Member postings for Luker

Hi Tim. I understand your reluctance to consider using home-made items, albeit a little odd in the context of this forum. Unfortunately I don’t share my free body diagrams, hand calcs or numerical checks simply because people aren’t generally interested in such things nor will they understand mesh dependency checks or sensitivity analysis, etc. An experienced design engineer would have noticed the lofted upright designed to distribute the stresses to the lower ring, as well as the curved geometry to drastically improve strength while using less material (improving castbility). This of course all falls apart if you don’t grasp the fundamentals of casting aluminium and you get fade, or gas pickup or casting inclusions due to poor riser and ingate design. Again an experienced foundry-man would notice the lack of casting defects typically evident in the region of the ingate.

The pad-bolt is brilliant and is used extensively in other applications on all my bikes. Specific to the Blackbird uprights; the clamped ‘ring’ is locked in place by a ring clip at the top and located to the bottom yoke by a small tab, so the required gripping force isn’t that great. Incidentally my pattern was symmetric with the LH and RH tabs machined flat respectively.

I’m a firm believer that anybody can do anything with a little reading and just giving it a go! The notion that ‘home made’ is not as good as ‘professional’ is (in my humble opinion) an absolute fallacy.

Thanks guys.

Dave; I'm very lucky where I stay, the roads are generally quiet and the trees line the roads so you drive in the shade. I did cut out most of the traffic bits in the video though.

Yep, I've also had to fix the loom. And the cam chain tensioner, which is a fantastic design, pity the manufacturer didn’t put much effort in keeping to tolerance. After re-machining the problem bits the tensioner has given me no issues. Its a good thing I can make things because parts are getting very expensive and more difficult to source.

I agree, I don't use the bike as the designers intended. I was considering getting a cruiser but my bike is apparently worth nothing; besides when I was walking round the bike shop looking at what’s available I was rather disappointed. One particular bike (completely out of my price range, and something I wouldn’t be seen driving out of pure embarrassment) had some of the worst welding I’ve ever seen on the exhausts. The welds were sensitized and there was clear over penetration. The Blackbirds welding still has the discoloration with no corrosion after all these years. I was not very popular when I pointed that out to the sales guy! Needless to say I decided to take my worthless bike and modify it to suit me…

Some interesting machining and casting I did recently for my bike. Thought it may be of interest...

Thanks Bezzer. Made my bike a dream to ride! I redesigned the risers completely. They moved back with less of an angle backwards, raised and the vertical angle is different aswell. These were cast from Mag wheels, and I didn't get any gas issues or inclusions. I didn't de-gas any of the castings done on this day. Cost me nothing to do, even the wheels were free from a friend that moved...

Sand additives and dusting was normal flour.

Hi Ken, yep otherwise they would be called 'don't know how to drive valve' instead of safety valves. Easier said than done but should be a matter of pride to try and drive without letting the safety's blow off. They should be designed to prevent damage to the boiler even with a good fire and blower on full, so in theory nothing should get damaged. I don't bother with keeping the cylinders hot in the station, on my scale I seldom get priming even after a good chat in the station.

Our rule is, in the station the loco needs to have the reverser in mid-gear to prevent mishaps if the regulator isn't shut properly.

The choice of stainless was actually based on thermal simulations of one of my boilers. Counter to popular belief, the lower thermal conductivity has benefits for the heat transfer and nucleate boiling on the tubes. Practically, if I compare two of my boilers with similar volume/heated surface area the stainless steel does outperform copper. It also stays much cleaner inside the boiler. I checked one of my stainless boilers that has been steaming for a little under 6 years and when I put the scope down the wet-leg there was no build-up. The copper boilers have scaled far more than my stainless boilers. Bear in mind that my boilers are relatively small, and if I were to ever make a large loco I would go for steel.

Pitch copper or oxidised copper is another animal entirely, but not that common nowadays. You'll pick it up quickly when you try to TIG weld it (will just make a porous weld).

Starch works as a degasser (for aluminium) or footpowder. If you have turbulence when pouring you will get gas pickup especially if you have too much superheat.

Cast these recently to make my bike a little more comfy.

The OP was for a TIG welded copper boiler, and this is to save the cost of silver soldering the joints. I’ve only built (TIG welded copper) one such boiler and it still steams just fine (10 years later). I agree with you questioning the use of copper instead of stainless. To digress a little, stainless steel TIG welded boilers work incredibly well. I’ve designed and built 4. Life cycle fatigue (and surface potential calculations for corrosion cracking) is normally catered for in the design phase and cannot be determined by NDT, but that is outside the scope of this thread. Boiler plate is technically more difficult to TIG weld than stainless (and normally not recommended), so we need to be specific with materials and welding procedures.

Of course if you weld with clothe hangers, and rusty wire you’ll get rubbish… I’m not sure why anybody would TIG weld copper with Phosphor bearing rods, this doesn’t make sense.

Engineers solve real world problems from first principles. Bureaucracy hamstrings that process by adding unnecessary constraints restricting solutions. I.e. How does a professionally checked sample add any more value than having a technically competent club boiler inspector check the sample, and then help and guide the model ‘boiler maker’?

There's lots of; could happen, might, what if (fear and more fear)... a little like what insurance companies and bureaucrats preach when they try to get you to do what they want you to do. Engineers do take responsibility by driving directly behind the boiler(s) they made; this position and the front of the boiler is arguably the most dangerous. ME shell design safety factors are orders of magnitude larger than large scale.

Don’t get me wrong, rules and guidelines are welcomed especially for the beginner. But honestly, professional weld sample tests for a small welded boiler. A couple of destructive weld samples tested for the boiler inspector at the club workshop should be ample.

At our club we emphasis good driving and boiler management practices; nearly all failures I’ve come across can be attributed to abuse while on steam. If the boiler passes the shell test and the safety valves are adequately designed and maintained then any problems are driver related.

My method... (the video was done quickly on my phone for a youngster)

I’m sorry Jelly but I don’t agree. ‘Rapid fatigue’ (low-cycle fatigue) failure is uncommon in welded copper (or copper in general for that matter) due to the ductility of the material and the heating/annealing during the welding process. When welds fail due to ‘cracking’ in copper it’s normally due to hot tears because of low melting point (elements) contaminants that never went into solution; or just poorly designed welds.

TIG welding isn’t very forgiving when it comes to visual inspection. Unlike some of the other welding processes it is very easy to pick up poor quality welds. In industry, 100% NDT is normally limited to dye pen and MPI, both of which won’t pick up root defects, and won’t pick up much more than a good set of eyes and some good light. UT and X-ray picks up root defects and sidewall fusion defects but this is practically limited to a percentage of the welds. Personally I have very little faith in these reports, they only good for the bureaucrats and lawyers. I’ve stopped a few components from going to site where all the NTD passed inspection scrutiny but visual inspection made me look a little deeper and low and behold there were welding defects that were very dangerous.

To Godley’s point (and I agree with him): In industry, as with hobby boilers, my go-to has always been the pressure test and the visual inspection of the welds. It’s not easy to gippo these two tests.

The sad fact is; with all the legislation/ bureaucracy and club boiler inspectors that are unwilling to up-skill you effectively limiting innovation and restricting the hobby to people with deep pockets. Where, in the past, the rest of the world was looking to the UK for innovative designs and manufacturing techniques with our models, now it seems like other countries are leading, especially with boilers. Maybe its time to take your hobby back from these bureaucrats!

Somebody asked me to explain the Touch and engage method described in the series so I very quickly did the following video. Apologies’ in advance for the poor production and lack of editing (just done with cell phone in hand!), but it does show the method (more or less )

I had the same problem. I contacted the helpdesk (via email) and they helped me out very quickly...

My humble view is: if you visit a club and they don’t have your specific branch of interest in ME then that’s a great opportunity to start a group within the club.

We have public running days on all our members or open days; that’s how we stay afloat. There’s enough room on the track for everyone and all members are encouraged to bring their loco’s (or anything of interest for that matter) for the public to have a look at and discuss with everyone present. The ‘odd’ little loco’s (that don’t necessary pull public) bring the foot-traffic that puts the bums on the paying rides. We also have an open table for members to show their builds which often ends up in discussions and appreciation from the public.

Personally I don’t like hauling public, but I’m there most days with my little loco’s…

It really does boil down to how you look at things!

Pat you need to be careful to mention this is case specific. With phenolics or resin binders the mould is considered rigid which contains the expansion phase with cast iron, then with most of our size castings risers aren't needed and the ingates aren't that important. With moulds that 'give a little' like green sand you need to be careful with the ingates and risers because the sand doesn't contain the expansion, and there is seldom enough in the sprue to feed. Besides if you start casting components with a larger casting modulus (large volume to surface area ratio) you might need to revisit riser design...

As a comparison; I typically cast around +20Kg per casting session that’s 5 pours (cast iron), and I plan my moulds to empty the crucible with each pour. It takes around 1½ hours (controlled heat-up) from a cold furnace to the first pour with cast iron and after each charge it takes 40-50min to melt from an empty but still hot crucible. I burn between 15-20l (4,2L/h max, or 1,1USGal/h) waste oil per session but a large portion of that is wasted during start-up. Recently I've averaged at the lower part of that range but this is the total log book average. The furnace will smoke a little for the first 10-15min and after 30min there is no smoke coming from the furnace. When I cast Aluminium and the bronzes I have to run my furnace at a lower efficiency otherwise I can’t keep up with the furnace and I get fuming in the crucible and burn-on in the moulds.

Many, many, many things!

I took up casting out of necessity, because I couldn't afford castings. I designed and built my furnace from first principles, so that was up and running relatively quickly. Other than the lid mechanism the furnace hasn’t changed much over the years. I’ve only relined once (a few years back). When I started casting I visited a foundry and got some advice and phenolics from the foundry manager. My very first attempt at casting was a failure and I quickly realised the advice was rubbish but the phenolics worked well.

I read a few engineering books on casting and modified the maths and assumptions for the methoding of my smaller moulds. The next time I cast was a success and other than the odd short pour or burnon I don’t have many failures. The initial calculations were all hand calcs but I later wrote an algorithm to calculate the ingate, risers etc.

Incredibly I even managed to cast the firebox hole for the boiler in copper (one of my first pours), a little luck involved here. That boiler is still going strong.

My first cast iron casting was the large wheels for my Stirling 71/4g. Phenolics were not available and I decided to go for green sand, which makes more practical sense if you casting larger moulds more often. I couldn’t include risers and the sprue needed to be smaller due to the size of my cruicible. This was difficult to cast and I had to pull a few tricks to prevent draw. Ironically a rigid mould using phenolics would have worked fine because the expansion phase feeds the mould without the need for a riser.

Cylinders for the Ballaarat:

Cast iron straps and cast iron eccentrics for the Wahya, these worked incredibly well:

And then there's all the special handles for the various builds: These were tricky because they are double sided with a split pattern:

Edited By Luker on 04/07/2022 20:17:43

Pat you may like these, some slightly more technical castings:

The compensating lever (as cast) on the Wahya, the thickness is 4mm with the ears and middle opened to a 2.5mm wall thickness for the upright levers to go through. Its a ductile iron (mixed from pig iron to get the chemistry correct). This lever is on the suspension and sees a lot of vibration from the track:

The bogie wheels cast for chill on the running surface, by changing the FeSi and (outer) sand composition. The axel boss needed to be softer for a press fit. The outer surface was machined with a tip tool and was much harder than the rest of the casting.

I cast a lot of smaller components for my locos. These get polished in a DIY tumbler.

Here's an interesting component with a zero deg draft on the outside and a 5 deg rammed green sand core all the way to the lip. This was rammed normally (with nails) to keep the core in place when removing the pattern.

Bogie pedistals with a rather thin wall thickness (to scale) that has managed to survive our rough track