Clamshells

[tentacles]

So I machined my first (prototype) clamshell today, used some asstastic pitted aluminum barstock to do it, but the important parts look nice..

 

 

 

 

 

 

You can remove the rocket tube from the sleeve by merely loosening the bolts and shoving it out - or taking the halves apart completely.

 

What does it take to make one of these?

 

A lathe, you'll need a bed long enough to work 14-18" between centers.

4 jaw chuck

1/2" drill bit

S&D(Silver and Deming) drill bits, 5/8-1"

3/4" Boring bar

3/16 & 1/4" drill bits

1/4-20 Tap (and tap handle)

Several lathe tool bits (to face the ends)

1"x2" aluminum stock, 2 pieces, 6" long

1/4-20 x 1.5" bolts, 4, with washers (can be thumbscrews or similar)

Your lathe tailstock drill chuck needs to be 1/2" or bigger and of good accuracy for the drilling operations

 

Optional but good:

Milling machine (to face the sides of the aluminum that go together and to accurately drill and tap the holes)

A digital readout for your crossslide (makes boring operations less painful)

Beer (something hoppy)

 

The machining procedure is something like this:

 

Put the 1x2" slabs in the milling vise and fly cut/facemill one (or more) faces of each flat.

 

Place the two flat faces together in the vise, and drill the holes for the bolts, drill them all the way through both pieces 3/16"

 

Remove one of the slabs and drill the holes in the remaining piece to 1/4" (or slightly larger) for the bolts to pass through.

 

Tap the 3/16" holes in the other piece.

 

Deburr the various holes and edges

 

Optional: use a deburring tool to cut slight chamfers where the pieces mate together.

 

Bolt the pieces together

 

Chuck in the lathe, center the piece. I used the above chamfers to locate two of the chuck jaws along the centerline (important!) and then took light cuts at the face and adjusted until that end was centered to my liking. This probably isn't nearly such a PITA with stock that isn't pitted as all hell.

 

Face the end of the stock, and then remove it from the lathe chuck and chuck it in the other way

 

Again, center and face the work

 

Drill down the center of the stock, I started with a *sharp* 1/2" split point drill bit

 

Work your way up through the S&D drill bits until the piece is bored out to 7/8". Make a shallow test cut with the 1" bit to ensure it isn't cutting the hole too big for your tubes. If it's not (undersized or adequately sized) then drill out the whole thing with it. I had to make a drill bit extension, it's just a piece of 3/4" stainless that I bored at one end for .500", drilled and tapped for a set screw and turned the other end to fit my lathe drill chuck. I machined a flat on the shank of the drill bits so the set screw holds them in place without turning.

 

If needed, use the boring bar to open the hole up so that your tubes are a snug fit.

 

Total time: Like 6 hours, but I wasted at least an hour fiddling with the chuck alignment (because of the shitty stock) and another hour or so making my drill bit extender. And probably yet another hour just plain wasting time. I think I can make my next one in about 3 hours, maybe less.

Edited February 21, 2009 by tentacles

[Swede]

You dog! I'd be chicken to do a 1" with a lathe. The finish you got on the bore is outstanding... those are going to make some kick-ass motors, no doubt.

 

Well done!

[Richtee]

So I machined my first (prototype) clamshell today, used some asstastic pitted aluminum barstock to do it, but the important parts look nice..

 

 

 

 

 

 

You can remove the rocket tube from the sleeve by merely loosening the bolts and shoving it out - or taking the halves apart completely.

 

Sigh...yer sooo good! Knew I should have took metal shop.

[ActionTekJackson]

Dang, I have one of these made out of wood. Nothing like this though wow.

[Aquarius]

@ActionTekJ: Mind posting a pic if you have one?

I use mainly wood myself, it's easy to machine, cheap and readily avliliable.

And the drillbits'n pieces dont't cost a fortune. Never made a clamshell-type sleeve though.

Hmmm...Maybe my next project?

[tentacles]

Wood is an interesting proposition.. With the right species I'm sure it's do-able. The main concern would be warping, so you want a very stable wood. If you can get Ipe in your area (check fancy lumberyards for "ironwoods" decking) it's extraordinarily stable, and unbelievably hard.

 

I've been busy this weekend, see below -

 

 

Yep, I made three more clamshells on Sunday. I tried a different method of drilling them, specifically I used my boring bar holder to drill using the cross-slide on the lathe, so I didn't have to turn that damnable handwheel on the tailstock so much. I just flipped on the power feed and let er rip. The holes aren't as clean, they come out 1.005-1.007" which means they're a tight fit for the tubes, no boring bar needed. They're not as shiny and pretty of course, but that's not necessarily such a bad thing. I understand if they're too polished, the glue from the tubes will adhere to the support making them very difficult to remove.

[Swede]

Tentacles, do you have a big drill press? Or can you mooch time on one? When I moved into my current home, the guy had a giant 3-phase drill press that he didn't want to move, and I basically got it for free. If your 1" S & D drill is doing a good job, I'll bet you could do the drilling on a heavy drill press, if the horsepower is there.

 

Lathes are great for precision boring if the job requires it, but these clamshells don't need to be too precise. Have you had any problems with the finished motors getting stuck at all?

[ActionTekJackson]

@ActionTekJ: Mind posting a pic if you have one?

I use mainly wood myself, it's easy to machine, cheap and readily avliliable.

And the drillbits'n pieces dont't cost a fortune. Never made a clamshell-type sleeve though.

Hmmm...Maybe my next project?

 

I don't have any pics at the moment, its at the shop. It'll be a bit before I can go back and take some. Basically all I did was take two 2x4's cut them 1/2" longer than my rocket tubing and then used a drill with a grinding bit and ground out a channel on each peice so that respectively half the tubes outer diameter would fit in each peice. Thus completely enclosing the rocket tube when the peices are placed together. I then drilled four holes, one in each corner, completely through both halves and used some bolts with wing nuts to clamp it all together. Fits right on my tooling set. If I can remember I'll try and take some pics when I get back to making some stuff (fourth of July is coming up after all :-D)