Here is a list of all the postings Luker has made in our forums. Click on a thread name to jump to the thread.
Thread: Loco Cylinder Casting Pattern Advice |
20/04/2021 16:09:26 |
Picture worth 1000 words... |
20/04/2021 15:40:29 |
HI Buffer, you need both cores if you don't want large risers to prevent draw. You can use a staggered split line. When ramming patterns with a non-uniform split line you place a little casting sand on the moulding board, dust then push the pattern into the sand and ram normally. Then with the other side of the pattern you remove the bottom sand and continue as normal (normally it just drops off when you lift the box). You going to need casting radii to prevent corner draw on those webs as well as a decent draft to get proper (tight) ramming in those pockets, otherwise you are going to get burn-on. Hope this helped! |
Thread: Design of boilers |
20/04/2021 09:17:14 |
Posted by Nick Clarke 3 on 04/03/2021 09:43:55:
Posted by Luker on 04/03/2021 09:34:42:
I am not a fan of any requirements for professional or welder certification for the smaller boilers. In the UK a non-coded welder needs to submit recent weld samples to professional inspection to comply with the current boiler code in addition to the inspection by a club inspector. This applies to all welded boilers and the material (welded steel or TIG welded copper) is not specified. See paragraph 6.2 here **LINK** Hi Nick, I’ve finally had a gap at work and gone through the UK 2018 boiler test code (thanks again for the link). I found it a decent code to read. I’ve read far worse! Interesting stainless boilers isn’t specifically disallowed; it just can’t be tested using this code due to “specific” requirements. This makes sense if boiler inspectors aren’t trained with certain materials and current manufacturing practices. The code allows for a 3rd party boiler inspector to certify a published design of such a boiler provided he understands working with stainless (and is commercially certified). Boilers according to the code can be welded by “non-coded” welders but test samples just need to be commercially tested (as you pointed out), here I’m not sure if this will show any more than the standard v-sample vice bend test. Incidentally I think the section with the minimum sight glass point above the crown is a little dodgy; there should be a specified min value typically 10% top of nut. At our club the boiler construction and testing follows and exceeds the requirements of this code, other than the use of modern materials and construction techniques. With this comes the necessary calculations and testing to make sure it is safe. As modern materials and techniques become more common place hopefully clubs will be more comfortable with newer techniques. |
Thread: Wahya construction series |
19/04/2021 15:20:29 |
Some pictures and schematics of the tender, described in the last article... The breaks were interesting for me. |
17/04/2021 13:15:15 |
Hi Everyone, A few more pictures of the Wahya cab... The steam valve handles are some of the smallest castings I've done (4 gram). The pointer in the gauge was made using a cellphone charger (electro-stripping technique). |
Thread: Pattern making using 3D printing |
12/04/2021 18:04:41 |
Posted by Brian H on 12/04/2021 17:54:37:
VERY interesting article. Are there any 3D printing materials that can be used in the same way as 'lost wax' ? That is without the need for runners. I realise that this would destroy the pattern but it would be easy enough to print another. Brian Yep, that's in part 2 |
12/04/2021 17:28:32 |
Thanks Ady, Neil. I do actually use Cura, but I personally prefer to scale in the modelling package, with the pattern a linked part so it gets updated if the model is changed. The biggest problem with scaling in Cura is with items with a large hole (like eccentric straps or any part with a cavity in the middle that will be rammed); when scaling, the hole gets bigger but in the mould the metal shrinks away from the sand, again making the hole bigger. So you actually need to scale the part then resize the hole smaller to remove the scaling you’ve just added, minus metal shrinkage and any machining allowance. Sadly the story in my article of the tips I order being liberated is actually a true story. I agree though if you can get the nozzles rather buy them. Incidentally the brass nozzle I made has lasted 2Kg and is still going strong, I’m not sure how long they should last? The picture is of some castings from 3D printed patterns (cast iron) but the cavities required the resizing (smaller)… |
11/04/2021 13:04:45 |
I was inspired by Jason’s thread and pictures of his Thompstone engine, so I took a few pictures for the “Pattern making using 3D printing” article. It morphed into a video, which I’m going to pay dearly for next time my beautiful wife wants to make a rotisserie chicken. The video shows the 3D printed patterns and the (green sand) cast components. All these components are used in my various live steam locomotives, with all the patterns printed using ABS and cast in my back yard using a home-made waste oil furnace. The materials shown in the video include two different grades of cast iron, brass and alumina bronze, with most of the alloys mixed from scrap or base metals. The methods and techniques for this type of pattern making and casting is explained in the articles as well as methods to use these techniques for investment casting and flexible mouldings for those of us that enjoy restoring vintage bikes and need to make badges. |
Thread: Thompstone Engine |
07/04/2021 07:58:15 |
Hi Jason, I read part one yesterday, enjoyed the write-up and I am looking forward to the rest of the series! That is one fine looking engine |
Thread: Loco wheel profile chatter |
03/04/2021 09:54:03 |
Hi Nigel, all makes sense, but if you’ve machined over 50 wheels it’s more of a chore than fun. The beautiful thing about this hobby is you can never be bored, currently my interest is in developing an alternative alloy for steam cylinders as tin is becoming exorbitantly expensive; cast the first cylinders a few weeks ago. The little ‘skinny’ mandrel handles a 1.5mm roughing cut without complaining which is not bad considering I mix my cast iron to be harder on the outer profile for my non-tired wheels; this is of course with chromite sand in this area. The wheels I cast in this fashion actually outperform the tired ones. I started restoring bikes when I was at school, I don’t recall having any problems clocking the drums and skimming. I do however recall battling with rebuilding and truing up the wheels. If you interested in vintages I’ve uploaded pics of my 58 and 25. I had to make the brake shoes for the 25 as they were missing. This morning I did a few experiments on a spare wheel, and I found a few ways to get rid of the chatter. Buffer’s method worked also, thanks for that. I think this little exercise will make a nice write-up, thanks to everyone that pitched in and steered me in the right direction. PS: Buffer can I mention your method? If so can you PM me your name for reference. |
02/04/2021 20:21:12 |
Posted by Weary on 02/04/2021 19:36:45:
Hello Luker, LBSC's mandrel for turning locomotive wheels was fitted as follows: "Chuck an odd casting or disc of metal a little smaller than the back of the wheel ..... recessing at the middle for about 1/32 in depth and 1 in. or so diameter" (quote from 'Virginia' notes, but similar wording appears for other builds) and then fitted with a mandrel which was subsequently turned to appropriate diameter. Thus the mandrel was principally for centering the wheel which was fully supported by the 'odd casting' or 'disc of metal' held in the chuck. The nut on the end of the mandrel was used to pull the wheel back into firm contact with the ad-hoc faceplate. Regards, Phil Hi Phil, I stand corrected. I just checked my Martin Evans book and he followed a similar approach. Looks like I found a novel way of doing things, and as a plus my wheel flanges have additional grip for those corners |
02/04/2021 20:14:09 |
Posted by Michael Gilligan on 02/04/2021 18:58:10:
If the chatter pattern is identical on both spoked and solid wheels, and on different materials, then of course I’m happy to believe that the tool [or its mount] is to blame. MichaelG. Top picture is of a spoked, tired wheel 150mm dia. Bottom picture is of a solid 65mm wheel. I think the pattern is very similar considering the large difference in parameters, but I'm not an expert in these things! |
02/04/2021 18:00:36 |
Posted by SillyOldDuffer on 02/04/2021 17:30:24:
Can you publish a picture of the tool in the lathe please Luker? Looks like a vibration problem, and although Michael's cymbal is a credible suspect, tool shape and overhang may be making it worse. Vibration is a funny animal, not always obvious what the cause or mode is. That it vibrates at a particular point must be a clue, but I can't visualise what the cutter looks like. Rubbing rather than cutting maybe, and that can be due to bluntness, incorrect rake and/or relief. The cutter may be scraping like a horse-hair bow across a violin string simply because the geometry isn't quite right. I'm guessing! Dave
The lathe has another setup in at the moment, but here's the tool. I try to keep the overhang as small as possible, not more than tool thickness, in this case 12mm. Rake and relief is ground for CI but I machine the EN8 tires with this tool as well. It gets ground between wheels sets, that's why it looks freshly ground. I've just finished a wheel set. Your descriptive words for vibration are brilliant! Please can I use paraphrase and recycle? |
02/04/2021 17:39:49 |
Hi Phil, Yep I’m going to give the faceplate a bash again; my Stirling single wheels were machined like that, but they were very large wheels with two taper slide setups so can’t really compare. I swopped over to the mandrel method with the last two loco’s I made because they had solid wheels, so a drive pin was not possible unless I deviated from the original. One positive about the mandrel method is that’s its very quick. The last loco had 12 smaller wheels that were completed in a Sat morning. I was hoping for a “trick” that I had missed, but I will definitely machine a wheel on a faceplate to compare. |
Thread: Noel's file cleaner |
02/04/2021 17:24:11 |
I made Noel's file cleaner, recently described in ME. Works like a charm. Thanks for the tip Noel... |
Thread: Loco wheel profile chatter |
02/04/2021 16:50:28 |
Hi Guys, Thanks for the feedback; you’ve given me a few things to think about. Michael, I liked the article, thanks for the link. I can’t say I know much about vibration; it has been a while since I’ve done a modal analysis, but I personally think the problem lies on the tool side. Sorry I should have elaborated a little more in the initial post. I have had the same result with spoke’d and solid wheels, with different materials so this should have shifted the modal point, but the intervals between the chatter ‘marks’ were identical. This makes me think the problem is on the tool side. Thanks Duncan, next time I’ll have a look at a wheel turning setup like you’ve described. How many wheels have you machined using this method? The greats like LBSC and Martin Evans used to machine their wheels using mandrels? |
02/04/2021 11:14:57 |
Hi everyone, I have a question for the loco making guru’s. Whenever I machine the profile of the wheel I get chatter on the inner flange. Basically I machine a “square form” on all the wheels using a mandrel, then with a carbide (ground) tip, silver soldered to a dedicated holder I plunge to form the flange and finish off the taper using the taper slide. I machine in this fashion so that I can zero the lathe and cut all the wheels identically, and it’s much faster. The chatter only happens in the second I move from the top slide to the taper slide. I get the same with EN8 tires or from a profile machined directly to a casting. Is there a trick I’m missing? |
Thread: FOUNDRYWORK |
18/03/2021 18:59:30 |
Spot on Noel, can’t add anything to that! You should share the YouTube link of you casting; I found it very interesting. I picked up one or two tricks from that video… Believe it or not I had a gap day yesterday and did a few castings. Aluminium for the chimney (to bring the CG closer to where I want it for the new loco, but this is painted), copper cap, and AlBr for the bearing bits and cylinders. The safety valve cover and steam dome is normal brass. These castings were given a light sand blast and the ingates have been cut off, I still need to clean the flashes off and beautify. |
Thread: source of bronze |
11/03/2021 14:07:43 |
Posted by noel shelley on 11/03/2021 13:36:09:
Hi Luke, I wondered if you would stay silent or join the fun ! Knowing of the issues in your neck of the woods was my reason for stating "in the UK"! The preoccupation with precise alloys and industrial standards is hardly relavent in our scales, so long as it is safe and works does it matter ? If it has 2%Zn, 0.3%Ni, 3% Pb, 8% Sn If any of the whole numbers vary by 1 or2 % does it make any significant difference ? If you make your own alloys you only know what you started with not what you have in the end, most notebly a loss of Zn. For bronzes, which is where this started, it can be bought in ingot form, 7Kg and £9 per Kg =£56 +vat and carriage! Tin £30/Kg Or buy off cuts and smelt. Best wishes Noel. Yep I agree. Nice thing about having limited recourses is it forces innovation. Fuming was a problem in my furnace; I originally designed it for melting cast iron. My capping mix pretty much solved that (If I remember correctly I did send you the recipe, did you give it a bash?). I know you’ve mentioned to me before to use a pyrometer but the thermocouple and sleeve is a little expensive here. I have found that after my first pour I’m normally spot on with the pouring temperature based on time and the metal dipping bar. Most alloys are specified as a range, I mix based on mid-range with the Zn, and Si at the upper end with the tests I’ve done very close to “spec”. You guys are lucky with the ingot price, that’s what the scrap merchants here want for brass! |
11/03/2021 13:05:06 |
Hi Noel, nice to hear from a fellow foundry man on this topic. In my nick of the woods getting anything is tricky, even buying from a scrap merchant is a nightmare. If they do want to sell you scrap they sell it at LME prices, but typically they just refuse. The coal/coke etc. trick to cover the melt works really well but if you mixing and melting alloys and fines you need a little more to strip the oxides off the surface. I have cast numerous boiler components and have never had any issues, mostly from mixed alloys to get the specific grade I was looking for. If you interested here’s a little video a good friend of mine put together some time back. That little loco is still giving me loads of fun on our track, had a good days steaming this past weekend. |
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