Is teflon a good material for conduction

[Mathijsgri]

I have designed a gangway for a schoolproject, the gangway made in 2 parts the second part can retract in the first part. The total length is 35 meters, I'm looking for aan good way to make the two parts go smooth in an out eacht other. I was looking into Teflon and what i thought it was a excellent material but no other gangway in the offshore makes use of this system and I'm an wondering if I'm missing why it won't work.

Does anyone have any experience with Teflon? in the accement you find a screenshot of the design.

 

[berkeman]

I have designed a gangway for a schoolproject, the gangway made in 2 parts the second part can retract in the first part. The total length is 35 meters, I'm looking for aan good way to make the two parts go smooth in an out eacht other. I was looking into Teflon and what i thought it was a excellent material but no other gangway in the offshore makes use of this system and I'm an wondering if I'm missing why it won't work.

Does anyone have any experience with Teflon? in the accement you find a screenshot of the design.

I'm guessing that by "conduction" you mean sliding with low friction? (Not thermal or electrical conduction) Is that right?

And don't you already have roller wheels or bearings to allow the two sections to slide in and out of each other?

 

[Mathijsgri]

Yes i mean sliding, and no i use teflon blocks. maybe it makes more sense in the picture. the brown stuff is teflon, the teflon will enclosed, the second part of the bridge has a kind of traingle made of steel on the bottem, that way the steel traingle let's the gangway slide in and out.

 

[Mathijsgri]

some more screen shots maybe this help, the first picture with the brown teflon on it is the first part, the second part(picture 2 with the blue things) slide in part 1 .

 

[berkeman]

Yes i mean sliding, and no i use teflon blocks. maybe it makes more sense in the picture. the brown stuff is teflon, the teflon will enclosed, the second part of the bridge has a kind of traingle made of steel on the bottem, that way the steel traingle let's the gangway slide in and out.

I can see some potential problems with trying to use sliding across teflon blocks like that. This is exposed to the weather (rain, soot, smog, diesel exhaust, etc.), right? Even if clean teflon may have a moderately low coefficient of friction μ, dirty teflon most likely would not.

That's why the traditional method of using roller wheels (with the bearings fairly sealed up from the environment) is generally used. Have you tried mocking this up for some experiments? (not the whole truss, just some experimental parts of it all...)

 

[Mathijsgri]

no I haven't expiremented with it. How this gangway will be used is you slide it to a platform offshore, it will fasten on the platform due to waves and wind it will slide 1 meter in and out on average. I don't think dirt is a very big problem. and my problem with bearing or wheels is that teflon can handle exstreem compression so you don't need that much surface to deal with the mometum in the center.

 

[Mathijsgri]

The brigde has a mass of 23000 kg so the mometum will be huge in the center. if you use wheel or something the overlap between the two parts must be bigger right? so with teflon you need less overlap so less mass less espensive. Is this true?

 

[berkeman]

no I haven't expiremented with it. How this gangway will be used is you slide it to a platform offshore, it will fasten on the platform due to waves and wind it will slide 1 meter in and out on average. I don't think dirt is a very big problem. and my problem with bearing or wheels is that teflon can handle exstreem compression so you don't need that much surface to deal with the mometum in the center.

I'm sure you've looked at existing designs as part of this project. How are these gangways typically designed for the in-out movement?

 

[Nidum]

You very likely need more guideways than just the two shown .

Think about how to establish a moment connection between the two gangway sections .

Probably easier to use wheels and tracks than plain slides .

 

[berkeman]

23000 kg

Your 35m gangway has a mass of 23000kg?

 

[Mathijsgri]

Your 35m gangway has a mass of 23000kg?

yes

 

[Mathijsgri]

You very likely need more guideways than just the two shown .

Think about how to establish a moment connection between the two gangway sections .

Probably easier to use wheels and tracks than plain slides .

two on the bottem and two in top.

 

[anorlunda]

You may not have dirt but you will have salt crystals. They are terrible for friction and sliding surface damage.

Hard nylon blocks are often used for sliding bearings. Pretty low friction and very good wear.

if I remember the name right, also a plastic named delrin.

Durability may be more important than friction.

 

[tygerdawg]

Plastic blocks for sliding elements whose total mass is 23,000 kg is a bad idea. The plastic may be slippery, but will not survive the bearing stress due to applied loads. Redesign with roller bearings. For such heavy structure, you should investigate steel wheels/casters (with bearings) riding on steel guide rails. This is how overhead crane carriages and other heavy equipment is moved around. You've got a lot of calculations in front of you, and also a lot of liability you must manage.

 

[Baluncore]

Where the steel shaft of a water mill ran in wooden bearing blocks, the steel shaft wore out first as grit became embedded in the wood. Likewise, fine grit will be pressed into the Teflon or plastic blocks. The grit will then wear the material of the rail that runs on the exposed plastic blocks.