Looking for PVC Experts

[rplace]

If I wanted to perfectly center a 2" PVC pipe inside a 5" PVC pipe what is out there in the PVC/plumbing world to help me accomplish this? My ultimate goal is to devise a mold for concrete where I end up with close to a 5" OD cylinder with a 2.25" centered through out it. It needs to be about 6" tall. From this chart:

 

 

I think the 5.016 ID of the 5" pipe is close enough and the 2.375 OD of the 2" pipe is also close enough. I figure I can cut the pipe to any length I want to arrive at the proper height of my finished project. So how would I center them and hold them in place while my casting of cement is drying? Do I need to do anything to the inside pipe to make it come lose from the cement once dry?

 

Any other thoughts on how to get a heavy, round cylinder with a hole throughout it welcomed.

 

Something along the idea of this. But 5" OD and a 2.25" hole throughout it:

 

 

[Pete H]

I've got to ask a few questions to better understand the finished product to see if I can offer anything useful.  Typically, forms are oiled up for easy removal but most of this will have to do with when you remove your mold and where the concrete is at in the curing process.

 

1.  What are you using these for?

2.  What is the final finish going to be?  Just concrete?

3.  What type of concrete are you planning on using?

4.  How exacting do your dimensions have to be?

5.  Can you do one long one of these (?) and then cut them with a concrete blade to the exact length you need?  

[DizRotus]

Is there an abstract of your concrete advice?

[CECAA850]

Are you going to have to pull the outside PVC pipe off also?  If so, the inside of the PVC pipe isn't as smooth as the outside and may be difficult to remove.

[CECAA850]

Do you own a Jasper Jig?  If so, centering and making the bottom plate would be a snap.

[billybob]

See that Mueller makes a 4inch by 2inch reducer. Someone may make  5x2 reducer or couple of reducer s to get there.

[USNRET]

Make the 2" PVC longer than you need (see step 3)
Use a mold release parting agent. You can fill inside the 5" PVC and then pour it out or pull a soaked rag thru several times. Wipe the OD of the 2"
Drill through the 2" pipe at a location where it has some strength (3-4" from end)
Insert a strong bolt thru the hole and use it to pull the inner pipe

Many ways to center the inner pipe with plastic / wood / rubber circles,  

[rplace]

I want to make a housing for the motor of my turntable. Currently VPI has SAMA that house a Hurst motor. They look like this.

 

 

and hold a motor like this. Note Round part is below square top plate

 

 

I have a SOTA Total Eclipse which is a drop in replacement for the Hurst motor Here is the link https://sotaturntables.com/products/total-eclipse-package/

 

I got the idea from many of these I have seen for tonearms.

 

So I want to make a cement version of the stainless thing VPI has.

 

Very much like the pictures in first link.

 

I measured my VPI one and it is right at 5" OD the hurst square plate is just about 2.25. If you check the SOTA link they have actual dimensions for the motor in a PDF. I currently have the Sota motor in the VPI base, so the measurements need to be close but not exact because the square plate can cover up a bit of the round hole for the motor.

 

 

[USNRET]

Oh, I thought you want feet long not inches. See if you can find / borrow one of these

https://www.globalgilson.com/cast-iron-concrete-cylinder-molds

 

[rplace]

19 minutes ago, CECAA850 said:

Do you own a Jasper Jig?  If so, centering and making the bottom plate would be a snap.

 

No, I cold probably get one if not super expensive, link?

 

33 minutes ago, Pete H said:

1.  What are you using these for?

2.  What is the final finish going to be?  Just concrete?

3.  What type of concrete are you planning on using?

4.  How exacting do your dimensions have to be?

5.  Can you do one long one of these (?) and then cut them with a concrete blade to the exact length you need?  

 

1 and 2 see above.

3, not sure yet I made a concrete counter top for my Big Green Egg it has lasted 5+ years...I'm looking into ShapeCrete right now.

4 close but not perfect

5 No

[babadono]

jasper jig

https://www.amazon.com/Jasper-200J-Circle-Cutting-Plunge/dp/B00009K77A

sure they must be available other than Amazon, google is your friend(?)

[Pete H]

9 minutes ago, rplace said:

 

No, I cold probably get one if not super expensive, link?

 

 

1 and 2 see above.

3, not sure yet I made a concrete counter top for my Big Green Egg it has lasted 5+ years...I'm looking into ShapeCrete right now.

4 close but not perfect

5 No

I'm just throwing this out there for your consideration.  Did you consider just having someone machine the piece out of a solid chunk of material?  I think your finished project will be perfect without any grief, with the exception of writing the check.  There are also a multitude of design options with casting epoxy that you could just pour it solid and drill out the center, this could be done with concrete as well if that's what you're set for on the finish.  

[rplace]

1 minute ago, Pete H said:

I'm just throwing this out there for your consideration.  Did you consider just having someone machine the piece out of a solid chunk of material?  I think your finished project will be perfect without any grief, with the exception of writing the check.  There are also a multitude of design options with casting epoxy that you could just pour it solid and drill out the center, this could be done with concrete as well if that's what you're set for on the finish.  

 

I'm not married to concrete, just figured easier and I'm familiar working with it. Where would I go to find a 5" piece of stainless that somebody would machine out the center for me? It needs to be fairly heavy and vibration free.

[rplace]

15 minutes ago, babadono said:

jasper jig

https://www.amazon.com/Jasper-200J-Circle-Cutting-Plunge/dp/B00009K77A

sure they must be available other than Amazon, google is your friend(?)

 

I've got a circle template for my router. Are you/Carl suggesting making a "plug" out of wood the ID of the PVC? Then another hole to center the inner pipe in? I could see that working. I was thinking that if I make the inner pipe longer it might aid in pulling the inside out.

 

And yes I need to end up with both pieces of PVC gone when I'm done. I'm looking into release agents now as @USNRET mentioned. Are they thick-ish like grease so you can coat the mold/pipe to prevent the cement from sticking?

[CECAA850]

6 minutes ago, rplace said:

 Are you/Carl suggesting making a "plug" out of wood the ID of the PVC? Then another hole to center the inner pipe in? I could see that working. I was thinking that if I make the inner pipe longer it might aid in pulling the inside out.

No.  Take something like 3/4" wood and router 2 circles about 1/4" into the wood.

[Pete H]

Just now, rplace said:

 

I'm not married to concrete, just figured easier and I'm familiar working with it. Where would I go to find a 5" piece of stainless that somebody would machine out the center for me? It needs to be fairly heavy and vibration free.

Time to call in an expert.  Hey @Dave A this is in your wheelhouse.  

 I don't think you're limited to metal either, you could look at quartz, granite, and many other materials that it could be fabricated from without going down the DIY path.  

[Rudy81]

Just make two donuts out of any material using your choice of circle cutter.  The inner hole cut the size of the inner pipe outer diameter.  The outer circle cut to the diameter of the inner size of the large pipe. Place both donuts on the pipe while the concrete sets. 

[rplace]

I'm thinking Carl's idea for the base. 3/4 scrap ply with routed "grooves" to hold both pipes. then Rudy's donut idea for the top. Place inner pipe, fill with concrete then put the donut/top on while it hardens.

[Rudy81]

10 minutes ago, rplace said:

I'm thinking Carl's idea for the base. 3/4 scrap ply with routed "grooves" to hold both pipes. then Rudy's donut idea for the top. Place inner pipe, fill with concrete then put the donut/top on while it hardens.

 

Rich, that should work.  Not sure what your project is, but if you need to remove the tube forms, I would recommend paper based tubes. This way, you could always dissolve the tubes with a little elbow grease and water.  If the pvc won't let go of the concrete, that may create a problem down line.

 

Never mind....helps if I read the entire post.

 

For your project, I might look at obtaining a suitably sized wood piece.  Say a rolling pin with the ends cut off.  Then, use a fosner bit on your drill press.  Take your time and go slow. Then you have a very nice sleeve for your motor, which can be stained or painted. Just my 2 cents.

 

If you can't find a suitable sized rolling pin or such, find a piece of lumber thick enough to cover the height of your motor.  Then, use the circle cutter to cut the outer diameter.  Then, back to the fosner bit for the inner diameter. 

[rplace]

7 minutes ago, Rudy81 said:

 

Rich, that should work.  Not sure what your project is, but if you need to remove the tube forms, I would recommend paper based tubes. This way, you could always dissolve the tubes with a little elbow grease and water.  If the pvc won't let go of the concrete, that may create a problem down line.

 

I was thinking of cardboard tubes made for pouring concrete in, but finding the right size would be a problem I think. Toying with the idea of cutting the outer pipe in half lengthwise and holding together with zip ties when removing two halves when dry....I'm sure there would be a seam though.

 

Maybe @Dave A will come along and has ideas on machining me something shiny. I like the idea of writing a check if I could get it made to specs and probably better end result.

 

Here is a shot of the TT plinth from above. There is not too much play for the ~5" outer diameter. This future motor housing has to fit in the "U" in the bottom of the plinth.