Expensive Lock Gates

[bag 'o' bones]

I was sitting on a bench the other day that appreared to be made of wood but was in fact some sort of (recycled?) plastic.

 

Considering oak locks gates cost around 25k to replace and only last between 15-30 years (I think I read somewhere), I was wondering what other materials other than steel have been tried that are better value in terms of what they cost versus their serviceable life?

 

I've heard they can turn old tires into all sorts of materials these days - rubber lock gate anyone?

[Dyad]

Or out of recycled pipe fenders dropped in the cut

[Jerra]

I've heard they can turn old tires into all sorts of materials these days - rubber lock gate anyone?

Might be a good idea for those who charge at the gates like the PIper boat. It could bounce them back down the lock.

 

Being serious if anyone made recycled blocks big enough lock gates with replaceable parts for where they get worn by boats rubbing could be a good idea.

 

We were looking for garden furniture earlier this year and found some which looked and felt like wood but turned out to be recycled plastic.

[dmr]

The canal is a huge piece of history and many locks are listed structures. English Heritage also (I believe) have a say in how locks are repaired. You can't just "modernise" it.

My own view is that if a plastic looked and felt almost like the original, and was much more cost effective, then it would be worth investigating, but that is the slippery slope!..

 

Hardwood is a very good material and not easily beaten.

 

................Dave

[ditchcrawler]

As an IWA branch we wanted to erect a seat in memory of a member who left money to help with the Ipswich to Stowmarket Navigation. As it was on council owned land we contacted them for preferred suppler. They informed us they had stopped using plastic (Wooden) benches for several reasons

[Jerra]

They informed us they had stopped using plastic (Wooden) benches for several reasons

Did they tell you the reasons. I would be interested to know.

[Scholar Gypsy]

The Environment Agency have been using recycled tyres as fender strips on some of their Nene and Ouse locks for a while.

 

We chatted with a couple of their contractors who were installing some last year. They said it was quite an unforgiving material ie you had to cut it exactly to the right shape and size, less flexible than timber, and a bit less forgiving if it gets hit. This is the sort of problem that can result, I think.

[Paul C]

I was sitting on a bench the other day that appreared to be made of wood but was in fact some sort of (recycled?) plastic.

 

Considering oak locks gates cost around 25k to replace and only last between 15-30 years (I think I read somewhere), I was wondering what other materials other than steel have been tried that are better value in terms of what they cost versus their serviceable life?

 

I've heard they can turn old tires into all sorts of materials these days - rubber lock gate anyone?

 

Does the £25k include its value for recycling?

[peterboat]

As an IWA branch we wanted to erect a seat in memory of a member who left money to help with the Ipswich to Stowmarket Navigation. As it was on council owned land we contacted them for preferred suppler. They informed us they had stopped using plastic (Wooden) benches for several reasons

I was at the coast today and sat on a 12 year old recycled plastic bench still looked like new I thought the brass plaque said 2013 but no 2003 it had fared worse than the bench

[magpie patrick]

The Cotswold Canal have a plastic swing bridge so lock gates are not impossible, but getting the material to withstand the forces is the challenge - the load on a lock gate exceeds the load on a swing bridge by a factor of ten or more, and bending is much less acceptable in a lock gate.

 

English Heritage/The local planning authority conservation officer only get a say if the lock is listed, and Heritage Lottery Fund only get a say if they are paying. wooden gates tend to be favoured because they give whereas steel ones bend out of shape, and because wood is naturally bouyant compared to steel. However, there is now some recognition, at least on non-crt waterways, that steel has benefits where locks won't see much use. The life of a wooden gate is around 25-30 years whether or not the lock is used much, a steel gate on a lightly used waterway might last 100 years.

 

Add to this the number of trees needed to make wooden gates (around 12 for one narrow lock) and that the gates decay faster than the trees to build them grow and the advantages of non-wooden alternatives become apparent when there is less operational need for wood.

 

HLF have approved steel gates on the Monmouthshire Canal in Cwmbran, these are also made in kit form so they can be assembled on site. I'll see if I can find some pictures...

[Jerra]

The Cotswold Canal have a plastic swing bridge so lock gates are not impossible, but getting the material to withstand the forces is the challenge - the load on a lock gate exceeds the load on a swing bridge by a factor of ten or more, and bending is much less acceptable in a lock gate.

Might it be possible to cast (mould) some form of strengthening in? Girders? That would still leave a gate looking like wood and more maintenance free.

[RLWP]

Go for a trip round Bradley workshop where they make the gates using carbon neutral wood, specialized equipment and traditional skills. Then investigate what has happened on the several occasions when new ideas have been tried on these highly refined wooden gates

 

Richard

[Jerra]

Go for a trip round Bradley workshop where they make the gates using carbon neutral wood, specialized equipment and traditional skills. Then investigate what has happened on the several occasions when new ideas have been tried on these highly refined wooden gates

 

Richard

However the gates under discussion wouldn't be highly refined wooden gates they would be highly refined modern material gates.

[RLWP]

However the gates under discussion wouldn't be highly refined wooden gates they would be highly refined modern material gates.

 

Which would be an improvement because...

 

Richard

[Jerra]

 

Which would be an improvement because...

 

Richard

Because the material last more than 30 years and would need less maintenance at the very least no painting every few years.

[MtB]

I was sitting on a bench the other day that appreared to be made of wood but was in fact some sort of (recycled?) plastic.

 

Considering oak locks gates cost around 25k to replace and only last between 15-30 years (I think I read somewhere), I was wondering what other materials other than steel have been tried that are better value in terms of what they cost versus their serviceable life?

 

I've heard they can turn old tires into all sorts of materials these days - rubber lock gate anyone?

 

 

I'd be reasonably confident in saying the vast majority of that £25k goes in surveying the worn out gates, designing the new ones, removal and disposal of the old ones, transport of the new ones to site and the fitting and fettling of them to hold water.

 

I doubt there would be more than a couple of grand saved by using plastic instead of oak as the manufacturing material. Possibly no saving whatever in fact, given the higher cost of working with recycled plastic.

Especially as Bradley Workshops are very well tooled up to make from timber, and tooling to build bespoke lock gates from plastic would probably set CRT back quite a few £million.

[Jerra]

 

 

I'd be reasonably confident in saying the vast majority of that £25k goes in surveying the worn out gates, designing the new ones, removal and disposal of the old ones, transport of the new ones to site and the fitting and fettling of them to hold water.

 

I doubt there would be more than a couple of grand saved by using plastic instead of oak as the manufacturing material. Possibly no saving whatever in fact, given the higher cost of working with recycled plastic.

I will admit to not knowing much about lock gate replacement so can you answer a few questions?

 

Surveying. What sort of survey is needed?

Designing new ones. Won't they be built to the same design as the ones they are replacing, after all presumably they have work efficiently in the past?

In this day and age will there not be records of sizes and design of gates? They must all have been replaced in the last 30 years (wooden ones that is).

[MtB]

I will admit to not knowing much about lock gate replacement so can you answer a few questions?

 

Surveying. What sort of survey is needed?

 

 

Measuring the lock accurately to see how much (if at all) the masonry has moved in the last 25 years.

 

(Have you SEEN how many CRT bods are needed for a twsk like this?!)

 

 

 

 

Designing new ones. Won't they be built to the same design as the ones they are replacing, after all presumably they have work efficiently in the past?

 

 

This, you being a clever bloke, will appreciate depends on the result of the survey.

 

 

 

In this day and age will there not be records of sizes and design of gates? They must all have been replaced in the last 30 years (wooden ones that is).

 

 

Indeed there will. And imagine if there was a minor (or major) flaw in the design of the old gates which CRT replicated in the new gates, by failing to design it out. Or if the just made identical gates to the old ones without considering if any changes were needed for any reason whatsoever. How much excoriation on here would they suffer?

 

I can see you're not from an engineering background!

[Jerra]

 

 

Measuring the lock accurately to see how much (if at all) the masonry has moved in the last 25 years.

 

(Have you SEEN how many CRT bods are needed for a twsk like this?!)

 

 

 

 

 

 

This, you being a clever bloke, will appreciate depends on the result of the survey.

 

 

 

 

 

Indeed there will. And imagine if there was a minor (or major) flaw in the design of the old gates which CRT replicated in the new gates, by failing to design it out. Or if the just made identical gates to the old ones without considering if any changes were needed for any reason whatsoever. How much excoriation on here would they suffer?

 

I can see you're not from an engineering background!

It isn't a question surely of how many go it is a question of how many are needed.

 

Thanks for the compliment, but surely the movement6 of masonry will either be small requiring a, little resizing or large requiring structural alterations to the masonry.

 

These locks have been around for a few years now (deliberate understatement) surely any design problems have been spotted and rectified in the 6 or 7 sets of gates that have been in place.

 

You are right I am not from an engineering background but your suggestions don't seem to me to hold water (pun intended).

 

So really what you are saying is IMO (worthless I know) is that there might be some minor changes in size compared to the last set.

[MtB]

 

So really what you are saying is IMO (worthless I know) is that there might be some minor changes in size compared to the last set.

 

 

Yes.

 

And checking for, and taking into account, those minor changes (IF they turn out to be minor, on checking) is a major cost factor. If new gates to the old dims won't fit, red faces all around. I mean, like, did nobody check FFS??!

 

As is removing the old gates, disposing of them, transporting the new ones to site, craning them into place and fettling them to fit..

 

I notice you think the same machinery that makes wooden gates can make plastic gates. BIG MISTAKE...

[magpie patrick]

 

 

Yes.

 

And checking for, and taking into account, those minor changes (IF they turn out to be minor, on checking) is a major cost factor. If new gates to the old dims won't fit, red faces all around. I mean, like, did nobody check FFS??!

 

As is removing the old gates, disposing of them, transporting the new ones to site, craning them into place and fettling them to fit..

 

I notice you think the same machinery that makes wooden gates can make plastic gates. BIG MISTAKE...

 

There is a big set of lock gates acting as a sculpture at start of the Droitwich Barge Canal: they were made for the Glasson Branch and didn't fit...

 

The interest in steel gates for the Monmouthshire Canal is because the gates will see relatively little use - when a lock is heavily used wooden gates are very durable, in the course of 25-30 years steel or concrete gates (yes, they have been tried) will have taken a hammering on a busy waterway and will need replacing. However on a quiet canal wooden gates rot at the same rate whilst steel ones just sit there doing nothing.

 

There have been many attempts to make lock gates cheaper/easier to maintain - they've nearly all failed

Edited September 21, 2015 by magpie patrick

[gazza]

The Cotswold Canal have a plastic swing bridge so lock gates are not impossible, but getting the material to withstand the forces is the challenge - the load on a lock gate exceeds the load on a swing bridge by a factor of ten or more, and bending is much less acceptable in a lock gate.

 

English Heritage/The local planning authority conservation officer only get a say if the lock is listed, and Heritage Lottery Fund only get a say if they are paying. wooden gates tend to be favoured because they give whereas steel ones bend out of shape, and because wood is naturally bouyant compared to steel. However, there is now some recognition, at least on non-crt waterways, that steel has benefits where locks won't see much use. The life of a wooden gate is around 25-30 years whether or not the lock is used much, a steel gate on a lightly used waterway might last 100 years.

 

Add to this the number of trees needed to make wooden gates (around 12 for one narrow lock) and that the gates decay faster than the trees to build them grow and the advantages of non-wooden alternatives become apparent when there is less operational need for wood.

 

HLF have approved steel gates on the Monmouthshire Canal in Cwmbran, these are also made in kit form so they can be assembled on site. I'll see if I can find some pictures...

All of the vee gates on the Nene and Great Ouse are steel. When you say not much use what do you mean?

I can't remember the last time a gate was replaced, our nearest lock at Wadenhoe had a counter fitted a few years ago, it's up to 15k + now.

[FadeToScarlet]

All of the vee gates on the Nene and Great Ouse are steel. When you say not much use what do you mean?

I can't remember the last time a gate was replaced, our nearest lock at Wadenhoe had a counter fitted a few years ago, it's up to 15k + now.

I suspect they're hit by boats a lot less.

 

Certainly some of the Nene gates have dates in the 1970s welded onto them.

[Jerra]

As is removing the old gates, disposing of them, transporting the new ones to site, craning them into place and fettling them to fit..

 

I notice you think the same machinery that makes wooden gates can make plastic gates. BIG MISTAKE...

I am well aware of the cost that would be run up removing and bringing the gates particularly at the more rural sites.

 

I am not sure where you got the idea that I think it will be done by the same machinery. Coming from a long line of woodworkers (my Dad was a wheelright) I am aware of what working wood is like. I have also had a tiny bit of experience in working plastics so no I don't think the same machinery will be used.

 

The way technology is changing they could probably be printing them on site in a decade or so.

[gazza]

I suspect they're hit by boats a lot less.

 

Certainly some of the Nene gates have dates in the 1970s welded onto them.

I think there are many locks on the Great Ouse that retain there original gates from the 60's onwards when navigation was reestablished upstream.

 

As I say, I'm 36, and with the exception of rebuilding Higham and Wellingborough locks to conventional vee gates both ends I can't think of any other locks that have had the gates replaced, or look likely to need them replacing in the near future.

 

Whether they are hit less is a moot point, there have been a fair few tossers transiting the Nene to the Ouse this year