Expansion Plate Mechanism

[Brad LeeParticipant @bradlee58914]

Currently working on a expansion plate mechanism to secure the inside of a pipe. Decided on an a general design similar to this pulley expansion plate but instead driven by a motor however I've hit a wall with determining a secure enough means to halt the pistons movement once its adjusted to the pipe's walls.

Any thoughts and suggestions would be very much appreciated.

[Brad LeeParticipant @bradlee58914]

[not done it yetParticipant @notdoneityet]

Drive the pink wheel with a worm gear which will not drive backwards? Just like Fordson Standard tractors.

Or fit a brake unit on the drive shaft?  Like an overhead crane, for instance?

Edited By not done it yet on 06/03/2018 16:23:43

[Jeff DaymanParticipant @jeffdayman43397]

Is this for a home workshop project or is it for work?

[larry PhelanParticipant @larryphelan54019]

Not many projects like this found in a home workshop.

[Brian WoodParticipant @brianwood45127]

Hello Brad,

A slipping clutch might meet your needs and prevent it locking up. I believe these are available and can be set to a given torque at which it slips; I suggest some research on those lines.

A neat design by the way but I think the wear element in the slots and/or the pins might become a problem if it is used frequently.

Welcome to the Forum too, there may well be other ways of doing what you want, those are my thoughts for what they are worth

Regards

Brian

[Brian Sweeting 2Participant @briansweeting2]

How big is the pipe?

Size matters when you are looking for a solution.

Is there a fluid inside the pipe?

More data required please, we can't see from here.

[not done it yetParticipant @notdoneityet]

“ Not many projects like this found in a home workshop.”

There might be if your workshop is a room for a 3-D printer!

[David George 1Participant @davidgeorge1]

I worked on a similar piece of equipment for a local plastic pipe manufacturer and we expanded the pipe into a ring weld jig for gas and water. The segments were expanded with hydraulic fluid pumped into the small pistons with a hand pump which they already have for welding pipe lengths together.

David

[not done it yetParticipant @notdoneityet]

Hydraulics are a far better solution. If the pipes are not round or there is foreign material at any would-be contact point, the design, above, fails to deliver.

[Anonymous]

Looks like an undergraduate design exercise?

Andrew

[Ian PParticipant @ianp]

Posted by Andrew Johnston on 06/03/2018 20:49:21:

Looks like an undergraduate design exercise?

Andrew

Well its more an opinion than a question but it is one possible scenario.

The only thing that make me curious is what 'secure the inside of a pipe' means. The insides of most pipes is already secured to the outside.

I suggest that we 'all' wait until the OP returns. There is no member profile so it is really pointless us all adding to the thread and speculating.

Ian P

[Paul LousickParticipant @paullousick59116]

Hi Brad,

Just some comments on the design.

The rotation angle appears to be about 15-20 degrees, so not much mechanical advantage to push the segments out and the pins in the slots are small so will not be able to withstand much of a load. The small contact area is small and wear will be a problem.

An alternative solution is to use a taperred pin to push the segments apart. This would also be self locking and could be pushed/pulled by a screw or air (or hydraulic) cylinder.

The outer segments will need a guide of some sorts to keep them aligned and not twist.

Cheers, Paul.

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Ian P on 06/03/2018 21:25:54:

The only thing that make me curious is what 'secure the inside of a pipe' means. …

.

Defend it against invaders, or escapers !!

The device is the radially symmetrical equivalent of a portcullis.

MichaelG.

[Brad LeeParticipant @bradlee58914]

Really appreciate the feedback from you all. Sorry for the late response to the thread. I’ve been caught up with assignments.

Good guess Andrew, this is for an undergraduate design task for my final year group project. Couldn’t imagine anyone building this let alone in their home workshop.

We’ve been tasked with creating a pipe inspection & repair robot. My task is to develop a stabiliser at the repair end of the robot. It’s main job is to secure the robot within the pipe during repair from vibration/shock/slip, hope that clears up what I said about securing the inside of the pipe. (can't seem to attach the image so here's a link https://i.imgur.com/Mvzr69f.png )

Ideally the pipe should operate in dry and wet conditions (in case some water remains when it’s emptied). It’s arms should also expand to 690mm from 350mm.

I initially thought to use a self locking (worm gear) motor with an encoder and it’s directional axis & plane corrected with a bevel gear. However, “not done it yet” quite rightly pointed out that each piston won’t move independently, inhibiting the overall function entirely.

Another thing I failed to give much consideration, is allowing enough room in the centre for cables and such to pass through.

So basically I’m pretty screwed. With a hydraulic design however, how would that fit these requirements and overall design.

Again thanks for taking the time to share your thoughts.

[Grindstone CowboyParticipant @grindstonecowboy]

Bit of lateral thinking.. how about an inflatable rubber bladder?

Regards,

Rob

[Dod MoleParticipant @georgeclarihew]

Idea

A cone with 3 equally spaced half round grooves which legs sit, threaded up the centre, motor driven screw to pull cone towards motor thus expanding the legs to contact pipe walls giving 3 solid points of contact with spaces between legs for cables, hydraulic/ pneumatic services.

Obviously needs more thought put in before put into practice i.e. insertion and retreival etc.

[KWILParticipant @kwil]

**LINK**    

Here is one way.

Edited By KWIL on 07/03/2018 19:56:25

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Brad Lee on 07/03/2018 18:43:30:

… My task is to develop a stabiliser at the repair end of the robot. It’s main job is to secure the robot within the pipe during repair from vibration/shock/slip, hope that clears up what I said about securing the inside of the pipe.

[ … ]

Another thing I failed to give much consideration, is allowing enough room in the centre for cables and such to pass through.

.

Would three radial struts suffice, I wonder

MichaelG.

.

I see that George beat me to it. 

Edited By Michael Gilligan on 07/03/2018 19:57:36

[Neil WyattModerator @neilwyatt]

Make it like a pair of car jacks at 90 degrees to each other – or use 3 cantilevers perhaps instead of 4?

[Anonymous]

Posted by Ian P on 06/03/2018 21:25:54:

Posted by Andrew Johnston on 06/03/2018 20:49:21:

Looks like an undergraduate design exercise?

Andrew

Well its more an opinion than a question but it is one possible scenario.

Any questions? And that is definitely a question.

Brad: It is well worth taking note of the post by Paul Lousick. The geometry of the curved slots is all wrong; they won't provide much radial force as modelled. They need to be more circumferential rather than radial. I'd probably use a multi-lobe cam and accept less radial movement. It might even be self-locking.

Not sure why there are comments about building it in the home workshop. Whether you'd want to build it is one thing, but it would be perfectly possible to build it in a home workshop.

Andrew

[Neil WyattModerator @neilwyatt]

Posted by Neil Wyatt on 07/03/2018 20:14:06:

Make it like a pair of car jacks at 90 degrees to each other – or use 3 cantilevers perhaps instead of 4?

I take it back,. Use a decent sized stepper and the gearbox is an unnecessary complication.

[Martin ConnellyParticipant @martinconnelly55370]

Why reinvent the wheel? Pipe bevelling machines have been doing this for years. They use three blocks with a tapered side pushed out by a tapered mandrel. This gives high mechanical advantage, self centring and simplicity. See the link below for examples of these machines.

**LINK**

Martin C

[HopperParticipant @hopper]

Posted by Martin Connelly on 08/03/2018 09:39:39:

Why reinvent the wheel? Pipe bevelling machines have been doing this for years. They use three blocks with a tapered side pushed out by a tapered mandrel. This gives high mechanical advantage, self centring and simplicity. See the link below for examples of these machines.

**LINK**

Martin C

Blimey what a world we live in today. We used to do whole power-stations full of pipe ends with angle grinders. Would have killed to have one of these gadgets. Absolutely brilliant. And as you say, simple as.

[Author]

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