Quarry Slab Trucks

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workwright
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Quarry Slab Trucks

Post by workwright » Mon Apr 17, 2017 11:36 pm

Hi, I have just purchased a laser cutter after a year of humming and harahing. It is an Ebay, Chinese 50W machine. Getting it up and running was easier that I had expected having spent the previous year reading mostly rather worrying reports about the machine. However so far nothing has gone too wrong. To learnto use the machine I decided to make a model of a quarry slab truck. There is a very nice drawing and a photo or two in the Talyllyn Railway by J C Boyd. For such a common wagon in the Welsh slate quarries there are very few drawings. Once measured up I thought I would make it as a kit in acrylic sheet(Perspex). Why a kit? Well they are common and I thought 10 or so in various states of decay would look interesting.
Perspex is a lovely material to work with since the laser cuts it very cleanly, it is easy to bond with Plastic Weld or similar is very strong and is oil tolerant and given the running these models will see the material works well as a bearing for a steel axle.
Image
The frame is made of two parts laminated, the draw bar is preformed and retained in a slot by the end cross beams. The axleboxes are laminations assembled on the axle and all the parts are lightle engraved to aid assembly.
Here is a pristine slab truck just built and painted.
[img
slab2.jpg
][/img]
The last photo shows a quarry Hunslet of mine with the first slab truck made- just to get me in the mood to knock up some more which will be distressed and be painted up to like like really old wood. I will need a trip to Wales to find some thick slate to load them with.
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Re: Quarry Slab Trucks

Post by pippindoo » Tue Apr 18, 2017 12:25 pm

Looking great for a first model! I can see you're​ going to need more sidings though...... :thumbup:

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Re: Quarry Slab Trucks

Post by GTB » Wed Apr 19, 2017 2:39 pm

workwright wrote:
Mon Apr 17, 2017 11:36 pm
Hi, I have just purchased a laser cutter after a year of humming and harahing. It is an Ebay, Chinese 50W machine.
I looked at desktop laser engravers a few years ago when I was still working in HO, as they do a good job cutting polystyrene sheet. Never got around to doing anything about it though...... :roll: What sort of laser tube life do they offer these days?

The acrylic parts have come up nicely, but I'm more interested in the dummy square nuts and washers you've used for detailing. How did you do those?

Regards,
Graeme

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Re: Quarry Slab Trucks

Post by Busted Bricks » Wed Apr 19, 2017 3:17 pm

Don't run the machine at full power. Those tubes are not really 50W but are often being over driven for higher power. This reduces their lifespan. It should not be run at more than 18mA. This video is worth watching:
https://www.youtube.com/watch?v=KQDCy-mPNqA

If you machine does not have an ammeter there are videos on Youtube on how to add one.

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Re: Quarry Slab Trucks

Post by workwright » Wed Apr 19, 2017 8:59 pm

Hi, GTB the square headed bolts are castings I made myself a long time ago in whitemetal, however a nearly identical product is cheaply available from Cambrian Models in the form of two plastic sprues of square and hex headed bolts and washer plates in 3-4 sizes. I recall that there about 50 injection plastic items on each sprue.
The question of lifetime of water cooled CO2 laser tubes is an interesting one. Busted Bricks makes an excellent point which is much debated on the web. Most early tube failures are due to users using the software power settings. When you first fire up the machine and check it out it takes forwarning not to pulse the tube at the setting on the screen. If it is set at 100%, as mine was and I had pulsed it, even a few times, to check the optical alignmets I do not think the tube would have lasted more than an hour or two. Luckily I was forwarned and I had made an ammeter and temperature monitor before I used the machine. Again Busted Bricks is correct. The maximum current on the return side of the laser rated at 50 W is 16-18MA. I assume my 50W tube is in fact a 40W tube or possibly 45W (it is only 850mm long) so my maximum safe current is 16mA which is achieved at a software power setting of 32%. A setting that at 5mm/s will clean cut 6mm perspex and at 20mm/s 4mm ply. Also using a block of perspex maximum penetration of the beam 14mm was achieved at 32% power. Lifetime of the tubes is probably 1000h but there is a confusion in this since the tube degrades from its date of manufacture. Hence some makes say the tube life is 10,000 or even 20,000h! There seems no standard system. In conclusion fit an ammeter on the RETURN side of the laser NEVER on the fed(+) side. Why? the (+) end carries 15kV working and up to 25kV firing at a signicant amperage. One mistake at this end will certainly be your last. Never poke arround these voltages. The machine must be unplugged ,left overnight to allow any residual charge in capacitors to dissipate. Use a wandering earth wire to touch wire ends and components before your fingers or hand go near.(just to put this in context I have a large rotary converter, it developed a fault. I unplugged it overnight. Next day I slipped with a screwdriver and it passed over the top of a capacitor. reuult a flash and ban and the end of 3/16 screwdriver was vapourised). Remember also that some Chinese machines are not that well made so always assume the worst when fault finding.
Image
THis shows the ammeter and coolant water temperature monitor unit I made. To find out more about these machines enter 50W chinese laser cutter into You Tube and look for videos by"sabar" Russ, the guy that made these 100+ videos has done the laser using community a real service. He is a fount of knowledge and advice . By the time you have watched a few videos you will understand the machine, how to set it up, how to get good results and how to access an English manual (not the Chinglish one the machine comes with) Also you should try to join (it is by invitation) RDWorks-lab Forum.
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Re: Quarry Slab Trucks

Post by SpudUk » Thu Apr 20, 2017 7:58 am

Wildly off topic but what a beautiful Hunslet - who is the maker?
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Re: Quarry Slab Trucks

Post by Busted Bricks » Thu Apr 20, 2017 10:39 am

Nice to see you did your research before taking the laser into use. These are not bad machines if you know what you are doing. Used correctly, standard tubes will last a long time. I have a 80W RECI that I run at near peak output most of the time and it is coming up to 2000 hours now. I do production runs where speed is of the essence . I've just bought another laser with a 110W tube so I can cut faster. On this one the manufacturer actually added a label with max safe operating current next to the ammeter.

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Re: Quarry Slab Trucks

Post by workwright » Thu Apr 20, 2017 8:07 pm

Hi, Spud uk, the Hunslet was made by me. It was made in 1992 and was one of a batch of 8 I built. They were rather an error. Each (except this one) were near exact models of a quarry Hunslet as it was in a specific year. They all have full inside the correct frame profile, Rivets in the place they should for the given the prototype,full Stephenson's valve gear and consequently had gas tanks that were on the small size only having about 15mins of gas. They took a long time to built and even longer to get to run well, each was very much handbuilt and were in a business sense a disaster. The one in the picture is a quarry tank that never was. I do not think there ever was one with the attractive scalloped cab and a dome on the tank. It was my reward to myself for building them. My current Hunslets do at least use all the lost wax castings I made, so after a long wait the investment is starting to pay off!
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Re: Quarry Slab Trucks

Post by GTB » Fri Apr 21, 2017 4:02 am

workwright wrote:
Wed Apr 19, 2017 8:59 pm
Hi, GTB the square headed bolts are castings I made myself a long time ago in whitemetal,
Ta. I used to cast my own parts in type metal way back and I've still got the gear, but haven't used it for a long time. I've got a cache of NBW castings from Ozark Miniatures in the US, but he doesn't do square nut castings. Might have to make a pattern and break out the Silastic again.
workwright wrote:
Wed Apr 19, 2017 8:59 pm
The question of lifetime of water cooled CO2 laser tubes is an interesting one.
You and Michael are right, a laser tube won't react well to being overdriven. My understanding is the tube life of a sealed tube laser, if used within it's limits, is about the same whether it is being used, or just sitting on a shelf.

Back in the late '70s I had a high power CO2 laser cutter in the test lab. The mechanical bits were well made and the electrics were reasonable, but the laser tube design was a nightmare and probably contributed to me going prematurely grey. It became too unreliable for the purpose it was purchased for, but I did cut a few live steam loco frames on it and it was great for cutting acrylic. All G code programming back then though.........

Most industrial machines scaled down for the consumer market are accidents looking for a place to happen. The desktop lasers I looked at didn't have much in the way of interlocking to stop a user getting into the HV, or the laser beam for that matter. There's no IQ test required before buying machinery....... :roll:

Regards,
Graeme

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Re: Quarry Slab Trucks

Post by workwright » Wed Apr 26, 2017 4:44 pm

Hi, I spoke too soon about the laser. Last Friday the laser power supply went bang! I mean Bang! I have started a so far hopeless battle with the e-bay seller to acknowledge that it was sold with a 3 year warranty. As it seems worthless it could have been a 25 year one. I think I will have to try Pay pal next to see if they are any better at protecting a buyers rights. The trouble is that the laser is now so useful that I have to get it working again. I have decided to but a new power pack. Those that know tell me that this is the best way forward, then try to repair the old one since the wise Chinese laser cutter has a spare of everything to hand.
I am starting to research a coach built by Kerr Stuart for the Gwalior Light Railway hopefully this will mature into a real kit. This will be a multilayer kit in MDF with etched brass for some chassis parts and details, the bogies however are not a problem in that Swift Sixteen sells the correct type.
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Re: Quarry Slab Trucks

Post by Big Jim » Wed Apr 26, 2017 9:09 pm

Sorry to hear about the exploding unit. Paypal may be the best way to reclaim your money. Let us know how you get on with the refund it may prove handy if anyone has problems.
If at first you don't succeed, use a bigger hammer!

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Re: Quarry Slab Trucks

Post by pskipper » Thu Apr 27, 2017 8:24 pm

Hope you get the warranty sorted. Paypal does sound like the best way to go.

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Re: Quarry Slab Trucks

Post by Busted Bricks » Thu Apr 27, 2017 9:36 pm

They do indeed go bang when they go. I had one go. I had bought direct from a manufacturer so they replaced it under warranty.

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Re: Quarry Slab Trucks

Post by haleycuk » Fri Apr 28, 2017 12:03 am

tight from 3-quarter.jpg
Also off topic, but is this another one of the batch or a later one (dated MD Wright 1995 underneath). Lovely model in any event.

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Re: Quarry Slab Trucks

Post by workwright » Thu Jun 22, 2017 11:40 pm

Hi, that is a nice Hunslet. I do not remember the dome on the tank. I was rather careless about what I made in the past. I did not systematically photograph all the engines I made. Lovely to see an old friend again thanks for posting the picture.
Laser cutter- working with a new power supply. I got nowhere with e-bay or pay-pal. pay-pal was very annoying in spite of giving them the full claim history they came back after a month and said they had cancelled my complaint because I had failed to give them any material to support the claim??????. A guy on another forum in the US with a similar machine and claim also had the same thing happen. It is now very much buyer beware using e-bay/pay-pal.
I was determined to try to fix the broken power supply. With the help of a couple of guys who I first found on the web, one in Holland and his pal in the US after three attempts the power supply is again working for the cost of £5=60 in components. The great plus is that the guys got me to work out how the circuit worked, taught me how to test the components so the breakdown ended well since now I feel I could have a go at fixing another power supply. Since posting last the laser has cutout in card 1) all the parts for a model of a station building (Oscale) 2) 90 large palm fronds to built 3 very detailed 60 foot palm tress (O scale) and lastly 3) 600+ roman tiles to cap an adobe wall (O scale) (anyone interested can view on http://www.rmweb.co.uk/community/index. ... 50w-laser/ last post on page. All these projects would have been impossible without the laser.
I am going to see if I can turn a scratch built Kerr Stuart Guards van I built some time ago into a 16mm scale kit. I will post how I get on here. regards, workwright.
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