Member postings for Roger B

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.

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

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

I believe this is the same as Coleman fuel.

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

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

Still following along and enjoying

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.

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.

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.

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.

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.

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

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).

I have an MF70 and made this video of drilling a 3mm hole in mild steel as a 'Show and Tell' for another thread on here:

**LINK**

I think you will find it a pain to use for regular drilling due to the screw feed rather than lever feed. I have a TBM 220 for small drilling work.

**LINK**

In other threads people have spoken highly of the BFW 40/E system but I have no personnal experience of it.

**LINK**

Another posibility is Teco who still produce the Hobbymat:

**LINK**

This is also available from Pro Machine Tools who advertise on here:

I think that the answer depends on how you cut the valve seat. If it is cut from the valve guide bore the concentricity of the guide doesn't matter. if it was cut from the the bore in the cylinder head then concentricity is important.

That looks to be in excellent condition What accessories did you get? I can see the 3 jaw chuck and the drill chuck as well as what looks like the milling angle plate in the background.

I think, and this is seriously stretching my memory that L T C Rolt produced a book on the development of machine tools and especially averaging devices to improve lead screws (I am prepared to be completely wrong on this ;-( )

Looks good I hope there are no hidden faults.

Looks and sounds great to me 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?

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.

**LINK**