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Member postings for Roger B

Here is a list of all the postings Roger B has made in our forums. Click on a thread name to jump to the thread.

Thread: Are Model Engineering Exhibitions The Same
15/08/2018 09:57:33

Things have obviously moved on, Duffel bags used to be the bag of choice for railway enthusiasts to complement the anorak.

Thread: DC motors
19/07/2018 12:16:16

If the loads can be well balanced series connection could work. If you go to worst case and have one motor jammed and the other free the free motor will get most of the 48V.

Series / parallel switching of motors was (is?) used in full sized traction but these motors had series field windings. The permanent magnet motors you have are closer to shunt field motors.

Best regards


Thread: Powered Bogies
10/07/2018 10:51:01

Long ago we built a 10 1/4" garden railway using cut down 2' gauge skip wagon wheel sets. This was powered by a Lucas C40 dynamo with the field rewound to operate as a series motor. Drive was by a V belt to a countershaft and chains to the wheels. The line was fairly level. With a driver and four passengers consumption was 10A at 24V (240W) Starting current was around 25A with a simple 2 step resistance controller.

battery electric railway.jpg

Thread: accuracy of silver steel
03/07/2018 10:58:06

I had a length of 'Lobate' 2mm silver steel a couple of years ago. I'm not sure of the supplier, possibly RC in Luxembourg.

This, after lapping to 1.97mm, would not enter a lapped hole that a 1.98mm pin gauge passed through. When I rolled a length on the surface plate with a ground V block the irregularity was audible. The pin gauge was quiet.

Thread: Hot Bulb and Glow Plug Difference
26/04/2018 10:54:23

John, to add pictures you first have to put them in an album via the icon on the green bar at the top of the page. You can then insert them in a post using the camera icon at the top of the posting box.

What I know of the Bolinder engines comes from the old engine website of which I am sure that you are aware. They also show an interesting load control system used on the Gardener hot bulb engine where the injector spray was asymetrical and the injector was rotated.


I would imagine that you would need an understanding of Swedish to get deep into the Bolinder history.

My interest is more in full diesels as I am currently building a 20cc horizontal 2 stroke diesel loosely based on the Field Marshall engine.

20cc diesel.jpg

It has run as a spark ignition engine with a carburettor and low compression cylinder head so I know that the porting and crankcase compression are ok. The fuel injection system works as manifold injection on another petrol engine. I am now trying to get the whole system working together but so far having only achieved blue smoke from the exhaust

Best regards


25/04/2018 14:57:22


The Lanz Bulldog was able to run on a wide range of fuels, some of which required different cylinder heads, water injection or fuel preheaters. This list gives some of the variations and is it is described as for a 45 HP Bulldog I would have to assume it was a 10 litre engine. This would give a range of compression ratios from about 6-1 to over 10-1. The book suggests the normal compression ratios were between 5-1 and 6.5-1.

lanz fuel.jpg

Injection timing is also a little difficult to define. The injection pumps were driven by eccentrics and in the case of the early engines the stroke of the pump was adjusted by a moving wedge which would alter the timing. The later engines moved the axis of the eccentric which would have a similar effect. Kurt Häfner states the timing as 120° to 135° before TDC.

lanz starter.jpg

The early tractors had an electrically assisted start system using an electric glowplug and a separate fuel pump and injector for what was described as ‘light oil’. The engine was still turned over by hand using the steering wheel. As you say the later tractors, especially the road haulage ones (Eil Bulldogs) used petrol in the second injection system and a sparking plug and trembler coil together with an electric starter motor. In both case when warm the engine was switched back to heavy oil. The units with an electric starter had a rev counter with a red area below 0 to warn you that the engine had started running in the wrong direction. It was assumed that if you had hand started the engine you should know this anyway.

Best regards


24/04/2018 11:41:21


I checked when I got home last night and found I had quoted the wrong book. The fuel system is in “Lanz von 1859 bis 1929” the previous volume by the same author.

The opposite adjustment of the injectors for the Lanz and Bolinder engines is due to the different layouts.

The Lanz injects across the hot bulb into a well. When idling the fuel jet is narrowed so it just goes into the well where it is vaporised and ignited. This small well will stay hot enough to maintain ignition. Under load the fuel jet is widened so that the fuel hits a wider area of the hot bulb giving a larger area for heat loss. The book notes that if the driver did not widen the jet when running under load the engine would suffer from pre-ignition and loss of power. If the jet was not then narrowed when the load was removed the bulb would cool and the engine would stop. A few minutes at the “wrong” setting was not a problem.

lanz injector.jpg

lanz cylinder heads.jpg

As Stuart Bridger notes the Bolinder injected through the hot bulb into the cylinder so in this case widening the jet will cause it to impinge on the hot bulb heating it up for slow running. Narrowing the jet allows it into the (water cooled) cylinder when under load.


Best regards


23/04/2018 12:58:38


My current interest is in full diesels but some of my future plans involve hot bulb/hot tube. I have collected some information that may be of interest:

Alyn Foundry produced a working version.


They are no longer trading but the original owner is active on Model Engine Maker as am I.

Some Italians have been making working models of Lanz Bulldogs and there variants such as Landini.



I also have a copy of the German book:

Lanz. Kühler-Bulldogs von 1928-1942. By Kurt Häfner.

This contains a lot of technical details including the different cylinder head designs used for different fuels and the injection system including the petrol injection, spark ignition starting system.

I hope that some of this may be of interest.

Best regards


Thread: air cooling options
10/04/2018 13:04:04

I think there are two main reasons why the cooling fins are machined in place on model IC engines:

The first is trying to achieve a prototypical look if the model is based on a full size engine.

The second is mechanical considerations. The cylinder barrels are usually fixed to the crankcase and the cylinder head is then fixed to the cylinder barrel. The barrel needs to be able to take these loads so the depths of the fins are often adjusted in these areas to allow for the fixings. There are some designs where the head fixing bolts go down into the crankcase which would remove this constraint.

Thread: 1831
09/04/2018 07:18:52

Excellent yes There are many examples of the petrol engine around but very few locomotives.

Thread: Wind turbines get bigger and bigger
06/04/2018 16:09:40

Dave, I agree that the American Thinker has it's own agenda, but they will post pictures of abandoned wind turbines which the pro renewables sites tend not to due to their own agendas. You have to gather information wherever possible and try to determine it's validity.

Best regards


06/04/2018 08:28:53


I believe the wind turbines were abandoned when the subsidies stopped as it was no longer economical to maintain them. When the gearboxes failed there was no sense in replacing them. You made more money building new turbines and starting with another 20 years of subsidy. I expect the same will happen in other places as the turbines start to age.

I don’t think the German model is a good example. The have decided on political not technical grounds to shut down their nuclear power plants, they have invested Billions in wind power, have one of the highest electricity costs in the world and have failed to reduce their CO2 emissions which was the reason behind the Energiewende.

Most of the nuclear decommissioning work in the UK is linked to military usage. The first two piles at Sellafield/Windscale were solely for the production of military grade plutonium. Britain’s fleet of Magnox reactors were designed with a low energy density and online refuelling again to allow the production of weapons grade plutonium. The low energy density means that the cores are much larger and hence there is more active material to deal with at decommissioning. The low burn up required for the plutonium manufacture results in significantly more material being reprocessed and hence more waste. 5% burn up will produce ten times more waste than 50% burn up. Most of the costs of decommissioning are directly related to the military requirement for plutonium during the cold war period and as ever with the military the taxpayer pays for them to make the mess and then pays to clear it up afterwards.

No I don’t work in the nuclear industry but I do like to find the facts not follow the dogma.

Best regards


05/04/2018 12:20:08

This facility was shut down in 2016, I haven't found any explanation, and a methane production facility is apparently being built on the site. Link (in German).


05/04/2018 08:44:37

I think that one of the major barriers to developing thorium technology is that currently uranium is too cheap and abundant. It is possible to burn thorium in current generation reactors but how you breed it to fissile U233 has some challenges. Ideally you want to avoid external reprocessing so a lot of shuffling of fuel rods would be required.

The other options of the various next generation reactors have some other challenges. The travelling wave system is quite interesting but is currently being developed for the in situ breeding of U238 to Pu239 which is subsequently burnt rather than Th232 to U233.

The molten salt systems have significant materials challenges although Terrestrial Energy is hopping to apply for a construction permit for a prototype by the end of next year.

04/04/2018 12:13:05

On a lighter note the German Police stopped this 'convoy'. I think he will find one of these new blades harder to transport wink


04/04/2018 08:57:12


Which experts are which? There are some who actually know what they are talking about and some scaremongers who just make things up.

George Monbiot who is deep Green Left discovered for himself that the ‘luminaries’ of the anti-nuclear movement are just making most of it up and can offer no evidence for their claims. These are his experiences with Chris Busby and Helen Caldicott:


Busby started out with good intentions investigating the childhood leukaemia cluster at Windscale/Sellafield but when he found the radiation levels were not sufficient to be the cause he left the scientific way and started making things up to back up his beliefs. If Sellafield/radiation was the cause the leukaemia cluster would still be there, it isn’t.

Others are now starting to take on this scaremongering, one example is Mothers for Nuclear


They also realised that most of the anti –nuclear information was rubbish and have started trying to add some reality.

Best regards


04/04/2018 08:29:04

John Gibbs’ link has some useful figures. The capital cost for offshore wind is around £3000/kw. If we would like to install an equivalent to Hinkley Point C power station with an output of 3.2Gw the capital cost would be £9.6 Billion. Looks better than ~£30 Billion for Hinkley point but the load factor for offshore wind is around 1/3 so we need 3 times as many turbines which puts the cost up to £28.8 Billion. Still not bad but the wind turbines have an anticipated life span of 20 years and Hinkley Point C has an anticipated life of 60 years. To produce 3.2Gw for 60 years using offshore wind would require a capital investment of £86 Billion rather than around £30 Billion for nuclear. This does not take into account the cost of alternative generation or storage systems for when the wind doesn’t blow. Where would I put my money?

The second problem here is the anticipated service lives. Nuclear power plants have easily exceeded 40 years service life and continue to be granted life extensions. Wind power and especially offshore wind has a poor track record.



Best regards


03/04/2018 15:55:02


The estimated £70 Billion is to decommission the all the nuclear power stations and all the nuclear debris left over from bomb manufacture (not part of civil nuclear power). If you calculate the output of the civil nuclear power stations over their life span the decommissioning cost is around 4p/kwh.

Here are some abandoned wind turbines:


Best regards


03/04/2018 14:44:55

Wind turbines do have significant maintenance and decommissioning costs. Up to now decommissioning has been simply ignored, when they break or are no longer profitable as the subsidies drop they are just left to decay.

The installers should be require to put the money up for removal back to a greenfield site. Bringing the big cranes back and removing the very large lump of concrete is not trivial in cost or environmental impact. This is very conveniently ignored.

There are already solutions for dealing with used nuclear fuel however they are in general not being implemented. Current nuclear power reactors are incremental developments of the reactors used to make plutonium for nuclear weapons. To produce the required quality they were designed for low burn up, in other words very little of the fuel is actually consumed. If the fuel is left in for a longer time different plutonium isotopes are produced that are not suitable for making bombs. Currently very little of the used fuel is reprocessed to recover the reusable fuel. There are also reactor designs with much higher burn up that can also use other materials from the spent fuel rods. Around 95% of what is generally called nuclear waste is actually a useful fuel.

I agree that used nuclear fuel is a very hazardous substance which requires specialized control and handling but the actual quantities are very small. A 1Gwe nuclear power plant will produce around 10 tonnes of used fuel per year. In view of the densities of the materials that is around 1m3.

Thread: Fabrication of solder wires
19/03/2018 11:16:53

An old work collegue of mine used to extrude relatively pure lead (mostly from cable sheaths) for making ammunition. If I remember correctly the barrel of the 'extruder' was around 30mm diameter and the finished rod was around 10mm diameter. The extrusion was done with a normal workshop hydraulic press and was carried out cold.

The extruder body and ram were steel, the die was just a hole.

Best regards


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