LR2-LR3 The Longest Conversion (AUS)

SupraGuy · September 16, 2023, 11:48pm

Should be easy enough. I use a solid copper wire between the tubes and a printed plastic plug on the control box side of the beam on the LR3, with a ground wire that goes to the IEC socket where I get power.

Bonus, by grounding the bottom rail, which is in contact with the bottom rail bearings, which are in turn in contact with the 5/16" bolts, a ring terminal on one of the bottom bolts serves as a ground point good enough for a ground wire down the dust collection hose. (I wouldn’t want to count on that ground wire for a safety ground, but it’s good enough for the purposes of static electricity control. (I soldered a bit of 16AWG wire with a bullet plug onto a 5/16" washer instead of a ring terminal.)

bitingmidge · September 17, 2023, 2:31am

Prototyped the final version of the emergency stop this morning - I was mucking around with thoughts of boxes and printed recesses, and although I’ve described it above the solution couldn’t have been simpler.

The estop fitting has a panel mount thread, so “make a panel”. Just drill a hole in a bit of MDF to suit the panel diameter, and a bigger one to recess it to taste.

Here of course I have a ply facing so the “bigger” hole is actually right through that, or around 15mm than it appears to be in the MDF. (I’m not sure if trying to make things clearer didn’t just do the opposite!)

The end result after a bit of chamfering with the router is a stop which is “almost” flush with the face of the table when stopped, and protrudes far enough to be useful but not so far that it will get caught on things (I hope) when it’s in “go” mode.

bitingmidge · September 17, 2023, 10:01am

Well it’s this evening now, and I chose not to dismantle my brad nailers and simply clamp the perimeter ply pieces on. This did take a bit longer than it might have, but I did think to check for square before gluing the mitred corners on, and I was about 4mm out (before pulling it back into shape) which isn’t bad given the amount of moving and thumping it’s suffered.

Tomorrow it looks as though I’ll get the wiring in easily enough, and with just a teensy bit of luck, it’ll be skinned by the evening.

Some of you may recall that I forgot to add the hole for the E-Stop switch in the first round of gluing. So I chopped out a section and added one with a hole - no I couldn’t do it with a battery drill from behind - it’s that recessed thing that needs a drill press and some forstner bits!

Anyway that left a bit of a potential for misalignment of the holes between inner and outer faces, so I made a big circlip out of PLA to register the two pieces perfectly while I mucked around with assembly, and now when I glue them up I’ll be sure that the stop button will be in the centre of the outer part too.

Jonathjon · September 17, 2023, 1:17pm

@bitingmidge I have to say you’re attention to details most don’t even think about truly amazes me. This is going to be one amazing LR3 when its done! Keep up the amazing work sir!!!

bitingmidge · September 17, 2023, 1:55pm

Thank-you, it’s going to be embarrassing if I can’t get it going!

Jonathjon · September 17, 2023, 1:57pm

I have no doubts you will get it going! But if not you’ll have the best looking workbench ornament on the forum! LOL

vicious1 · September 17, 2023, 3:04pm

I was putting my table together yesterday and started thinking about skinning. I will glue and nail the bottom on, but what about the top? Permanent- Glue and screw, when the glue dries remove the screws, or swappable- deep counter sink a bunch of screws in the surface?

Jonathjon · September 17, 2023, 4:18pm

On both of my LR3 I took and countersunk the screws as far as my countersink bit would go. That keeps the screws down plenty. No glue. That way when I surface enough off that its time to replace it can easily come up and replace with a new sheet.

Tokoloshe · September 17, 2023, 7:37pm

Does not matter, it’s going to look good. Who needs to actually cut stuff anyway?

Tokoloshe · September 17, 2023, 7:38pm

I just put another spoilboard on top.

vicious1 · September 17, 2023, 8:00pm

Well, yup I do think that is the best idea. Glue and countersink the first thick one. If it even gets too thin just surface and drop another on top.

Thanks!

bitingmidge · September 17, 2023, 8:22pm

The trouble with no permanent top skin is that it doesn’t stay rigid while you are “re-skinning” it so you lose the benefit of the torsion effect… I am just gluing and clamping 3mm MDF skins top and bottom, then I’ll use a screwed 16mm spoil board (with a couple of plot twists) into the subframe…

I’m using the LR2 table frame, and still have the possibility of tilting the top it as originally planned if I need to minimise the footprint a little (unlikely now that I’ve reshuffled everything in the shop).

On the LR2 the spoilboard was a “press fit” between the glued “tracks” which were also 16mm MDF. Arguably it was a complete failure as I didn’t want to risk damaging it so I used to clamp another board on top to protect the spoil board!

This one will have similar permanent “tracks” and the spoil board will be in three identical pieces, each roughly 500 x800 (screwed).

That will allow easy replacement, flipping or swapping of any panel without having to replace the whole board when just a part of it gets chopped up, and more importantly I can buy 600 x 900 or 1200 boards that are much more easily handled than a full sheet.

At what point does your table get too high to see over?

Here’s my LR2 table (build diary for the table starts here)

Tokoloshe · September 17, 2023, 8:25pm

My choice of words was shitty. I screwed down the torsion box top, 18mm plywood, because I might have to access the suction table’s pipes sometime.
The spoilboard on top of it is held by sheer force of will (and I framed it with aluminium channels to clamp down stuff). I’d be pretty surprised if the LowRider was able to lift a 90x120cm, 18mm thick sheet of MDF.

Jonathjon · September 17, 2023, 9:01pm

Makes sense. Wasn’t thinking about it being a torsion box. Mine is just a bunch of MDF on top of some cabinets LOL. Had to build storage to get the ok to build a new table LOL. Now I just need to finish the cabinet drawers, shelves, doors… LOL

bitingmidge · September 17, 2023, 10:11pm

That’s actually the simplest way of building a flat and very stable table!

Jonathjon · September 17, 2023, 10:15pm

Thanks. I’m happy with how it turned out. Just need to find time to finish it. Only down side to it is its HUGE lol. I went taller than I should have (I HATE bending over, even have my cabinet table saw sitting on top of 6x6’s) but over all I’m happy with it. I do have one row of drawers built and installed, top most being CNC bit storage lol. That has made life a lot nicer. Have all the drawer slides to make 2 more rows of drawers and plan for 3 open cabinets on the other side. Will be nice when its all done… if its ever done LOL

jeffeb3 · September 18, 2023, 2:49am

The top doesn’t have to be thick. But the glue is important, I think. Think of those hollow core doors. The thin on those is thinner than an amazon shipping box. We want more strength, but 1/2 or 3/4 is probably overkill.

I glued down 3/32" hardboard and held it in place with nail gun staples. Then I attached a 3/4" sheet through that to the torsion core with countersunk screws. IIRC, I only put screws on the outside edge. It was really rigid and flat. I still have it, but it isn’t part of my LR anymore.

bitingmidge · September 18, 2023, 3:06am

Think cardboard carton. Really rigid lightweight structures just need to be constrained at the corners, but in the case of a table all those bits inside just help to keep the skins apart.

And you’d think after all the effort that I’ve been putting in, I’d have the patience of Job (that’s the bloke from the old testament not the bloke from Apple), but it doesn’t work like that.

After a late night watching F1, I woke up too grumpy to fix the stapler/brad nailer so thought I’d get on with it anyway.

I remembered to check for square (less than 1mm), and level (as close to zero twist as I can measure) and clamped a couple of chocks in place so that nothing could move., and after that things went slightly downhill!

I cracked open a new bottle of PVA glue, without for a minute thinking it would be much less thixotropic than the year old one. All went swimmingly until I realised that there were runs all over the place which meant I was actually gluing the thing to my bench, and of course there was no way of knowing what was going on.

So I flipped it over (cleaning the bench while balancing the thing on edge) and made a perimeter of clamps and packers while hoping the glue wasn’t going off too quickly. Wasn’t happy with how level it wasn’t so cleaned up the runs and flipped it again, only to discover that my clamps made it all too tall to flip.

In the end I did manage, and discovered that one of the advantages of having several unfinished projects is all that glued up furniture blanks lying around make nice presses.

I think it’s be OK, but I have three or four dozen clamps that need to go back in their rack and I’ll fix the stapler before I do the other side this evening.

bitingmidge · September 18, 2023, 3:57am

There are a couple of things to remember here - both the top and bottom skins are working together - or technically against each other. All we need is sufficient “strength” to deal with the span (live and dead loads) and the cantilever loads, which are dealt with by the bottom and top skins respectively working in tension. All we need is enough thickness to deal with that tension so 3mm of custard skin is more than enough.

Of course then we need a top, or spoil surface to deal with the point load. I’m not terribly keen on the (torsion box with cantilevered ends) style of table - as the structure has to be sized to suit the cantilever, and it is not taking advantage of the stressed skin at all. (I told you I woke up grumpy!!)

bitingmidge · September 18, 2023, 4:49am

It looks as though I’ve dodged a bullet. It’s still square and flat, not that square matters and I’m going to round off the corners anyway.

There was one spot in which gluing was a little problematic, but it’s a long way from the working surface and it’s clamped now so by tomorrow it’ll be fine.

I think I will glue the top on with no fixings as well (just to see if it was a fluke) but I’ll wait till tomorrow till the glue cures completely. No sense pushing my luck too far, and I’ve got some detail work to do yet anyway.