[jhudler]

What I had in mind was first creating a special nut to use as a lap. Perhaps casting one around the screw using babbit or lead or plaster or plain old epoxy would work. The lap would be six or eight inches long.

I would read about Henry Rowland and his adventures in making lead screws for ruling engines.

[Dan S]

Acrylic Water would be in the category of paints, it's an emulsion that dries.
It does not cure with a hardener like epoxy (almost no shrinkage), or catalyze like Polyester (a little to a lot).

I stopped by hobby lobby on the way home from work today and they had this stuff it's a 2 part epoxy. haven't found an MSDS or anything like that yet though.

http://www.crafta.com/32012-z.html

[jhudler]

Dan, What does it say on the front. I can't make out the ingredient.

[Eson]

Well... I guess that would depend on how much hydraulic force you can exert and the point at which moglice detonates from dieseling.

Are you creating fixed opposable air bearings?

Jack

Well im not sure what i am creating since i cant decide! Im sort of just exploring the possibilities. However my dream is a tri/hexapod with linear actuators and the hydrostatic/air bearing would support the ballscrew since ball bushes will build too much. I have CAD-drawings of my idea but not avalible now.

[jhudler]

It's a Urethane (Isocyanate), not an epoxy.

http://www.pdmurethanellc.com/quick-water.htm

[jhudler]

I stopped by hobby lobby on the way home from work today and they had this stuff it's a 2 part epoxy. haven't found an MSDS or anything like that yet though.

That Quick Water is almost 3 time the cost of epoxy.

go to http://www.uscomposites.com/epoxy.html and order the EPOX-6355561 (16 oz part A and 8 oz part B).

If you order it by tonight you should have it by Thursday.

Jack

[jhudler]

Well im not sure what i am creating since i cant decide! Im sort of just exploring the possibilities. However my dream is a tri/hexapod with linear actuators and the hydrostatic/air bearing would support the ballscrew since ball bushes will build too much. I have CAD-drawings of my idea but not avalible now.

Are you trying to build something like a Hexagide?
http://www.indoor.flyer.co.uk/kinematic.pdf (third picture or so)

[Dan S]

That Quick Water is almost 3 time the cost of epoxy.

go to http://www.uscomposites.com/epoxy.html and order the EPOX-6355561 (16 oz part A and 8 oz part B).

If you order it by tonight you should have it by Thursday.

Jack

I have half a gallon of general purpose system 3 epoxy. I worked with several different brands in the past, I'm just worried about mixing up such a large batch (worried about the heat). Though to be honest, i have never mixed up a batch with a bunch of aggregate in it, so maybe that will suck up some of the heat.

[jhudler]

I have half a gallon of general purpose system 3 epoxy. I worked with several different brands in the past, I'm just worried about mixing up such a large batch (worried about the heat). Though to be honest, i have never mixed up a batch with a bunch of aggregate in it, so maybe that will suck up some of the heat.

Yes it will however, how fast does this epoxy set?
Do you have a link to the product?

Jack

[Dan S]

Yes it will however, how fast does this epoxy set?
Do you have a link to the product?

Jack

http://www.systemthree.com/

I have both #2 and #3 hardner

[brunog]

Dan,
Don't worry about the mix heating too much don't forget the quantity of epoxy is only 10% of the total mix by weight or if you prefer about 20% by volume. the heat is being absorbed by the rocks.

Best regards
Bruno

[jhudler]

Dan, You'd want to use the #3 hardener to keep the viscosity down. To add to Bruno's comment, no one has reported any signs of exothermic runaway.
By volume that 1/2 gallon plus hardener (2:1) will yield 3.75 gallons or ~85 lbs using the current EG formula.
If you use lead shot then you calculate your yield from space your filling with epoxy; which is ~38% (62% packing density). Roughly; the 96 oz of epoxy on hand would be 96 * 3 = 288 fl/oz of epoxy/lead shot. Lead shot is ~500 lbs per cubic foot and 288 oz would be 0.30078 cu/ft = 500 * 0.30078 = 150 lbs of epoxy lead.
Might try a mixture of 00 and BB to get a higher density.

Jack (warning this is a late night post... use at your one risk )

[Eson]

Are you trying to build something like a Hexagide?
http://www.indoor.flyer.co.uk/kinematic.pdf (third picture or so)

I was thinking of a 'normal' hexapod because of the simple design, however i wonder if the ballscrews are so rigid and was thinking of stabilize them. Might be a good start anyway.
http://hem.bredband.net/b235625/hexapod.jpg

[jhudler]

I was thinking of a 'normal' hexapod because of the simple design, however i wonder if the ballscrews are so rigid and was thinking of stabilize them. Might be a good start anyway.
http://hem.bredband.net/b235625/hexapod.jpg

The hexapod or Stewart platform, is an inherently rigid system.
You do not need to stabilize them.
The rigidity comes from the size of the ballscrews, which is calculated based on the design loads the system will take.

Jack

[jhudler]

Wow a idea just smacked me face or it's an obtuse day...

You can take 6 screws and place them in 6 tubes (a little shorter then the screw) and fill it with a mixture of a Moglice type of EG. Wouldn't want to use Moglice here, it would cost a fortune.

To use Moglice for this, you could try spraying >20 coats of PVA on a screws and then cast it in EG. The do the last casting with Moglice. 100 grams of Moglice should be more than enough! You could literally pour the Moglice in the screw tube (the other end was cast closed) and screw it back into the tube and allow the hydraulic pressure to push the Moglice back up and around the threads.

The initial mold would have to incorporate something to align the screw parallel with the tube and that alignment aid would have to cast in place and for the final coating with Moglice so that all the threads would get an equal coating.

Jack

[brunog]

Wow a idea just smacked me face or it's an obtuse day...

You can take 6 screws and place them in a tube (a little shorter then the screw) and fill it with a mixture of a Moglice type of EG. Wouldn't want to use Moglice here, it would cost a fortune.

Jack,
someone mentionned a few posts back to make an epoxy/zeeosphere putty.

Would this be applicable instead of Moglice, perhaps add a small quantity of Teflon powder(or graphite is less expensive) to make it more wear resistant??

BTW Eson you have a cool project in mind!

Best regards

Bruno

[greybeard]

Er,one tube, or do I misread your idea Jack ?
Universal joint at the top and bottom of each leg ?
John

[jhudler]

Bruno, That would certianly make a good Moglice substitute. My only concerns are the hardness of zeeospheres acting as an abrasive. The addition of teflon powder might mitigate this.
Molybdenum powder might be better. I think Moglice is mostly Molybdenum Disulphide powder; just a guess, I've never seen a MSDS on it to know.

[jhudler]

John,
See picture. The cap's on the end could contain a divot or kinematic point that would help align the screw in the center. You would have to make a fixture to fix the tube parallel with screw and apply enough force to seat the screw in the divot.

This fixture would have to be small enough to fit in the cooker for post cure.

Jack

[jhudler]

I've got to get me some Moglice, the last time I saw this stuff was 18 years ago.