Member postings for Roger B

This locking action is a result of the slightly strange (but actually quite clever) way the slides are adjusted.

The carriage is normally expected to move so the outer two screws are tightened so it just won’t move and the middle screw is then used to open up the gap until the carriage moves smoothly and without excessive play. This means that the clearances are smallest at the ends, reducing the tendency of the carriage to rock, and requiring the middle screw to be undone (anticlockwise) to lock.

The tailstock is fixed during normal operation so it is opened with the rear screw until it will just move and is clamped in place with the front screw, hence tightening (clockwise) to lock.

Built up crankshafts are fine. Silver soldering will work as will Loctite.

Compression allows for higher output and efficiency. The higher the cylinder pressure before ignition the greater it will be afterwards increasing the force on the piston and hence the output. The efficiency of an engine depends on the temperature difference between the maximum temperature at combustion and the exhaust temperature. The greater the diference the higher the efficiency. The maximun temperature and pressure are related which is why diesel engines with a high compression are mor eefficient then petrol engines which need to run lower compression to avoid pre-ignition.

For model engines the actual compression is not so important what is critical is that there should be minimal leakage. You say that you don't feel much compression. Does it feel 'springy'? Can you bounce the piston off the compression? This engine is a little smaller than yours but will hopefully give you an idea of what I mean.

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The method I use mills the cam using a series of tangents so various angles can be used. I set them out on a spread sheet with the angle and depth of cut, ticking each one off when complete. There are various programmes around for generating the steps from the cam data.

This engine was built on a minilathe using a vertical slide. I initially used an O ring to seal the piston but later made a cast iron piston ring.

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This is my first cam milling setup using a vertical slide. The blank is indexed using a 60 tooth changewheel with a paper degree scale stuck on. The depth of each cut is set using a DTI at the back of the cross slide and the slides are 'locked' with a G clamp. I now do much the same on a milling machine. The maching marks are cleaned up with a swiss file before hardening.

Yes you are quite capable. There will be a few 'trial' pieces as you learn but you will get a working engine. I would recommend an overhead valve four stroke as this separates the various problems. The cylinder on a two stroke has al the difficult parts in one piece. One mistake and you start again.

The key is the quality and fit of the bore and piston. This will probably require a couple of goes (at least). Cams are not a real problem for small engines unless you are going to race or fly them. Most model engines run a few hours per year. Cams and followers can be made from silver steel (drill rod) and hardened and polished. Mine are made in a series of steps on a mill but careful filling to a paper template should work ( a lot of experiments on full size engines were made in this way).

Give it a go, there will be plenty of help and advice available on the way.

Thank you Tim,

I fully understand the problems of scaling real life and am learning the additional problems that come with two strokes. I will be happy if I can get a operating range between 2000 and 4000 rpm. A 500rpm idle is out of the question. It sort of runs but the injector atomisation requires some more work.

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Some of the RC machines translations are also a bit strange, I use English and German (and live in Switzerland).

Looking at you machines you are working in the smaller sizes.

These people are good for small screws etc. but only in French, German and Italien (also with some dubious translations.

https://micro-model.ch/de/812-miniaturschrauben

Another supplier for small bits but again the translations are not complete.

https://www.mikromodellbau.de/artikelauswahl.php?kid=173&sprache=2

Conrad may be with a look:

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Some of the catagorie are a little strange in English. Most of the useful materials are in 'wood, timber, wood pieces' and then in profiles.

This is the clamping screw:

There are quite a few pictures on here which may help you to identify what you had:

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My brother has a tender locomotive and I have a stationary engine.

These people have them, but I don't know if they can deliver to the UK at the moment.

https://www.maschinen-werkzeuge.com/de/spannzange-er16-o-12mm.html

The first question I would ask is what are you going to do with the engine? If it is going to idle for a few hours a year at a show mild steel will be fine. If you are going to haul passengers with it in an 1831 every other weekend then you will need to use something better.

Splendid job

There was some discussion about this on another forum. The key points for good hit and miss operation were low friction and the quality of the firing stroke, a good hit is required. You may need to experiment with the mixture and timing to find an optimum. If you can apply a load to the engine to keep it below the governor speed adjustment may be easier.

Thank you This is my first go at a two stroke and bought a number of challenges. The prototype has angled ports, drawing these and the susequent maching was interesting. I strarted with an aluminium piece with the same dimensions as the cylinder but much shorter. This gave me a chance to see what was going on and reduced the amount of scrap. Using small long series milling cutters results in some deflection.

I cheated with the reed valves and bought a comercial set (spare part for a scooter, less than £2) which fitted in the space that I had.

I initially ran the engine as a spark ignition petrol engine to confirm that the red valves and ports actually worked.

Lots of fun

Very impressive work on the gearbox

There seem to be very few people building land vehicles powered by self built engines. There are a lot of ETW Wallabies out there but very few 1831s. I have seen a number of Lanz Bulldog derivatives. I think someone makes casting sets.

I am working (very slowly) on a couple of models. One will be powered by a 12cc four stroke twin. I have almost got the engine running to my satisfaction with a constatnt depression carb. The simple carbs tended to struggle when a load was applied. This will be a freelance design.

The engine on it's test bed

The second one is based on the Field Marshall horizontal single cylinder two stroke diesel. I am slill learning/experimenting with the injection system. I have acheived some firing but not sustained running.

There appears to have been at least 3 different designs of coupling used. I found this company when looking to upgrade my MF70 to ER 11 collets. I decided that the price was a bit high and instead I may purchase a plain shank ER11 chuck and machine the top to take the Proxxon coupling.

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What is your coupling like? This is mine:

In an attempt to add more confusion. The FF/PF 400 (FF was freestanding, PF mounted on the back of the PD 400 lathe) appear to have had two types of collet. The early one looks a bit like an OZ but I think was a Proxxon own design is shown here as part number 24252.

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The later machines used normal ER20 collets. The changeover from the old style is mention at the bottom of this site:

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A German owner of an older PF 400 ordered the newer ER20 spindle from Proxxon complete with bearings and tolerance washers for around €100 (in german).

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The Proxxon spares site (in english) is here:

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Roger

That's an impressive engine. Did you run it much? Is that a fuel or oil pump next to the carb? Is the camshaft chain or gear driven?

Excellent, One of the rather rare IC locomotives powered by a home built engine.