Cracked Instrument Casings

[Zulu10]

Whilst concluding my conversion to LED lighting on Sunday I got a nasty shock when I removed the instrument binnacle cover and found that all five of my minor gauges are exhibiting some degree of cracking.

 

The water temperature and fuel gauges being the worst; having cracks around more than 300 degrees of their circumference.

 

All this on a car that has done 20,000 miles hence has spent most of its life away from extremes of temperature.

 

The cost of replacement is obscene: £450 for five gauges, and I’m still awaiting ‘Speedy’ Cables’ quote for repair, but it occurred to me that either of these solutions will still leave me with the same weakness to future failure.

 

I’m therefore contemplating a modern alternative which is to have a casing 3D scanned as a baseline, then converted into a CAD file which can be modified to thicken the plastic to strengthen where appropriate, before being manufactured using 3D printing.

 

The non recurring expense of going for injection moulding rules it out unless there’s a demand for thousands, which I very much doubt, but I wonder what the potential interest might be for modified casings?

 

I’m aware that the same gauges are used in the Esprit, early Elise and some TVRs (anything else?) so I can’t imagine that I need to make a batch of more than 10 sets i.e. 50 cases initially.

 

Obviously I’d want to amortise my initial outlay in scanning and re-designing, but firstly I’d like to get a feeling for who would be interested, please?

 

Hopefully this doesn’t count as illicit marketing… but happy to be corrected.

 

 

[Choppa]

Unlucky, I've never heard of the gauge casings breaking like this before.

I'd be wondering  if, at some point in the past, a PO had tried to lever them out using a screwdriver under the black outer rim rather than taking the binnacle off and removing them like you are supposed to. Even so you'd have expected them to stop once they'd bu**ered up a couple of them.

I'd be tempted to try a bit of Araldite to repair the cracks on some of them before spending that sort of money on replacements. Even if you only successfully repair one of them you'll be quids in, and once refitted they shouldn't need to come out again any time soon.

[Zulu10]

Thanks Colin, but if you search this forum, other Lotus groups, and indeed any number of TVR forums (fora?) you'll see that it's a commonly mentioned problem.

I think that it's exacerbated by over-tightening of the knurled nuts that hold the mounting clamp.

I've tried glue but would prefer something more permanent....

[jonwat]

What about touring scrapyards for car with cars instruments with metal cases that you could cannibalise?  

[Zulu10]

2 minutes ago, jonwat said:

What about touring scrapyards for car with cars instruments with metal cases that you could cannibalise?  

Funnily enough that was my wife's suggestion - to replace plastic with metal - and I considered it, and also discussed it with an instrument repairer.

Unfortunately we concluded that the way each of the terminals is brought out of the back of the gauge - using a threaded stud - would mean that there would be a lot of re-work necessary to make insulating pillars for each stud.

I therefore discounted the idea for the time being.

At one point I also considered buying cheap Chinese gauges from AliEpress and cannibalising them just for their casings...

[tomcattom]

Are they the caerbont gauges? I gather this is not an uncommon issue with their plastic cases.

I believe @Chillidoggy may have had his dials refurbished by someone but I can't for the life of me remember who it was or find it in his build thread. Hopefully he'll see this and reply and tell us.

 

*EDIT* Sorry managed to skip over the line where you have already found the company that does the repairs. I think I need to go to specsavers!

[Chillidoggy]

They are Caerbont gauges, and yes, Speedy Cables did the refurb on them, including new casings. Definitely cheaper than new replacements, but they did take a long time to do.

In my opinion, the cases probably fail due to over-enthusiastic tightening of the securing screws, and/or knocking them when they’re in situ. They really don’t need to be that tight, but if you change them for another type, the originality has gone.

[Zulu10]

5 minutes ago, tomcattom said:

Are they the caerbont gauges? I gather this is not an uncommon issue with their plastic cases.

I believe @Chillidoggy may have had his dials refurbished by someone but I can't for the life of me remember who it was or find it in his build thread. Hopefully he'll see this and reply and tell us.

 

*EDIT* Sorry managed to skip over the line where you have already found the company that does the repairs. I think I need to go to specsavers!

Yes, they are the Caerbont instruments, whose co-located sister company, Speedy Cables, can apparently repair them, but there are three disadvantages to this:

The company's name is a bit of a misnomer in the sense that my and many others' experience with them is that they are anything but speedy.

Second is that I'm told that they charge upwards of £50 to repair each gauge, and third is the fact that I would still have delicate plastic casings.

[Chillidoggy]

They are speedy, but only with cables!

[Zulu10]

3 minutes ago, Chillidoggy said:

They are Caerbont gauges, and yes, Speedy Cables did the refurb on them, including new casings. Definitely cheaper than new replacements, but they did take a long time to do.

In my opinion, the cases probably fail due to over-enthusiastic tightening of the securing screws, and/or knocking them when they’re in situ. They really don’t need to be that tight, but if you change them for another type, the originality has gone.

Thanks for the confirmation.

I agree with the issue of originality of the front of the gauges, but am less concerned about the casing since it can't be seen with the gauges in situ. Hence my desire to reverse engineer the shape and then increase the thickness of the casings to add strength.

[Chillidoggy]

My oil pressure gauge fell out while  @Sparkywas driving.

[jonwat]

1 hour ago, Chillidoggy said:

My oil pressure gauge fell out while  @Sparkywas driving.

Same here, except I was driving. 😡

Decided the plastic body had broken because the clamps had been over tightened & easiest repair was to glue it back together then fix some sort of support to the dash in order to take the weight to stop it happening again.

Edited July 1, 2020 by jonwat

[Sparky]

11 hours ago, Chillidoggy said:

My oil pressure gauge fell out while  @Sparkywas driving.

You say that as if it was my fault.

[C8RKH]

It's always your fault! Just ask your wife for confirmation.

[Chillidoggy]

21 hours ago, Zulu10 said:

Thanks for the confirmation.

I agree with the issue of originality of the front of the gauges, but am less concerned about the casing since it can't be seen with the gauges in situ. Hence my desire to reverse engineer the shape and then increase the thickness of the casings to add strength.

 

My gauges had all new plastic casings fitted by Speedy Cables and have been good as gold for 5 years/15,000 miles now. If you fit them carefully enough and don't overtighten them, then they'll be fine. I can't help but think that what you're proposing is a lot of work!

[Zulu10]

30 minutes ago, Chillidoggy said:

 

My gauges had all new plastic casings fitted by Speedy Cables and have been good as gold for 5 years/15,000 miles now. If you fit them carefully enough and don't overtighten them, then they'll be fine. I can't help but think that what you're proposing is a lot of work!

You're right there's some work involved. I'm waiting on a quote for the scanning and reverse engineering into a CAD file.

Alternatively, I keep threatening to learn how to use a CAD package properly, so this might be the ideal opportunity to simply draw the casing shape from scratch.

There are many of the intricacies of the Caerbont casing that do not seem relevant to our gauges, so they could be omitted, whilst taking the opportunity to slightly thicken the plastic case.

Then of course I'd have the ideal excuse to buy a 3D printer... 😉

 

On reflection, I could also update the mounting to use a finely threaded external collar, rather than the metal bracket.

 

[Chillidoggy]

12 hours ago, Sparky said:

You say that as if it was my fault.

To be fair, you were driving ‘enthusiastically’.

[Sparky]

Lucky it wasn't Bibs.  You'd have lost anything not nailed down.

[Chillidoggy]

2 hours ago, Sparky said:

Lucky it wasn't Bibs.  You'd have lost anything not nailed down.

Richard’s strengthened gauge cases would be a prerequisite in that instance. Part number A910EB1B5 refers.

[Zulu10]

You were right: learning a new CAD package is v. hard work! However, I'm pleased with the result. Just need to talk to a 3D printing house in the morning... Have now found a print bureau in Portsmouth who have an on-line quoting system that suggests £10 or so (presumably plus VAT) per unit, plus a small set up fee.

 

[Zulu10]

Updated version with partially threaded mounting studs and fillets around internal right angle corners:

 

[petecov]

Nice design. Keep us posted.