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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: Mc Donald Model tractor
25/07/2022 09:42:11

Still following with interest having spent several years playing with small fuel injection systems smiley

Thread: Loco transmission
23/07/2022 17:35:18

Is it possible to make the gearbox output coupling easy to disconnect? Possibly one of those couplings with two chainwheels and a short length of duplex chain, 4 cap heads and a couple of splitpins and you can tow as fast as you like.

23/07/2022 06:54:15

Have you asked Alan Keef, unless that's who you are working for wink

Homepage (alankeef.co.uk)

They have supplied many NG Locos

Thread: Mc Donald Model tractor
29/06/2022 10:00:19

That looks good smiley

Thread: Centaur Valve Timing
15/06/2022 20:06:08

So many tolerances will affect the valve timing. For a slow speed engine the timing is not very critical, with good compression and good ignition it will run.

Thread: hobbymat bfe65 sleeve guide broken
15/06/2022 07:26:43

TECO in the Czech Republic still make the milling machine. They may be able to supply the part you need:

http://www.tecoznojmo.cz/english/vf400.php

Thread: Threading 1.2mm S.S. rod (wire)?
06/05/2022 07:08:47

I have used stainless steel TIG welding rods. You just need to find a friendly welder unless you want to buy 1kg.

Thread: High Speed Bench Drill?
25/04/2022 19:53:35

As a quick show and tell I drilled a 0.3mm hole through a piece of 2mm brass using a Proxxon 0.3 mm drill bit at 8 000 rpm. The Rohm chuck held that with no problems but would not hold a 0.2mm bit (I generally used reinforced shank at 0.2mm or less so it is not a real issue.

0 point 3 mm hole.jpg

24/04/2022 11:12:34

I have owned a TBM220 with the Rohm 6mm chuck for a few years. It is generally good but at the price has obviously has some limitations:

- The feed is by a crank and rod rather that a rack so it is not linear.

- The column and base are not very rigid so with high drilling forces there is some deflection (but why would you be using high feed pressure on such a small machine?)

- The size range of the collets is limited however the Rohm chuck is good.

On the plus side:

- The play in the quill is adjustable.

- The simple depth gauge works well.

- The Proxxon short series drill set suits the machine well.

- It works well for tapping with the drive belt removed.

I always have the X-Y table fitted and also have the simple rotary table.

092 drilling the ends of the adjustment slots 2mm.jpg

Thread: Mc Donald Model tractor
19/04/2022 09:57:02

Good luck for the pour yes That's a complex piece.

Thread: Rumely Oil Pull engine
01/04/2022 13:08:13

I initialy tried running my 'petrol' engines on cooking alcohol as it did not smell as bad as pump petrol. They were stored in a shared cellar so that was important. I soon found problems with corrosion on delivery valve springs and injector needles.

A change to 'alkylate' fuel from the local agricultural merchants (not cheap at around CHF 20 for 5L) solved the problems. No smell and no corrosion smiley

I believe this is the same as Coleman fuel.

Thread: Mc Donald Model tractor
25/03/2022 15:41:21

I mentioned a little bit about my diesel at the start of this thread however things have moved on. I have been experimenting with fuel injection for some time and have successful manifold injection systems for Petrol/Gas/Benzin. The diesel injection system appears to reach around 100 Bar but good atomisation is proving difficult. The initial engine was a horizontal two stroke based on the Field Marshall design.

The two stroke diesel would start and run on standard automotive diesel fuel. I believe that an amount of the running was on fuel that had passed by the piston and was vapourised in the crankcase. This was backed up by the amount of oily black clag that comes out of the exhaust and the lack of response to the fuel rack position once it starts.

I am now rebuilding it as a four stroke to allow me to better separate the different parts of the operation cycle. The bottom end and conrod will be retained along with the lubrication system. It will need a new cylinder block piston and cylinder head. This is being documented on Model Engine Maker:

https://www.modelenginemaker.com/index.php/topic,10605.0.html

Here is a video clip of the two stroke nearly running and the initial layout of the four stroke. The stops were due to me reducing the fuel injection quantity. It has a tendency to run away but the air intake is easily blocked with a finger.

https://youtu.be/1OP6LxPb2uU

four stroke diesel.jpg

24/03/2022 15:44:44

I don't think that hot bulb engines used cartridge start as you didn't have to get them over compression. They were typically bounced off compression in the wrong direction and hopefully started running in the correct direction of rotation.

Cartridges as far as I know were used for starting full diesels where they had to be got rapidly over compression.

If I get my diesel running well I suppose a blank .22 cartridge could be an option wink

15/03/2022 12:36:28

Still following along and enjoying smiley

Is there room to fit an automotive diesel glowplug in the combustion chamber for the first trials? It could remove some of the uncertainty as you know it will be hot enough to ignite so you can concentrate on the fuel injection.

Thread: Hand Hacksaw
01/03/2022 14:11:13

Having looked to see what the fitters at work used I decided to buy one of these:

**LINK**

Interestingly the blade is held by screws rather than pegs.

new hacksaw.jpg

Thread: Mc Donald Model tractor
12/02/2022 07:03:36

A hot bulb type engine following the Akroyd Stuart design injects the fuel very early, around 150° before TDC, to allow for vaporisation. As the compression ratio increases and the engine moves towards Diesel's design the injection point moves nearer to TDC. The firing point on a hot bulb engine is more dependant on the cylinder head design than on the point of injection.

As long as the injection system is fairly symmetrical the engine will happily run in both directions. Some full size injection pump cams are deliberately asymmetrical to avoid the possibilty of starting in the wrong direction.

11/02/2022 15:38:03

I'm glad to try and help. This is a Lanz governor showing the intermediate excentric and the two spring groups, one for idling and one for maximum speed.

lanz governor.jpg

10/02/2022 07:42:24

Thank you for the diagram.

I am still not sure that I fully understand. Hot bulb/semi diesels are generally not very sensitive to injection timing. The lever system in the bottom right appears to limit the return stroke of the pump which would control the injection quantity but would also affect the timing.

I am more familiar with the Lanz system which has a similar looking governor but the weights rotate an eccentric sleeve inside the main eccentric that controls the pump stroke. Engine speed is controlled by a wedge between the eccentric rod and the injector plunger.

lanz fuel system.jpg

08/02/2022 06:56:03

Is there some separate form of stroke/volume control for the injection pump or do the weights also control the injection volume?

Thread: Remote starter system - identifying parts
02/02/2022 15:43:07

I think the sprag Clutch is there so that if the pinion doese not disengage from the flywheel gear when the engine starts the whole shaft is not driven at some thousands of rpm (depending on the gear Ratio).

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