Member postings for John Lovegrove

Sorry not to have replied sooner, I have been busy with some other things the last couple of days. Concerning Niels mention of the SAE paper, I did download a copy of this and was quite surprised about how well the hot bulb engines compared with the diesel and spark ignition engines tested. The one doubt I have is that the author is clearly analyzing information from tests carried out by others and has drawn an arbitrary distinction between "hot bulb" and pre-chambered diesel engines (presumably with glow plug heaters for starting.) He works on the basis that an engine with a compression ratio of less than 13:1 is hot bulb and above this it is a diesel. Most people would regard a "hot bulb" engine with a compression ratio of more than 6 or 8:1 as a "semi diesel".

Regarding the terminology; in English "hot bulb" and "semi-diesel" are the words normally used. I know that in German they use the term "Gluhkopf" which means glowing head - similar to your own terminology.

Jens Erik - thanks for the information on museums.

John

Thanks Jens Erik

I did not realize that there were so many manufacturers of hot bulb engines in Norway. I had heard of Dan, Grei, Rap and Wichmann, (I saw one of the latter in a visit to your country in 2008.) It seems that almost every significant port had someone making these engines.

We will be visiting again in July this year, are there any museums or collections that I should try to visit?

John

I will just try putting in a couple of photographs to see that it works, This is the Bolinder B or W engine:

This is the earlier E type which used water injection:

And the M type with air injection (not sure how it fits in chronologically) the air compression is seen at the end.

Anyway many thanks for all the information you have supplied and good luck with your full diesel. I will try posting a response to the Norwegian gentleman who participates in the forum, to see if he knows any more about Bolinder.

John

Hello again Roger,

Thanks for the information on injection timing and compression ratios.

I had not seen this dual pump and glow plug arrangement before. I have been to the Paderborn museum in Germany where they have a large collection and there are tractors with the Zundkerze and ignition coil but I don't think they have any with the dual pump/dual injector + Gluhkerze arrangement. I have seen the use of a glow plug mentioned in connection with the higher-compression halb diesel that came later.

I did have some correspondence some time ago with Andy Watson who runs the Lanz Bulldog register in the UK and he mentioned the pendulum type electric starter that seems to mimic the hand starting process. I assume they did this to reduce the size of motor (and battery) required compared with something that would take the engine all the way over compression - or maybe there was a more subtle reason?

The tractor near us has a rotating dial to indicate the engine direction. I have read stories of the engines spontaneously reversing when running at low speed so I can see the need for something of this kind (although you would probably realize fairly quickly if you started to go backwards!?)

Do you have any further comments on Bolinder engines or is the Lanz your main area of interest?

As an aside - what do you have to do to add pictures to a post, I have tried copying on to the clipboard then using Ctrl +V in the little window that comes up, but it just does not work for me. Is there something I am missing?

Thanks again and best wishes

John

Thanks again Roger,

I started a reply earlier but had problems adding a photograph, then lost everything - so I will start again.

The information I have on the Lanz says essentially the same but in much less detail. I have also been trying to fill out the picture on use of petrol in these engines. They seem to have a version to run on this on a normal basis (although it is hard to imagine why anyone would want to do so.) What seems to have been more normal is using petrol to start up, then switch over to a heavier fuel once the key parts were hot enough - avoiding the need to use a blowlamp to heat the bulb. My understanding is that petrol was injected using the same injector system as the normal fuel and that they had a spark plug giving a continuous stream of sparks (like one gets from a trembler coil) so that ignition occurred when enough air had entered the head section to form a combustible mixture. I did talk to someone who has a lot of experience with these tractors and apparently this was hard on the engine and crankshafts have been bent or broken using this method of starting.

Any comment on this would be appreciated.

A couple of other points where I have been trying to get more "solid" information are compression ratio and injection timing: I have seen numbers of 6 or 7 : 1 for the compression ratio an 160 deg. before TDC for the start of the injection. Again any comment would be appreciated.

Turning to the Bolinder engine: I do have a manual for their B & W type engines and this shows essentially the same combustion chamber arrangement as your picture (but the design is slightly different.) This general arrangement seems to be the one they ended up with after a lot of development work and several different design iterations. Prior to this there was an E type (which is like the illustration in the Wikipedia article on hot bulb engines) and an M type that appeared ~ 1915. This had an air atomization system for the injected fuel. In the E type, water was used to suppress pre-ignition under load but there was a very clear incentive to avoid the need for this and the variable spray injector used in later designs seems to have achieved this objective.

One other thing they did to help maintain an adequate combustion chamber temperature during idling was to throttle the flow of scavenging air to the cylinder. This would have reduced the cooling effect of the incoming air. This approach was also used by Kahlenberg (and maybe others.)

What I have no been able to do is piece together the the chronology of these developments - and what else they might have done along the way. Again, information on compression ratios and injection timing are hard to come by. All the B & W manual mentions is injection starting about half way through the compression stroke. An estimate of compression ratio could be obtained by making a proper drawing from the sectional drawings given in the literature, then doing the calculations. But so far I have not done this.

I will try to figure out how to add pictures so I can share some of these but I will not try here and risk losing what I have posted so far.

Once again, any information you can provide to fill in the gaps in my understanding, would be appreciated.

Best wishes

John

Ther

Thanks Roger,

I did not know about the models made in Italy, the craftsmanship looks to be extremely good.

Someone fairly close to us has a Lanz Bulldog tractor (1949 I think.) I have seen this working and actually driven it. I have also made copies of the various manuals he has. Along the way I have acquired a couple of books on the Lanz but not the one you have.

While in the UK I have visited the Museum of internal Fire and the Anson Engine Museum, both places have several hot bulb/semi diesel engines operating. (Anson has several very interesting ones that are not running.)

I have assembled some information on American made engines and there are several operating in museums over here (e.g. Coolspring.)

Where I am really lacking is on information about the Scandinavian engines thinking particularly about Bolinder which was a major manufacturer and where it is hard to to find very much on all the development work they must have done.

The other area where I have assembled quite a lot of information is on the early work done by Akroyd Stuart. Here there is quite a lot of literature, but you have do dig fairly deeply to find items of significance.

Anyway.. I am very happy to swop information with anyone who is interested.

Thanks again

John

I am a retired engineer, formerly from England, now living in Canada, and my main model engineering interest is building model internal combustion engines. I used to subscribe to Model Engineer but the distribution in Canada became screwed up and I let the subscription lapse. (Our club now subscribes to Model Engineer' Workshop.)

As my next project I am planning to try a hot bulb/semi diesel engine and over the years I have been assembling information on these. In fact this has taken on a life of its own.

I know that Find Hansen in Denmark has made some of these and someone told me recently that something appeared in Model Engineer earlier this year about building one. Could anyone comment on this?

One of the things I have been trying to properly understand is the approaches used to cover a range of engine loads: Stuart Bridger posted some information about what Bolinder did in their later engines. I was aware of this system but do not have many details. The Lanz Buldog tractors had a somewhat similar arrangement but it worked the other way around.

Anyway, if anyone would like to get involved with a discussion around hot bulb/semi diesel technology I would be very interested.

John Lovegrove