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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: Rumely Oil Pull engine
15/10/2021 10:57:17

Looks and sounds great to me smiley It is interesting that it seems to run better under load. Maybe the compression ratio is a bit to high for the weight of the flywheel?

Thread: Cutting Brass Sheet
02/09/2021 15:45:37

This is the closest example I have of what you would like to do. This was 0.3mm Phosphor Bronze. I have cut up to 3mm thick Brass.


01/09/2021 15:20:57

I use one of these small Proxxon saws with a HSS blade for cutting brass, aluminium and thin steel. You would need to check the clearances if you are working with larger sheets. The fence will go either side of the blade.

saw 1.jpg


saw 2.jpg



Edited By Roger B on 01/09/2021 15:22:07

Thread: Mc Donald Model tractor
26/07/2021 11:47:46

My engine is only 20cc so those valves are a bit big but that will hopefully help the volumetric efficiency.

25/07/2021 17:54:52

I'm still following and enjoying smiley

I decided to reduce the doubt for my two stroke diesel by using a commercial reed valve from a moped/scooter. This was not expensive however if you have a dealer/workshop near you you could see the various sizes and shapes available.

251 commercial reed valves.jpg

252 possible fit 1.jpg

252 possible fit 2.jpg

Thread: Centaur Ignition Coil
23/07/2021 15:31:30

The smaller size traditional motorbike coils are available from places like here:


I have used them sucessfully on my model engines.

Thread: Carb for single cylinder engine
02/07/2021 11:42:44

The fuel pump started out as a piece of 20mm square aluminium. I have also built a larger 25mm version but the delivery was too much for this engine. The diaphragm is cut from 1mm Viton sheet using the clamping ring as a punch guide. I decided to use a ball and socket at the rocker end of the pull rod so it would stop pumping against a closed outlet (needed for another application). It is driven by an eccentric mounted on the camshaft drive gear. The inlet and outlet are gravity ball valves with 3mm stainless steel balls. Tiny cross shaped pieces limit the movement to 0.5mm.

299 trial fitting.jpg

309 trial fit on the pull rod.jpg

312 valves in place.jpg

716 improved cooling pipe layout.jpg

fuel pump.jpg

02/07/2021 09:34:12

I made a tinplate float 26mm diameter and 30mm long many years ago. The material was the thinnest plate that the local model/hobby shop had, maybe 0.2mm. The ends were spun in the lathe and the body was rolled around a former. It was soldered up with the minimum possible solder to keep the weight down. The finished item weighs 6.5g and floats reasonably in alkylate fuel (I think the density is similar to pump petrol).

It never worked due to my inability to make a suitable valve at the time. I decided to use an overflow system for my model SU type carb as this would have needed an even smaller float and valve.

Tinplate float 1

Tinplate float 2

Thread: Easy Start
28/06/2021 19:22:36

No one will bother with Easystart if the engine will start without it. If you have to use easy start the engine already has significant problems. So no it is a myth. if you have to use easy start you will always need it, the engine is already past it's best. I will put in a caveat for very low temperatures but my 13 year old diesel car started instantly having been standing outside in -17°C for several days. The idling fuel consumption was ~4 times normal until the gearbox warmed up but we could drive away.

Thread: Hinckley C
16/06/2021 15:10:00

The problem at Taishan 1 appears to be within normal operational parameters:


08/06/2021 20:00:14

The problem is that the gas cooled reactors are much bigger than the water cooled ones and require more materials and end up with more activated materials to deal with at decommissioning.

There is a benefit that melting of the cores in case of accidents is less likely due to the lower energy density but where is the sensible balence ???!!!

Thread: Mc Donald Model tractor
29/05/2021 16:13:30

Excellent smiley

How many teeth are on the ratchet wheel, in other words what is the reduction from crankshaft speed? 3.2 x 3.4 mm is quite a lot of oil.

Thread: Hobbymat MD65 - help figuring out accessories (photos)
26/05/2021 11:58:40

As you say screwcutting takes care but it is possible.

The voltage regulator you show will not work with an induction motor as fitted to the MD65.

The slow speed system helps but is not the complete answer. The problem is the stopping time, the standard motor has quite high inertia and takes a while to run down when just taking a light cut.

Two possible solutions:

1) Make a handle to fit in the back of the spindle and turn by hand for screwcutting.

2) Change the drive to a 3 phase motor and inverter as described here:


Thread: What is a Lug Sweater?
20/05/2021 12:11:17

I think this is what he is talking about:


I borrowed something similar from work many years ago when rebuilding my bathroom. Wonderful, no flames, no smoldering floorboards.

Thread: Buying advice sought re Milling Machines: e.g. Proxxon: FF230 vs. BFW40/E vs. MF70
20/05/2021 07:07:08

I was using the Proxxon cutters, the 2mm cutter for the keyways was probably run at around 10 000 rpm with the feed as fast as I could turn the handle. The 3mm cutter for the rocker arms was probably run at around 8 000rpm with a slightly more gentle feed. No lubricant was used.

Thread: Hobbymat MD65 refurb' tailstock problems
10/05/2021 13:53:57

There should be two bolts under the tailstock. One (furthest from the headstock) opens up the slot and allows the tailstock to move freely, the other closes the slot to clamp the tailstock when in use. If both screws are released the tailstock will barely move as you have found.

Be careful with the slot opening bolt, you can crack the tailstock if you open the slot too much.

There is a similar arrangement for the crossslide but with 3 bolts, two clanping and one opening.

Edited By Roger B on 10/05/2021 13:54:32

Thread: Small saw. Proxxon or something else
09/05/2021 06:50:21

I got the new blades and tried them to make a couple of pieces I needed. One was a 25mm square from 0.5mm steel as a shim to go under the toolpost on my FD150 and the other was an 8mm wide strip of 0.3mm phosphor bronze for part of the injection pump on my twin cylinder engine.

Both cut easily and were true to better than 0.1mm. There was a small burr but both remained flat. The videos are here:

drilling 5mm.jpg

Thread: Hobbymat MD65
05/05/2021 18:37:28

I would also recommend installing start stop buttons to give a no volt release as were fitted to the latter machines.

Thread: motor control
05/05/2021 17:11:54

Connecting permag motors in series and parallel will give you 'low speed' and 'high speed' options, but as permag motors are more like shunt wound motors with a relatively constant field strength you won't get the full benefits.

Thread: Buying advice sought re Milling Machines: e.g. Proxxon: FF230 vs. BFW40/E vs. MF70
05/05/2021 15:15:10

As ever show and tell. These rocker arms were milled from 6mm square silver steel with a Proxxon 3mm end mill. The 2mm keyseats in a medium carbon steel crankshaft (ST50 maybe similar to EN8) and a silver steel camshaft were cut with a Proxxon 2mm end mill.

346 the third side.jpg

351 need fettling and threading.jpg

365 done.jpg

366 milling the camshaft keyway.jpg

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