So I've been busy making the bushes for the top mounted shafts & bottom mounted bearing assembly. The top bush was relatively straight forward, just needed to fit into the hole in the damper bar & have a 12mm hole reamed in it. I deliberately bored the hole small before welding it into the bar then finished the hole to size once I'd mounted it back on the mill, that way if the heat of welding had made it distort in anyway I could bore the holes for the rods all square & parallel with each other.
Bush sitting in it's position all ready for welding.
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I chamfer the area I'm going to weld so that I can dress off the weld that's sitting proud but still have enough weld holding things together! Although I deliberately designed the bushes (all of them) so that the load is taken by the shoulder on the 'top' of the bush & the weld is merely holding things in place.
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I had a small 'technical oversight' to do with the springs which I will come to shortly but here's a picture to explain 'clocking up'.
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(again apologies to anybody that's familiar with clocking up but just to explain it to people that aren't)
You mount a Dial indicator into the chuck on the mill & touch it on the job. You then move the table around in the X & Y planes until the indicator (clock) reads the same all the way around when you rotate the chuck through 360 degrees. This mill, whilst not CNC does have a digital readout mounted on it so you then Zero the X & Y axis on the readout. You then know that the job is exactly on the same centre as the chuck you can then move the mill anywhere you like but can always return to 0,0 & know that you are exactly back at the point where you started.
So,onto my cock up! I bought some springs from the local bunnies thinking that I didn't want them to big a diameter but not too small that the ID touches on the ground rods (I don't want any extrenuous vibrations!) & thought I was being clever & found the perfect size & wire gauge, just a nice diameter e.t.c e.t.c!
Machined a spigot onto the bush so that it positively located the spring & stopped it touching the rod.
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Then realised that while it was all peachy at this end I'd over looked the fact that the bearings were 22mm outside diameter so the 16mm OD spring would be sitting directly on the rubber sheild of the top bearing!
Here's the bush the bearings sit in (there's two in each assembly to provide some 'stability insurance') prior to welding it in, you can sort of see my dillema ( I repeat
!)
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And here's the bearing, complete with offending rubber sheild
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So after scratching my head & arse for a bit (not one after the other) I thought of making a cap that went into the recess at the top of the bush, the hole in the cap will be a clearance on the rod & it will have a pocket just slightly bigger than the spring OD machined in which will positively locate the spring at this end!
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Right next problem....I'd machined the bushes and the edge at the top was 3mm wide, gonna need some small screws to hold the cap on so I went with 2mm stainless cap screws we have in stock here. Back to the mill to drill & tap the holes in the bushes & caps. These small taps make my bum twitch, usually when I'm tapping stainless steel but Ally can cause a problem too if you let the swarf build up in the tap's flutes so nice new taps & regular cleaning out of the hole & tap's flutes & plenty of Kerosine (the cutting oil usually used on Ally) usually solves it but as you are turning that tap wrench the pucker factor's still up there!
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A bit of a blurry shot (although the mat in the background is in perfect focus!
), I put a centre into the back of the tap wrench so not only is the hole tapped square bit I also don't 'wobble' with the tap & snap it ( with these small taps it's easy to twitch or sneeze or something only to have half a tap in your hand & the other half firmly still embedded in the hole & no means of easy removal
)
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So,anyway I managed to
not break a tap
Job done
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Just a quick photo showing the bits that make up each bearing unit.
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Once the caps were all done I welded the bushes into the lower bar, a small amount of distortion occured due to the heat of welding which required running a reamer down the bearing bore to skim out a few tho from the end I'd welded then I assembled the bearings into the bushes. The damper bar runs nicely and easily up and down so I couldn't help but 'dummy' the frame up again & grab a picture
It looks a little industrial at this stage but should 'refine' itself with some paint on it & the weight isn't a problem, this little lot can easily be lifted in one hand.
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Anyway that's where I'm at currently and I'm away for the weekend so there won't be much getting done on it but I'll put another post up when I have some more to share. I hope there's not too much info for you guys & you are getting bored, as I say, when you do this all the time it's hard to know what others might find interesting. But I will eventually get to "the business end" of the project & actually make some sound producing bits of ally!