Post by dickdastardly40 on May 6, 2008 13:14:09 GMT
Possibly a whole thread's worth in both eccentric turning and trepanning with a multitude of differing techniques.
A method for an eccentric outcome without a dti is to drill a hole offset to your centre axis in the drill press, tap and fit a threaded rod to suit.
Using the 4 jaw you can 'suspend' a dead centre into the centre mark (providing it's bang on)with another dead centre up its chuff which is in the tailstock. This method is sometimes known as the 'wobbly centre' As you rotate the 4 jaw you would normally have a DTI bearing on the suspended centre and you adjust to bring the runout to zero. With no DTI you could use a scribing block or a point held in the tool post. Gently rotate the chuck until the dead centre is closest the point. Move the point until is just touches the centre, rotate the chuck half a turn and adjust the jaws so that the job moves the dead centre approx half the distance closer to the point. Half a turn back and check, then 1/4 turn adjust to the closest etc etc. When it seems good nip up all jaws and recheck, spin by hand and watch for runout. Clear as mud?
Trepanning is really only boring but without removing the centre section, grinding a specialised tool is required for narrow grooves but you can do it with a boring bar and a couple of different tool positions for a wide slot such as yours. I'd drill afterwards so that I wasn't cutting intermittently.
I Still think it looks good despite you saying where the inconsequential flaws are.
Cheers Al; I've read that several times now and I think the mud has cleared a little
Once I've finished this engine I'm going to make a boring bar with sufficient length yet narrow enough to be useful on these little engines. I've got a Glanz one and a HSS one but neither are ideal.
I made the valve yoke today - lots of careful filing to get the oval hole and the curves right. Before bending over the ends I tested my technique on a scrap from the same piece of sheet - good thing I did as it snapped clean off as soon as I touched it with the soft-faced hammer! I annealed the broken bit and re-tried it and it worked fine so I did the same with the actual part
The finished article is the right size etc but IMHO it's not a great design, like some of the other parts!
Here's the valve yoke sitting on the eccentric bit of the flywheel, both of which still need some titivating. I just need to make the cylinder end covers and this engine is done and dusted.
Ah, glad you asked! In view of the fact that the previous Scotch yoke engine wouldn't run on the aquarium pump I'd like to see if I could make a rotary valve engine that will. I've got a couple of sets of plans but I need to see how much work would be involved in metricating (!) them.
I've also been reading up on a starter Stirling and revisiting another hot-air engine from an old book.
Either way I feel like I've advanced a bit with this engine; a little more honing and steam will be back on the menu ;D
EDIT: Updated the video to include a commentary - sorry about the soporific ex-Black Country style LOL.