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

1. Originally Posted by fyffe555
Twisting forces are somewhat different from a simple deflection.

To answer the question; adding E/G doesn't appear to resist torsion or twist by any more than the tube alone would.

Andrew
Dear Andrew,

I hope I have not misunderstood.

I can't back this hunch up with calculations , (wish I could) , but IMVVHO, adding E/G to fill a hollow steel section will almost certainly increase its resistance to twisting.

Suppose you have a hollow steel box section. Suppose it is vertical, and you are looking down into the box. If you twist it, it will not deform into a perfect parallelogram, but some parts of the walls of the box will be closer together than before, and some will be further apart.

If you repeat the process with the box filled with a material which is strong in compression, surely it has to increase the section's ability to resist twist, even if the filler is weak in tension?

My 2 cents.

Best wishes

Martin

2. Originally Posted by martinw
Dear Andrew,

I hope I have not misunderstood.

I can't back this hunch up with calculations , (wish I could) , but IMVVHO, adding E/G to fill a hollow steel section will almost certainly increase its resistance to twisting.

Suppose you have a hollow steel box section. Suppose it is vertical, and you are looking down into the box. If you twist it, it will not deform into a perfect parallelogram, but some parts of the walls of the box will be closer together than before, and some will be further apart.

If you repeat the process with the box filled with a material which is strong in compression, surely it has to increase the section's ability to resist twist, even if the filler is weak in tension?

My 2 cents.

Best wishes

Martin
Mostly correct - but the E/G will only have an effect if the box does deform. If you take larry's example, adding E/G will have an effect only if compression of the core occurs - and even then it's not as strong as steel. If you have a tube of sufficient strength to keep defelction within the requirements of a machine, ie in the thousanths then the E/g filler will not get compressed and so add minimum strength.

The twist should reduce the cross section area and so compress any core, not put it in tension., which is good since E/g is much stronger in compression. But the E/G is still weaker than the steel around it an dthe peripheral tube will carry the majority of the load.

You could use a weaker tube and rely on compression of the core or greater core strength to contribute to the total strength - but why would you? Steel is a \$1 or even 0.50c a pound. E/G is more expensive.

E/G has it's place but you can't expect to do everything with one material.

3. [QUOTE=fyffe555;287890]Mostly correct - but the E/G will only have an effect if the box does deform. QUOTE]

Dear Andy,

Maybe I'm being stupid again.

If the idea of filling the box is to prevent deformation, and it has that effect....

I'm lost.

Best wishes

Martin

4. I think I got it.
You would not design a machine that relied on the modulus and compressive strength of E/G.Our tube is strong enough on its own and our E/G does what it does best,vibration damping in this case.
Larry

5. ## Found this on "Dynamic Stiffness.

http://www.engissol.com/Article2.htm

Still Working on Calculations.

6. Post deleted.

7. Originally Posted by ckelloug
Fyffe,

Are we sure that the compressive and tensile moduli are the same for E/G. ?
Based Report #6361 from the NIST the specs (page 3)are the following:

Density: 1950-2400 kg/m3

Linear shrinkage: .003-.05%

Compresive strength: 50-150 Mpa

Flexural Strength: 15-50 MPa

Tensile Strength: 8-25 Mpa

Modulus of elasticity in compression: 20-40GPa

Modulus of elasticity in tension: 12-15 GPa

Brinell hardness: 240-400 MPa

Grindability: .10-.30 cm

Poisson's ratio: .30

Linear thermal expansion 10-35 (1/K)*10^6

Water absorption: .02-1 %

Best regards

Bruno

8. Finally nice epoxy curing weather.No posts for 2 days.Walter and the other experimental guys are taking their epoxy blocks outside to enjoy the good spring weather and speed up the cure.Progress reports are fourth coming.
Larry

the thread is to big to all of it,

what resin can be mixed with water and concrete?

10. Eloid,

I'm the thread's newest participant but the idea is to use epoxy as the matrix to bind granite particles. It's called concrete because it has a matrix with embedded stones but in the discussion on this tread the stones are embedded in epoxy, not portland cement.

11. Yes the thread is to big or long to expect someone to read it all.I have been onboard since the start and find it difficult to remember everything.
Your reference to resin and water would be portland cement which we have discounted as not suitable for the purpose due to shrinkage and possibly rusting.Stick with epoxy.
Larry

12. Thank you for contacting us about your casting application. If you can
live
with the long set time, our CLR 1190/ CLH 6230 would meet your
requirements.
The data sheet is attached. Please let me know if it looks promising.

Do you know how much you might need for your application?

Best regards,

Barbara Zymiak

Technical Sales Support
Mississauga, Ontario
Tel: 905-673-0510
Fax: 905-673-0519
Toll-Free: 1-800-563-3769

-----Original Message-----
From: anonymous@cgi0.cgi0 [mailto:anonymous@cgi0.cgi0]
Sent: April 18, 2007 11:42 PM
Subject: General Inquiry

****************************************************************************
***
ProdType: Epoxy
ProductNo:
FirstName: larry
Do you have an epoxy for casting quartz sand/granite aggregates
mix.Pours
would be 1"to4" thick at a time.

The viscosity should be under 600cps and have no reactive dilutents.The
purpose is to damp resonances on machine tools

Thanks

Larry

I have not been sleeping on E/G but large corps E mailed have not responded.
Larry

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