Mount Trapezium

[redhouseluv]

Another small scale bit today, this time the valve rod gland which needed a lot of filing and worn fingers!

[crueby]

Came out great! Looks like you have the valve itself all sorted.   

[Michael S.]

Hello Sanjay,

The stuffing box looks good 👍.
I always file it too. But it's much easier if you first make the round flange on the lathe and drill the two holes for the screws.
Then I mark out the oval shape and then file it. Then you have to file much less material, and it's faster, too.

Michael

[redhouseluv]

Thanks Michael, that's good advice, I'll have to remember that for next time 

[Admiral_dk]

Does having a larger flywheel mean more torque for both model and real-world engines? It kind of feels like it should but I'm not sure mass naturally equates to torque ...........?

NO - but it increases the Rotational Inertia - that again ensures that the the Crank (and Engine) will have an easier time keep rotating between Power applied to the Crank + smoother speed ....

Per           

[redhouseluv]

Thanks Per,

Also on larger, slower rotating engines the governors hardly look like they are doing anything (are they?), whereas on the smaller engines they are flying? I appreciate the speed/energy will make the balls spin out more and vice versa

Lot's of questions today, always learning new things on the forum! 

[redhouseluv]

Eccentric boss diameter question

Mr Keats is back out for the second time this year and I'm machining the eccentric. Does the thickness (outer diamter) of the boss matter? It's about 0.015" thicker than 0.675" as specified, but it looks right i.e the edge of the boss meets the outer diameter of the eccentric (see pic)

[Jasonb]

I doubt it matters, go with what looks pleasing to your eye.

[redhouseluv]

  thought so, but best to check 

[redhouseluv]

Finished the eccentric and it's not looking too bad; moving onto the strap next then the bent eccentric rod

[crueby]

Nice!  How is it held in place, set screw in the boss?   

[redhouseluv]

Nice!  How is it held in place, set screw in the boss?   

Good point ...........not quite finished, 2 x 6BA set screws in the boss

[redhouseluv]

I'm probably being over-cautions by the instructions/diagram relating to the eccentric strap. The diagram shows 0.563" from centre to bottom edge and 0.668" from centre to end of spigot. The wording says cut the strap in half and solder together, but will that work?

I presume the 0.563" from centre to edge is the outside diameter and can be made once the strap is on the rotary table and the centre to the spigot can be made reducing the spigot length?

[crueby]

Personal preference, but I like to drill the screw holes in the side tabs on the strap  to hold it together, to not depend on the solder alone. I'd  do that after cutting and trueing the cut faces. The screws give extra strength for the other shaping steps.

[Jasonb]

My usual method is to machine approx equal off both sides to bring to thickness.  Ditto the two bolt lugs. Saw in half and then mill the sawn edges clean and at the same setting do the tapped holes in one half and the clearance holes in the other. Turn them up the other way and mill the lugs to 1/8" thickness. You can then hold it together waith a couple of cap head screws so it can be bored and the outer radii machined.

The drilling & tapping can be done before sawing in half if you prefer.