pipe diameter increase

[willisZ]

Hi

This isn't a strictly engine question, but...

I have a pump device that pivots on a 1 1/4" pipe - a hollow PVC pipe acts as the socket that fits over the pipe about 5". But the pipe is just a little too small, so that the device rocks slightly.

So my goal is to wrap something around the pipe for a snugger fit. But I don't want to use duct tape for fear it will bunch up over time.

I'm thinking maybe a wide teflon tape wrapped around several times. very thin thickness and a smooth surface. But I haven't been able to find any wide teflon tape.

any suggestions?

thanks for your brain power!

Kip

 

[Jasonb]

It would help if you put a location into your details but if in the UK try this slick tape, should be able to find something similar elsewhere though

http://www.axminster.co.uk/axminster-slick-low-friction-material-prod21305/

J

 

[willisZ]

that's great! I've never heard of that kind of tape.

I'm in Michigan in the USA -

[after searching online]

Wow, that's pretty expensive! looks like 18 yrds in the shortest roll. I only need a couple of feet. maybe i can find some sheets of adhesive backed material instead of a roll of tape.

the only downside is that it's 1/32 inch (= 31 mils) might be too thick?? i bought some anyway...

{later}

I found this site that has 12" wide adhesive sheets - for less than $10 each
http://www.eplastics.com/Plastic/Slick_Strips/SLICKSTRIP0-030X12-000-PER-FT

Yeah!

 

[lampy]

We use a similar product at work, as far as tape goes it's very durable. Unfortunatley I don't know where we get it :-\

 

[RollaJohn]

Kip:

One thing to remember about pipe dimensions is that the outside diameter is fixed for a given pipe size. While the inner diameter varies with the various schedules to get the different pressure ratings.

By going to a higher pressure rated pvc pipe you may get the fit desired or need to bore or ream to match your 1 1/4 inch pipe.

 

[kvom]

I think that's reversed. Pipes are specified by ID, tubes by OD.

 

[Mosey]

Might it be possible to machine a fitting to adapt the 2 diameters for a snug fit?
A job for an amateur machinist?

 

[Mainer]

@kvom

No, 1/2" copper tubing is 5/8" od, and more or less 1/2" id.

As for pipe.... The way I heard it, pipe is specified by the id it used to be when pipe was first being made. Originally, 1" iron pipe was 1" id. It had to be thick because the iron wasn't very good and that was how they made the pipes strong enough. Over time, the quality of the iron (steel) in pipes improved so they could use a thinner wall for a given pressure rating, so they made the inside of a 1" pipe larger while keeping the same od for compatibility with existing fittings. Today, there is nothing about a 1" pipe that measures 1", but there used to be. (Not guaranteed correct, but it sounds plausible.)

 

[Jasonb]

PVC pipe has the same OD but the OD varies depending on its pressure rating C,D & E over here not sure how they spec it on your side of the pond. All the fittings are the same size and rated at the higher pressure.

J

 

[Mosey]

Pretty soon cast iron pipe, which is PVC, will be bamboo. Cool!

 

[dalem9]

Welcome Willisz .Were in Michigan Are you. Dale

 

[RollaJohn]

Nominal Pipe Size (NPS), a North American set of standard sizes, the pipe dimensions for 1 1/4 inch are:

1.660 in. outside diameter for all schedules

Wall Thickness for various Schedules:

SCH 5 0.065 in.
SCH 10 0.109 in.
SCH 30 0.117 in
SCH 40/STD 0.140 in.
SCH 80/XS 0.191 in.
SCH 160 0.250 in.
XXS 0.382 in.

The trick will be finding a supplier for the size you desire off the shelf.

 

[willisZ]

Daelm, I'm in Farmington.

I went ahead and bought the 12" sheet of material. the only downside - it's 30 mils thick. might be too thick - that'll add about 1/16" wrapped all the way around the pipe just once. I was hoping for something more in the 5 mil range, so I could wrap it several times till the fit was perfect.

but I'm still looking for other, thinner sheet material.

The PVC pipe "socket" is already epoxied into the main structure - a 1.5" x 1.5" square aluminum tube, so I really don't want to have to try modifying it's I.D.

thanks for all your responses!

 

[GailInNM]

There are two places I know that adhesive Teflon tape are used that might provide a place to look locally for some scraps.

1. It is used for conveyor belt side liners to protect product damage when being transported. Think packaging transport belts for food packaging.

2. To cover the heating elements on heat sealing equipment for sealing poly bags.

There are two types of adhesives used on the tape. Acrylic and silicon. Silicon is more expensive and is normally used when things are subject to higher temperatures like on heat sealing equipment.

Wrapping multiple layers is not a good idea as it will not stick to it's self reliably. After all it is made to not have things stick to it. Consider using a thin layer of Teflon tape over a built up section made up of packaging tape or maybe even duct tape. But only one layer of Teflon tape butt jointed or even a small gap.

EBay has lots of tape from about 0.002 up to about 0.010 thick in various widths and thickness. Search on "teflon tape adhesive".

I have two rolls. One 0.003 thick x 3 inch wide and one 0.010 thick x 1 inch wide that I use for lining metal machined ignition boxes on engines so the high voltage stqays where it is supposed to be.

Gail in NM

 

[bearcar1]

Hi Willis, I'm still attempting to get my head around your problem. If I understand correctly, you basically have two pipes that fit over one another and they exhibit too much free play. Is that right? Now then, does the interface required need a seal of any kind or is it merely a slip fit and only needs to rotate? I guess that I am not understanding about the tape, teflon or otherwise usage to gain the size. Shim stock in Aluminum or brass is available in just about any thickness you can dream up. What amount of play do you need to take up exactly? Have you measured? Get a piece of shim the required thickness, wrap it around the inner pipe, cut so there is no overlap and use a contact type of adhesive to bond the shim in place. Best of luck.

BC1
Jim

 

[willisZ]

never heard of "Shim stock" - I'll look it up!

"Wrapping multiple layers is not a good idea as it will not stick to it's self reliably."
Gail, you're absolutely right (!) What was I thinking? :O

 

[willisZ]

I finally tried the Teflon material on the post and it's too thick - so I'll have to try a thinner mylar (?) or maybe just fill the gap with a thick grease??