Epoxy-Granite machine bases (was Polymer concrete frame?)

[jsage]

Martinw,

Just curiousity. Yes, my orientation was about 3 hours of gore (lower case). Referred to as stinky vacs (old). Typically the specs (negative pressure) were expressed in MB. Basically meaningless to me. If I remember correctly atmospheric is 17 psi so that sounds pretty good.

Have to pick up one of those books.

Mike

[ger21]

14.7psi

[jsage]

Ok Ger21,

You got me, I'm not from this planet ; )

[martinw]

14.7psi

Dear jsage,

Gerry is spot on.

To relate to other units, here are a few more conversions

One atmosphere=14.7psi=1 bar=1000mB

Best wishes

Martin

[jsage]

I know he is. I just have 17 stuck in my brain. Though I'd swear I'd seen 17 before. Thus the joke. Either time has effected my memory of it, likely. Or perhaps I was thinking of maximal clamping pressure, unlikely. Second time I have made that error. 6 years from now I'll probably say 17 again ; )

[davo727]

Well, Cosmetically its not beautiful but it is definitely functional. I found that the best thing for sealing up gaps between the frame and base was a mix of 5 minute epoxy and sand. Once I had the gaps all sealed up I started mixing up batches of the main course. OK starting weight of base 100 lb. Steel frame 15 lb. Completed weight 180 lb. So 65 lb of epoxy, sand, rock mix. The following weights are approximate- Sand 17 lb, rock 38 lb and epoxy 10lb. So that gives us about 55 lb of filler and 10 lb of epoxy. When I was mixing it I was going by volume case I didnt have a small scale to use. I found that 1 part epoxy, 1 part sand and 3 parts rock was user friendly and had good wet out of the filler. One bucket batch I tried with 4 parts rock and it was too dry, not enough epoxy. There were a lot of gaps between the rocks and it would not have bonded together well like that so I added some epoxy to get it to the consistency of the other batches. With about 1/4 or 5/16 of an inch to go on the fill I ran out of rock and mixed up some sand and epoxy to try and finish up. After I had poured it in and smoothed it out that batch had a lot of tiny air bubbles in it floating on top. I didnt have that problem with the other batches with rock mix. Anyway I guess I should have squeegeed the bubbles off the top before I left for 1.5 hrs. When I got back it was kind of rubbery so I scraped all the soft tiny bubbly crap off the top and now the rest is really hardening up good on its way to being a big old happy rock So one thing I think is mixing up a batch with epoxy and just fine sand you may have a problem with air bubbles. The rock mix did not have that problem. The average weight ratio of epoxy to filler on this was about 1 to 5.5. With the materials I used here adding much more percentage of filler was going to cause a dry and bad mix. In the pics here part of the fill looks wet but its not. When I slid the base off the bench by hand to weigh it I was like holy crap! I used my hoist to put it back on the bench Dave

[davo727]

Oh one more thing- When the mix was curing it just barely got warmer than ambient maybe 10 or 15 degrees warmer than the temp here of about 75 this afternoon. The fill on this base is in 3 sections and I estimate the mix weight of the 2 long sections about 25 lb each and 15 lb for the square section. I did this all at once without stopping so its good to see there was no problem with overheating when curing the large amounts of epoxy. Dave

[walter]

Nice work Davo!

I think we may need to go with Larry's suggestion ("Removing entrapped air with a blow torch...")

That reminds me, I need to buy a fire extinguisher.

[davo727]

Thanks Walter. Yeah and maybe do a flammability test with a small sample of epoxy outside and see what happens. I would hate to turn my project and the garage into an inferno. D

[jsage]

I don't know if anyone mentioned this but I've heard of using quartz lamps or something similar. The application was for post cured epoxy. Probably gentler on the Epoxy. I believe the slower the cure the better the characteristics. Just enough to promote the outgassing.

[lgalla]

("Removing entrapped air with a blow torch...")
Walter you forgot the smilies.Actually the blow torch thing is mainly for the surface plate or thin sections, not for heating batches.If you need to lower the viscosity put the mix container in a tub of hot water.If trying the torch you move quickly over the surface.BTW a paint stripping gun works also.To quote Walter "nice work Dave"
The rock batches naturally released air faster as the spaces are greator.A cheap air hammer may be a good vibrator.
Sandi, Quartz is a slavic word.
Bruno thanks for the link.I once wanted to say what we need is right under our noses.US silica and LV Lomas are good to deal with and offer bagged dry material.Some of the big guys only sell railcar loads.I think Lomas is also in Montreal and they have no problem with samples or one bag orders.
Larry
Quartz crystal sweeper

[lgalla]

Atenman1 I think you posted a concrete vibrator source many many posts ago.Do you still have it?Harbour Freight has one for about $80 and there are other types on E-bay.Apparentally 30 seconds with one of these type units is enough for concrete compaction and air removal.
Larry