow]

This morning the engine is assembled to check for clearances. Happily, nothing crashes, and the crankshaft can make a full rotation with the connecting rod attached without any clearance issues. This almost completes the major components of the engine, and now it will be a simple matter of installing the cams to complete the valve train. Thanks for having a look.---Brian

https://www.youtube.com/watch?v=sKWOqnj_kLw

[nickel-city-fab]

You too? I saw my life flash before my eyes when you said that...

Been there, done that. I machined a special compound translation gear for cutting imperial threads on a metric lathe, 16DP, cast iron, several hundred teeth. Put it away 'somewhere safe' till I needed it. 6 months later i needed it, but could I find it? Searched the cupboard where I thought I'd put it several times, but no. Ended up making another one. 2 weeks later I looked in that cupboard again for something else, and the first thing I saw, leaning up against the side of the cupboard was the original translation gear.

[Sparky_NY]

This morning the engine is assembled to check for clearances. Happily, nothing crashes, and the crankshaft can make a full rotation with the connecting rod attached without any clearance issues. This almost completes the major components of the engine, and now it will be a simple matter of installing the cams to complete the valve train. Thanks for having a look.---Brian
https://www.youtube.com/watch?v=sKWOqnj_kLw

Could be a illusion but it appears the engine is quite stiff the way you turn it. I would expect you could spin in over easily with one finger. Videos can be deceiving.

[Tim Clarke]

Could be a illusion but it appears the engine is quite stiff the way you turn it. I would expect you could spin in over easily with one finger. Videos can be deceiving.

Looks like he must have the piston rings installed

[brian Rupnow]

New engines are always that stiff. If they were loose during trial assembly, they would end up with unsuitably large tolerances once broken in. No, I don't have the rings in it.

[brian Rupnow]

Today was ignition points, condenser, and ignition cam day. It also was finish the gas tank day. Everything went as planned. I am going to paint that gas tank and the flywheels, so I probably won't do very much cosmetic work on the brazed joints on the gas filler neck and out-spout. A bit of gloss paint hides a multitude of sins!!

[brian Rupnow]

I spent the day working on a real job, but tonight I'm having a close look at this engine. I think that other than the flywheels and gear covers, everything is finished. I'm waiting for my cams to arrive, and there is a bit of finessing to connect the cams to the large gears. I don't need the gear covers to start the engine, so this could get exciting pretty soon. I'm still on the fence regarding the flywheels, but I want to go down to my nut and bolt store and look at something. They have a bin full of casters down there, and I remember seeing some large aluminum casters with rubber bonded to the outer rim. I have some double extra strong schedule 80 pipe here, and if I could machine the rubber off those aluminum casters and put some heavy wall pipe around the aluminum, it might make some nice flywheels.

[oxford]

Today I have prepared a piece of 01 material to make two cams from. The length of the piece is determined by the depth available in the three jaw chuck which is attached to my rotary table. The center diameter is determined by the maximum bore inside the chuck. The diameters at the ends are equal to twice the 0.382" dimension on the drawing, which determines the size of blank to cut the cam from. The material is just long enough to grip in the three jaw chuck with 3/4" of material stuck up above the chuck jaws. The cams will be .688" long, which should keep the cutter above the chuck jaws. I go a little bit crazy every time I make a cam, because I don't do it often enough to remember all the set-up steps. Attached are the picture of the prepared stock, a drawing of the cam, and a model of the milling machine cutter and the cam in their relative positions on the milling machine. The milling cutter will be turning clockwise, and the center of the mill spindle will be offset from the centerline of the rotary table chuck by 0.346" and 0.200" which, as you will notice on the drawing is the centerline of the flank radius. This should give the cams being cut a 99% chance of matching the drawing. Every time I do this, I write myself a bunch of notes on how to do the set-up, and then read thru all of my notes before I do it again.

Brian, do you have any pictures of your setup when cutting the cams? I am having a hard time visualizing what you are doing based off the “notes” drawing.

[sid pileski]

Btw Brian, when the cams show up, you will have to indicate the .375 ID bore, as that bore is not concentric to the stock I used.
Sid

[RB211]

New engines are always that stiff. If they were loose during trial assembly, they would end up with unsuitably large tolerances once broken in. No, I don't have the rings in it.

Interesting, this is the opposite of steam engines which are made a bit loose to allow for expansion as everything heats up. Well, unless the engines destiny is to be run on compressed air.

[Richard P Wilson]

Interesting, this is the opposite of steam engines which are made a bit loose to allow for expansion as everything heats up. Well, unless the engines destiny is to be run on compressed air.

Steam or IC, I make 'em tight, then motor them over for half an hour or so before starting up (or trying to)

[J Tiers]

New engines are always that stiff. If they were loose during trial assembly, they would end up with unsuitably large tolerances once broken in. No, I don't have the rings in it.

Steam or IC, I make 'em tight, then motor them over for half an hour or so before starting up (or trying to)

I find this puzzling to some degree. Maybe I just do not "get it".

It seems to be based on the idea that the machining is not perfect, so there are a lot of bumps and ridges on the cylinder and bearing surfaces, which need to be worn down. If the surfaces were smooth, it would appear that the engine could be made to dimension and would run fine right away.

The big source of friction, the piston, is often lapped to the cylinder, so it should be very smooth. Alternately, it is made slightly loose because the rings do the sealing. So that ought not to be an issue.

Automotive engines were, as far as I know, never made too tight to run, although older manufacturing techniques did require a period of "break-in" which is again just wearing down the bumps and ridges. But they were made with enough clearance to run as-built (although not actually "loose").

I do not make model engines. But the things I make with journal bearing fits etc, I do not need to make so tight that they need run-in just to function. Why is that required for engines?

[sid pileski]

It’s not required.
I think it’s a mater of experience, patience and to some degree, the type of equipment a person may have.
Im not going to Knock anyone’s work. But we all have different levels of gifts. And, in the end, most times they run. Brian has displayed this many times.
If I were to have an engine that turned that tight, without rings, I probably would go back and fix,remake.
But in the end, “running in” gets you there.


Sid

[J Tiers]

Not knocking Brian at all. It certainly works for him.

Just wondering about the comments, the ones made here, and ones I have seen elsewhere. Some folks insist on the "make it tight", others insist on NOT doing that.

Figured I'd ask.