Member postings for Roger B

Glad to hear that you have had it running Did the governor system work or haven't you got that far?

I think this is the rolling ring drive you are refering to:

Uhing® - Rolling ring drive: principle, advantages, product catalogue

That sounds about right A quick check suggests I have at least 9 injector designs plus five injection pumps. You will get there and it's great when you do

Looks good

What engine and transmission are you using?

Have you managed to get it firing in hot bulb mode yet or are you still experimenting with the injection system?

A chance to practice your German and some good pictures and diagrams of rack systems:

Zahnradbahn/Fahrwege und Fahrzeuge/ Wetzel (swetzel.ch)

Nothing looks as badly worn as the Snowdon example. There are ester based biodegradable lubricants that can be used even in Swiss Mountains.

I had a look through my pictures to see what racks were fortuitously there. There is one of the depot at Vitznau and one on the Geisbach railway. Both are Riggenbach and virtually unworn. The rusty pictures are slightly confusing. They could be the points section of a Riggenbach system or an Abt system.

I live in Switzerland and travel fairly often on rack railways. Generally they are well lubricated and I have seen nothing like that

That looks good Are the gas jets screwed in so you can easily change them?

I couldn't find this video clip yesterday. I didn't realise how old it was This is a confirmation of the quality of atomisation with a needle injector like the one above. As precautions there is a damp towel just out of view and a 1kg dry powder extinguisher by the door

https://youtu.be/jpkbryz4h78

What injector pressure are you looking for? I am using 90-100 bar (estimated) but you shouldn’t need anything like that.

I think that you need to reduce the length of your 0.35mm nozzle hole on two counts. Firstly the relatively long thin passage will tend to cause the atomised fuel to coalesce and secondly drilling a 0.35mm hole several millimetres long is a significant challenge. I would suggest the nozzle hole should not be much more than 0.7mm long (2 x d).

The long 1mm fuel passage will also be somewhat of a challenge to drill. I avoided this by having a long reduced diameter section on the needle but that makes whole thing longer and the fuel inlet somewhat clumsy.

Finally I moved on to the mushroom/poppet design which removes a number of the manufacturing challenges and avoids the fuel drain.

I designed my pump based on a 20 cc cylinder and a 14-1 Air Fuel ratio. This gave a fuel requirement of 2mm³. With a 2mm diameter plunger the calculated stroke for full power is 1.5mm.

The finished pumps have a bore of 2mm and a maximum working stroke of 2mm. The actual stroke is reduced either with a wedge or a helix spill to around 0.6mm for a light load.

If I remember correctly your engine is 80 cc so you would need to consider a maximum fuel delivery of 8mm³, so maybe a 3mm / 1/8” plunger.

I made my own simple test pump and use a spring balance to determine the approximate opening pressure of the injectors. It is also good practice at getting the required plunger fit to achieve the injection pressures.

BS1363-1 states:

A plastic earth pin on a moulded on plug for a class II (double insulated) appliance with a two core cable is perfectly acceptable. What purpose would a metal pin serve?

Current plugs are required to have sleeves on the live and neutral pins to avoid possible contact with thin metal objects before the contact is broken. People with arthritis or other hand mobility problems have been known to slide an knife between the plug and socket to get it out.

I use the term ‘True Diesel’ to distinguish this engine from the model aircraft type which use a carburetted ether fuel mix. I am following two of Diesel’s principles for an efficient internal combustion engine, the compression of pure air and the self-ignition of the injected fuel due to the temperature of the air. He also proposed that combustion should be a constant pressure, although in reality I don’t think this was ever truly achieved, and the maximum expansion of the gas during the power stroke.

His first experiments were with solid injection of light fuel oil (kerosene) as the planned heavy oil was too difficult to handle. He was unable to achieve good enough atomisation to get a controlled burn and controlled pressure so he moved to air blast injection.

The helix plunger is made from a piece of a hardened and lapped pin gauge. I started out using hardened and lapped silver steel but after some problems with a trilobed piece I moved to the pin gauge. The helix is ground using a Proxxon hand tool in my Hobbymat lathe with the change gears set for 4mm pitch. The other end of the helix is annealed and threaded M2 for the tappet.

I have mentioned my diesel experiments a few times in the McDonald Tractor thread. As I have now reached the first milestone I will write it up separately.

The work started a few years ago to try and build a 20cc horizontal two stroke diesel for a ‘Field Marshal’ type tractor. After a lot of experiments with the fuel injection system it sort of worked but I felt that it was running on the fuel that blew by the piston rather than the atomised injected fuel.

To resolve this I decided to convert it to a four stroke. The resultant is a bit of a compromise as the crankcase and lubrication is designed for a two stroke. The compression pressure is around 30 bar and the injection pressure is around 90 bar (calculated from the force on the test pump plunger) with a 2mm bore helix controlled pump and poppet style injector. After some experiments with the injection timing it runs and responds to the position of the fuel rack but also blows out quite a lot of unburnt fuel so I think I need to further improve the atomisation.

This video is of a warm start, gradually moving the rack towards open until it fires. It is running on pump diesel without additives.

**LINK**

I have been playing with fuel injection systems for many years. My current system seems to work and seems to be reproducible. This is based on 20 – 25 cc engines and uses a 2mm diameter injection plunger with a helix metering groove. I initially tried a needle type injector but the leakage by the needle was too much. I am now using a mushroom/pintle injector which seems to work well on petrol, as manifold injection, and diesel. I have built a test pump which I can operate with a spring balance which implies an injection pressure of around 90 bar. Be careful with fuel at these pressures and keep it away from your skin. I usually check the results against a piece of paper.

Here is an exploded view of my injection system. The injector needle is 1.4 mm diameter. There are more pictures on here:

https://www.flickr.com/photos/153503473@N05/

And a spray patten is here:

**LINK**

Great that you got it running I initially ran my two stroke diesel as a spark ignition engine to prove the porting as well. I have drilled nozzles down to 0.2 mm (8 thou) with my basic equipment. Did the original tractor have an open injector or some form of needle/pintle?

Thank you

Here's a brief clip of it running. Still lots more to improve.

**LINK**

You may want to think about some means of restraining the tractor when using to drill for starting. This gives you a hand free for adjusting the injection volume and timing.

I finally got my four stroke diesel to run at the weekend and it was trying to escape from the 'workmate' type bench I use for trials.