Congreve Clock Repair & Rebuild Project

Gallery, Projects and General > Project Logs

<< < (4/5) > >>

raynerd:
Hi guys, I appreciate the input.

The ball is definitely rolling on the bottom as you can see a tiny wear on the track where the ball has been touching. vtsteam, you are also correct in that most congreves I have seen do not have a bottom solid sheet - the tracks are cut right through the sheet. I`m not clear on what you mean about skidding and sliding ? - could you explain a little more.

The only think I have noticed on other congreves is that the grooves come to an end shorter so the ball comes to the end of the groove, lifts out and slides around the rail to fall back in the new groove. It doesn`t jump - it rolls out of the groove and follows the turn on the edge. Others, like in the video below have a continuous track. None seem to have to jump up over the edge like on mine.

Do you agree then if I shorten the ends of the triangles it will improve the situation.

Chris

chipenter:
If the ball is rolling on the bottom try a larger ball first .

vtsteam:

--- Quote from: chipenter on June 23, 2014, 04:16:39 PM ---If the ball is rolling on the bottom try a larger ball first .

--- End quote ---

I like that! :thumbup:

Could be the original ball was replaced at some time.... It might work better with a larger ball.

.................................................................................

Chris, re. sliding contact -- If the ball is rolling on the bottom (or even sides of the lower track) the axis of rotation is horizontal -- parallel to the plane of the bed -- and perpendicular to the direction it is rolling --- just like a wheel if it had an axle. The axle is on the axis of rotation.

But when it encounters the U shaped raised sheet, the axis of rotation wants to change to vertical -- to accommodate the new edge it is riding against. Yet it is also still riding along the lower track -- so the two axes of rotation are fighting each other -- and either one turns to slip and the other remains rolling, or they both partially slip. But a ball can't roll purely in two axis at once. It can have only one axis of rotation.

Since this clock seems so sensitive to a free rolling ball, I'm guessing the friction due to slip is probably significant, where it might not be for another kind of mechanism or equipment .

Further, the slip/friction is not consistent, but happens at the turns mostly. And if the turns aren't consistent either (due to roughness of sheet metal, and the strips loosening) I imagine the timekeeping is inconsistent, and in this case it even stops.

Maybe it wasn't meant to "jump" the strips but ride on them until it hits the U turn sheet, where it rides only on that, lifting above the strips. But it would really need a fine adjustment, and the right sized ball for that.

If it rode only on the U sheet, above the track, the single axis of rotation would be satisfied.

RussellT:
Hi Chris

I've just been looking at the latest video you posted. There's a bit at 1m 23s that shows the turning action clearly and it shows that the triangles stop quite well clear of thesemicircular turning "wall of death".

If the ball rides on the edges of the grooves then as it comes out of the turn it has to get back up on the edges of the grooves, while if it rides on the bottom of the groove then it only has to make the turn rather than change height as well.

A larger ball would certainly raise it up on to the edges of the grooves but if I am visualising it correctly it would collide with the corners of the wall of death.

I think the answer is probably to progressively shorten the triangles (or a dummy one made of ally) and observe the effect on the action. If it has to get back up on the edges then the triangles might need to be tapered in the horizontal plane too.

Given your workshop limitations it might be possible to cut aluminium that thickness with the kitchen scissors.

Russell

tom osselton:
Interesting clock! My take on it is the triangle piece would be the key and should be away from the wall of death by at least the radius of the ball bearing if it extends more than that it will hammer and bounce trying to go in two directions at once rather than using momentum.

Navigation

 Message Index

Go to full version