# Hot Bulb Engine, here we go...



## cfellows (Jun 2, 2010)

Meager beginnings. I started with the injector pump. Find had an exploded view of (most) of the parts on his pump. He also supplied a couple of dimensions, so I took it from there. My ball check valves will be 3/32" compared to his 1mm. Also, my plunger rod will also be 3/32" compared to his 2mm. The rest of the dimensions are approximations with the square part being .25" and the round part 3/16". I'm hoping there is nothing other than close tolerances required to make this work. And I don't see how it could be more frustrating than my experience thus far with carburetors!

The injector also looks pretty straight forward and I think I have the hot bulb figured out. I don't know what materials he used for the hot bulb. I'm guessing stainless steel would be best but I may have to settle for mild pr silver steel for starters.

This will likely be a slow process since I have a number of other domestic projects that I can't seem to avoid, try as I might. I also will probably use more conventional gearing than Find's very nice helical gearing. Would love to make helical gears but that sounds like a project for another time (maybe another lifetime!). 

So, drift in and out from time to time and we'll see how it goes.

Chuck


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## Kaleb (Jun 3, 2010)

How do you plan to make the injector?


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## doubletop (Jun 3, 2010)

Chuck

Looks an interesting build. Are the plans available anywhere so we can see where your going or are you going to keep us in suspense?

Pete


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## cfellows (Jun 3, 2010)

No plans or drawings. All I have to go on are some pictures and a few descriptsions at Find Handsen's website:

http://www.findsminimodelhotbulbengines.dk/

I'm not going to attempt to build any of his engines, but rather come up with my own.

Chuck


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## doubletop (Jun 4, 2010)

Chuck

OK now you really do have me interested.

And we'll get some plans at the end..................?



Pete


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## shred (Jun 4, 2010)

IIRC there's also some useful information mixed into the original hot-bulb patents (linked off the Wikipedia page)

Unlike a diesel, the injector just has to get some fuel inside the cylinder and onto something hot, not actually vaporize it during the injection process (that's what the hot-bulb is for)


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## Deanofid (Jun 4, 2010)

I looked at that fellow's engines, Chuck. They look wonderfully complex. This should be a great
build thread. The newly made parts look nice.

Dean


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## cfellows (Jun 5, 2010)

shred  said:
			
		

> IIRC there's also some useful information mixed into the original hot-bulb patents (linked off the Wikipedia page)
> 
> Unlike a diesel, the injector just has to get some fuel inside the cylinder and onto something hot, not actually vaporize it during the injection process (that's what the hot-bulb is for)



Yeah, I had kind of figured that the injector only needed to get the fuel into the engine and onto a hot surface. I have to also think that timing is pretty critical. Find Hansen indicates that you also need a 7:1 or better compression ratio to help keep the hot bulb hot.

Chuck


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## cfellows (Jun 5, 2010)

Deanofid  said:
			
		

> I looked at that fellow's engines, Chuck. They look wonderfully complex. This should be a great
> build thread. The newly made parts look nice.
> 
> Dean



Thanks, Dean. Find's engines are pretty amazing, comprised of all the things that really pique my interest. I especially like the helical gears. I'm not anticipating building anything quite as complex as his engines, at least not at first. I've actually contemplated converting my Plumbing Parts engine over to hot bulb operation.

Chuck


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## Niels Abildgaard (Jul 17, 2010)

Hot bulb engines are described in a SAE paper 2002-01-0115 Olaf Erlandson from Lund in Sweden.
I worked on the last factory that made this kind of engines in the world in 1977 in Hundested,Denmark.
The final versions were crankcase scavenged two strokes of one or two cylinders.From memory the biggest single cylinder was 420 mm bore and 450 mm stroke.This was for fishing vessels and gave 150 horsepower directly to a two bladed screw that changed pitch to go astern.Timing of injection in the full size engines was not very critical and this was their main argument against real diesel engines.
Try Youtube Hundested hot bulb


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## njl (Jul 17, 2010)

Looking forward to this build Chuck. Your parts look good.

Neil your comments above bring back memories of a canal boat holiday I did a few years back when we passed a Bollenger powered working boat going the other way through the Braunston tunnel, that wonderful sounding engine coming towards us out of the darkness was just magic.

Nick


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## Niels Abildgaard (Jul 17, 2010)

Hello Nick

Firm was Bolinder,Eskiltuna,Sweden

Try( NB Severn at Braunston) Youtube


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## njl (Jul 17, 2010)

Cheers Neils,

Yep that's the sound, lovely, possibly the same boat. Sorry I got the spelling wrong, unfortunately, nothing new there then - note to self: it's Bolinder not Bollinger, close but no cigar 

Chuck I hope your engine makes a similarly distinctive sound too.

Nick


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## cfellows (Jul 17, 2010)

Thanks for the comments. I've been sidetracked on this project a bit while I'm figuring out how to make helical gears for the engine. Just about there, I think.

http://www.homemodelenginemachinist.com/index.php?topic=9916.0

Chuck


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## cfellows (Aug 12, 2010)

I'm really bummed about the hot bulb engine project. I had originally thought that the fuel was injected at or near TDC and that's what controlled the ignition timing. Now I find out that the fuel is injected into the hot bulb chamber during the air intake stroke and that ignition timing is controlled by when the air reaches the fuel vapor and the hot bulb. Sounds dicey at best and it could be very time and labor intensive to get this thing running. Aarggghhhhh! 

Chuck


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## Rustkolector (Aug 12, 2010)

Chuck,
Injection during the intake stroke doesn't quite sound right. Where did you get this information? The 2 stroke hot bulb engines used injection at mid compression stroke. I would think the 4 strokes would be similar.

Jeff


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## cfellows (Aug 12, 2010)

Got this from Wikipedia:

http://en.wikipedia.org/wiki/Hot_bulb_engine#Four-stroke_engines

It also appears on the Find Hansen motors that the injector pump cam lobe is timed about the same as the intake valve cam lobe.

Chuck


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## shred (Aug 13, 2010)

The patents also speak to injecting fuel during the intake stroke. They intake air separately from fuel-- fuel goes into the hot-bulb for vaporization, air into the cylinder. They don't mix until the compression stroke. At least one of the patents suggests timing is done by the ratio of the volumes and compression ratio-- get enough air into the hot bulb and you get ignition. 

http://www.google.com/patents?id=3n...=gbs_selected_pages&cad=1#v=onepage&q&f=false
http://www.google.com/patents?id=oe...=gbs_selected_pages&cad=1#v=onepage&q&f=false
http://www.google.com/patents?id=05...=gbs_selected_pages&cad=1#v=onepage&q&f=false

The engines seem so simple it doesn't seem like it would be that hard to get one going, but there might be a whole lot of trial-and-error tribal knowledge that's gone by the wayside. They do seem to have a pretty generous unswept cylinder volume, so you could install blocks and such to vary the compression ratio. I'm guessing the fuel-air mixture ratios needed to support combustion are fairly well known, but what other devils are hiding in the details, lord only knows.


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## cfellows (Aug 13, 2010)

Shred, to your point of generous unswept cylinder volume, I've noticed this and wonder how they manage to get the compression ratio high enough to generate additional heat.

Chuck


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## Dan Rowe (Aug 13, 2010)

Chuck,
I checked the web and my book shelf and hot bulb engines have several names. They are also called oil engines and semi-diesel engines. Lyle Cummins Jr. devoted a chapter to them in "Internal Fire". I glanced through the chapter and it is good information. This book is going for around $25 or less on Amazon.

I also found a cross section drawing of a Mietz and Weiss hot bulb engine in "Elements of Diesel Engineering" Adams 1936.

I should have looked sooner as I could have made the Austin Machinist Club meeting and brought the books for a discussion topic.

Here is a thread on a full size Mietz and Weiss engine:
http://gasengine.farmcollector.com/gas-engines/Start-Your-Engines.aspx

Dan


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## shred (Aug 13, 2010)

cfellows  said:
			
		

> Shred, to your point of generous unswept cylinder volume, I've noticed this and wonder how they manage to get the compression ratio high enough to generate additional heat.
> 
> Chuck


I'm not so sure they do generate much additional heat from compression anymore. I think ignition more or less happens when the fuel-air mixture in the bulb gets lean enough to burn. That burn heats the hot-bulb for the next cycle. Were I to try building one, I think I'd start with the always-on blowlamp version first.

Reading that story Dan linked, it seems like his was firing before the compression stroke was done, what with all the reversing it was doing until the flywheels got to cranking it all the way around.


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## Dan Rowe (Aug 13, 2010)

Chuck,
This is from my copy of "Gas Gasoline and Oil Engines" Hiscox 1897 Pg. 240-244







     "_The Hornsby-Akroyd Oil Engine_"
   "This engine is of English origin and now built by the sole licensees of the United States patents---the De La Vergne Refrigerating Machine Company---in all sizes from 4 to 55 H.P. They are of the four-cycle compression type, using any of the heavy mineral oils or kerosene as fuel.
   This unique explosive engine seems to be a departure in design from all other forms of explosive engines, in the manner of producing vaporization of the heavy oils used for its fuel and the mannor of ignition.
   An extension of a chamber from the cylinder head, somewhat resembling a bottle with its neck next to the cylinder head, performs the function of both evaporator and exploder. Otherwise these engines are built much on the lines of design as gas and gasoline engines, having a screw reducing gear and secondary shaft that drives the governor by bevel gear, the automatic cylinder lubricator by belt, and cams for operating the exhaust valve and oil pump.
   The bottle-shaped extension is covered in by a hood to facilitate its heating by a lamp or air-blowpipe, and so arranged as to be entirely closed after the engine is started, when the red heat of the bottle or retort is kept up by the heat of combustion within. The narrow neck between the bottle and cylinder, by its exact adjustments of size and length, perfectly controls the time of ignition, so that of many indicator-cards inspected by the writer there is no perceptible variation in the time of ignition, giving as they do a sharp corner at the compression terminal, a quick and nearly vertical line of combustion, and an expansion curve above the adiabatic, equivalent to an extra high mean engine pressure for explosive engines.
   The oil is injected into the retort in liquid form by the action of the pump at the proper time to meet the impulse stroke, and in quantity regulated by the governor. Durring the outer stroke of the piston air is drawn into the cylinder and oil is vaporized in the hot retort. At the end of the charging stroke there is oil vapor in the retort and pure air in the cylinder, but non-explosive. On the compression stroke of the piston the air is forced from the cylinder through the communicating neck into the retort, giving the conditions represented in Fig, 184 and Fig. 185, in which the small stars denote fresh air entering, and the small circles the vaporized oil. In Fig. 185 mixture commences, and in Fig. 186 combustion has taken place, and during expansion the supposed condition is represented by the small squares. At the return stroke the whole volume of the cylinder is swept out at the exhaust, and the pressure in the retort neutralized and ready for another charge.
   It is noticed by this operation that the ignition takes place within the retort, the piston being protected by pure air.
   It is not claimed that these diagrams are exact representations of what takes place within the cylinder; never the less, their substantial correctness seams to be indicated by the fact that the piston rings do not become clogged with a tarry substance, as might be expected.
   This has been accounted for by an analysis of the products of combustion, which shows an excess of oxygen as unburnt air; which indicates that the oil vapor is completely burned in the cylinder, with excess oxygen."
















Dan


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## Deanofid (Aug 13, 2010)

Chuck, can you make an adjustable cam for your trials? Until you find out the position the cam
is supposed to operate the injector, I mean. Possibly a lobe made by itself, with a couple of set
screws on a turned collar that will allow you to change the position of the lobe on a shaft that
drives the cam lobe. Then, when you find out where you want it, make a solid cam shaft.

Or, since you are driving the cam via gears, make one gear easy to rotate on its shaft, for
timing purposes.

This engine will run on a vaporous fuel, like gasoline or naphtha, right? It may not take a lot of
compression to ignite the fuel that's been super vaporized in something like a hot bulb. Seems
like it would just be begging to go off in an environment like that. 
Then again, maybe I don't understand this at all!

Dean


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## Rustkolector (Aug 14, 2010)

Chuck,
It is obvious Find's engine design is nothing like the early 2 stroke oil engines like Mietz & Weiss engines. The latter used very low compression amounting to about 60-65 psi. Injection was directly into the cylinder mixing with the air and ignited upon contact with the hot bulb. Ignition timing was highly dependent on hot bulb temperature which was controlled with the introduction of water vapor into the combustion air. Water consumption increased with load. While quite effective, the addition of water to the combustion air greatly added to cylinder wear. The 4 stroke design appears quite different. Find has moved the injector to the cylinder just like the 2 stroke M&W design, as he says, to keep the injector and fuel cool. However, it appears his added vaporizer tube catches the fuel stream and directs the fuel into the hot bulb where it vaporizes. The vaporized fuel and combustion air remain separated during the intake stroke. As the piston compresses the air into the hot bulb, the bulb temperature ignites the fuel, and combustion progresses. As the Hornsby-Akroyd article suggests, the size of the of the hot bulb orfice is varied to get the required combustion timing. I think this area of the hot bulb is where much of the trial and error will begin since Find's vaporizer tube passes through this orfice also. 

I own a Mietz and Weiss engine and I know the hot bulb must be almost a dull red heat before the engine will start easily on kerosene. Looking at the rather low intensity flame on Find's little preheat lamps, I don't see where he is putting that kind of heat into his hot bulb. That interests me greatly. 
Jeff


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## cfellows (Aug 15, 2010)

Shred, I have agreed more or less with your theory, that the mixture ignites once it gets lean enough.

Dan, the pictures you posted confirms what I had thought I understood about the full size hot bulb engines.

Dean, yes, I can make an adjustable cam lobe. I don't think, however, the fuel injection timing is as critical to ignition as other factors such as those that control the timing of the air reaching the vaporized fuel.

Jeff, I've studied Find's pictures ad nauseum, but it hadn't occurred to me that the vapor tube was set up to "catch and redirect" the fuel into the hot bulb. Very perceptive on your part, the design makes a lot more sense to me now.

As complicated as this all seems, I'm not sure why I continue to pursue this. Must be a glutton for punishment!

Chuck


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## b.lindsey (Aug 15, 2010)

Chuck, I have been following this with great interest even though I can't add to the discussion. If it can be scaled down it will make a fantastic and unique model, and with your perseverance I am sure that will happen.

Regards,
Bill


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## cfellows (Aug 15, 2010)

I've decided to pattern my hot tube engine after my Henry Ford Plumbing parts engine. I scored a couple of 9" flywheels, so I'm scaling up the engine to a 1" bore x 1 3/4" stroke. This engine design is good for this type of project because everything is open and easily modified, added-to, etc., as required.

The cylinder will be made from the 1" plumbing tee in the picture. I've bored out the inside to to receive a cylinder liner that is 1 5/16" OD. I also counterbored the inside of the plumbing tee to form a water jacket around the cylinder.

The flywheel is now mostly machined. I still want to thin the spokes some since they look way too fat for my taste. 






Chuck


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## cfellows (Aug 16, 2010)

Still another turn. I'm now thinking I'll convert my existing plumbing parts engine to hot bulb operation. The construction is such that I shouldn't have too much extra work to do and the the changes needed for the hot bulb should be pretty easy.

Here's a photo and drawing of the hot tube I made. It's patterned very much after Find Hansen's hot tube although I had to guess at the dimensions. The material started out as 5/32" diameter drill rod 1 1/4" long. The hole through the center is a number 40 which is around .098" in diameter. The cross drilled holes are 5/64". The single cross drilled hole in the other end will be drilled after I make the hot bulb assembly and thread the hot tube into it, since the cross drilled hole has to be on top. Or I may just drill a through hole in the end of the hot bulb and use a nut on the outboard end so I can rotate the hot tube as needed.
















Chuck


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## Dan Rowe (Aug 16, 2010)

Chuck,
I am glad that old text was useful. I think the key points made in it were the size and length of the hot bulb connection tube was the critical thing for ignition timing. 

Find's models used a long connecting tube so the metal connection to the cylinder would not cool the hot bulb to much. Or at least that was my take on reading the pages. 

It seams to me that if the connection tube was made from machinable ceramic the heat loss to the cylinder would be all but eliminated. The problem is all the machinable ceramic stock I have seen is a bit pricey.

The is a fantastic project and I will be watching your progress with interest.

Dan


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## shred (Aug 16, 2010)

Dan Rowe  said:
			
		

> Find's models used a long connecting tube so the metal connection to the cylinder would not cool the hot bulb to much. Or at least that was my take on reading the pages.


I was thinking that with a sufficient blowtorch on the outside of the hot bulb, faffing around with the remotely located vaporizer/injector could be done away with for a first engine  Good on ya for trying it Chuck.


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## cfellows (Aug 16, 2010)

The main reason, in my mind, for using the vaporizing tube is so the injector can be located away from the hot bulb and eliminate the need for water cooling the injector. If you place the injector on or near the hot bulb, you have to water cool it or the fuel in side will boil.

Chuck


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## cfellows (Sep 23, 2010)

Just a brief update to let people know I'm still working on the hot bulb engine. I've returned to the idea of building the engine from scratch instead of converting my plumbing parts engine. I've been wrestling with whether to make it a 1" bore or 1 1/4" bore. I've also been trying to come up with the best design for the cylinder / water jacket. I think I've got those questions settled as well. I've ordered the materials from Speedy Metals and should be getting that delivered early next week (tomorrow is probably too much to hope for!).

The engine frame will be made from 3/8" angle iron, 2" x 3". I've also settled on a 1" x 1 3/4" bore and stroke. I'm trying to keep the design as simple as possible and, at the same time, add enough bling to make it look nice. 

The valve manifold will be on the side of the head and the single valve will act as both exhaust and inlet valve. It will be opened at the end of the firing stroke and held open through the exhaust stroke and the intake stroke, closing at the beginning of the compression stroke.

I was going to incorporate helical gears, but decided that simple spur gears along with other simplifying measures might inspire others to build it, assuming I can get it to run!

At the moment, I'm planning to use flanged ball bearings for the crankshaft, but that may change.

Here's a stylized drawing of what it will look like so far.






Chuck


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## cfellows (Oct 7, 2010)

Couldn't stand it any longer, I had to get out in the shop and do something. So I made the cylinder liner and the water jacket. The cylinder is turned from a 1 5/8" hunk of cast iron and the water jacket was turned from a 1 3/4" piece of steel tubing. Kept the outer diameter the same, but had to bore it out for an interference fit over the cylinder linder. Not sure why the texture on the outside of the tube is rough, but I kind of like it... looks like cast iron. 

After all the indecision about whether to make it a 1" bore or 1.25" bore, I settled on .875" instead. The stroke will be 1.5"


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## swilliams (Oct 7, 2010)

Looks good Chuck

Just wondering about the interference fit since I need to do similar soon. How much interference did you make? Are you going to press it in cold or shrink fit it?

Cheers
Steve


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## cfellows (Oct 7, 2010)

swilliams  said:
			
		

> Looks good Chuck
> 
> Just wondering about the interference fit since I need to do similar soon. How much interference did you make? Are you going to press it in cold or shrink fit it?
> 
> ...



Thx, Steve. The ID of the water jacket is about .003" smaller than the OD of the cylinder liner. I will put the cylinder in the freezer and heat the water jacket as hot as I can get it with my mapp gas torch. Hopefully the cylinder liner will just drop right into the water jacket.

Chuck


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## NickG (Oct 9, 2010)

This looks really interesting chuck,

i've just scanned over it up to now but will have a proper read later.

Thanks for sharing :bow:

Nick


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## swilliams (Oct 11, 2010)

Hi Chuck

I did a quick calculation based on thermal expansion coefficients which I found here, 

http://www.engineeringtoolbox.com/linear-expansion-coefficients-d_95.html

If I have things correct then for steel of 1" diameter you need to heat it up by about 230 degs C to get it to grow by 3 thou.

I might try an experiment with shrink fitting a brass ring on a bit of steel rod before I move onto the real thing

Sorry for dragging you off topic

Cheers
Steve


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## steamer (Oct 11, 2010)

Chuck,

Steve's on the right track here....I get 213 C , or about 415 F


Dave


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## Rustkolector (Oct 11, 2010)

Chuck,
It would be a pain to find a leak after heat shrinking it together. Heat shrinking is better than pressing them together cold(relative to leaking), but silver brazing is quick and easy, and you are visually pretty assured of a complete seal. 

Jeff


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## cfellows (Oct 11, 2010)

Rustkolector  said:
			
		

> Chuck,
> It would be a pain to find a leak after heat shrinking it together. Heat shrinking is better than pressing them together cold(relative to leaking), but silver brazing is quick and easy, and you are visually pretty assured of a complete seal.
> 
> Jeff



Thx for the tip, not sure how successful I would be silver soldering cast iron to steel...

Chuck


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## Niels Abildgaard (Nov 26, 2010)

The real beauty of the scheme is that You can make a new cylinder with a single piston controlled hole or port and demonstrate something that has never been done before.I wish You swift progress and cannot wait.


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## Chaffe (Feb 15, 2011)

Hello, i have just registered after reading this thread. I find this topic very interesting and am currently in the process of building a model engine myself, i was going to go the conventional spark plug ignition route but always fancied compression/diesel ignition. Are you still going ahead with this build? I will be keeping an eye on this. James


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## compspecial (Feb 15, 2011)

Hi chuck, another wonderful and interesting project, I'm sure your mapp torch will have absolutely no trouble heating the part to a mere 230 degrees.
               cheers Stew.


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## Dave G (Feb 15, 2011)

Hi Chuck, very interesting build you have going on there. I'm anxious to see your hot bulb being built. It looks like it will be alot of fun. Nice to see others build their own designs. we can all benefit from it. Thank you for sharing and good luck with the build. Dave


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## kanvelchoudhary (Feb 15, 2011)

hi chuck. your new work seems just awesome as usual. you have always inspired me. after reading about your new project i noticed something is odd about your inlet and exhaust port. i am not sure whether placing the port on side is a nice idea since it is too close to both injector and hot tube and it might cause some heating problems. now as you mentioned only a single port will be serving the purpose of both inlet and exhaust ports so timing is a great issue. and even a slight change in dimensions due to over heating might disturb it all. what i suggest is that placing the port just beneath the injector. i beg your pardon if i have misunderstand your design and come up with some wrong issues. but i wanted to share my opinion with you. 
anyway all the best and i wish you will soon have that engine running.
kanvel


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## cfellows (Feb 15, 2011)

This project has been put on the back burner for a while. I want to get back to it at some point, but don't know when that will be.

Chuck


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## Edward Perera (Jul 13, 2019)

Hi, Chuck,
I joined the forum a couple of days ago. I am really interested in building a model hot bulb engine.
May I know how far you have progressed in designing and building your project?
Even though I have quite a good experience in building items according to plans, I believe that I do not have enough knowledge to design some thing new.
I would be grateful to you if you could kindly let me know whether you could advice me on this project.

Cheers, Edward.


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## Cogsy (Jul 13, 2019)

Hi Edward,
I'm not sure if Chuck ever finished this design or not, but unfortunately Chuck has since passed away.


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## Edward Perera (Jul 13, 2019)

Hi, Thanks very much for letting me know. So sorry to hear that...

Edward


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## Jennifer Edwards (Jul 14, 2019)

Is that anything like “Hot Tube” ignition?

I once restored an old farm engine that had a kerosene burner under a copper tube that was sealed on one end, the other was open to the cylinder.

You lit the burner, waited for the tube to get real hot, then primed and cranked the engine. 

If you were lucky it started without breaking your arm.


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## mortimer (Jul 14, 2019)

http://findsminimodelhotbulbengines.dk/twostrokehot-bulbengine.html

here's a 2 stroke hot bulb


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## Mechanicboy (Jul 14, 2019)

Jennifer Edwards - "If you were lucky it started without breaking your arm." 

I had the old Sabb semidiesel (hotbulb engine), to crank the engine was easy. 
Tilt the flywheel in both directions and turn the flywheel backwards fast before you get rid of. Then the engine starts in the right direction after the bounched start was performed.

Here is the Sabb who are easy to start up..


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## Edward Perera (Jul 14, 2019)

Jennifer Edwards said:


> Is that anything like “Hot Tube” ignition?
> 
> I once restored an old farm engine that had a kerosene burner under a copper tube that was sealed on one end, the other was open to the cylinder.
> 
> ...



The  hot bulb engine is fitted with an external chamber (bulb) attached to the top of the cylinder and the fuel is injected into it.


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## Edward Perera (Jul 14, 2019)

mortimer said:


> http://findsminimodelhotbulbengines.dk/twostrokehot-bulbengine.html
> 
> here's a 2 stroke hot bulb



Visited the site. It is a marvellous piece of engineering!!!


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## Mechanicboy (Jul 15, 2019)

Edward Perera said:


> The  hot bulb engine is fitted with an external chamber (bulb) attached to the top of the cylinder and the fuel is injected into it.



Not only direct into hot bulb..  The fuel is injected into hot bulb under idling and under full load, then the fuel is injected direct into the cylinder. You can see there is injection control handle so you can change between directly on hot bulb or directly in cylinder as i showed the movie of Sabb engine (top of cylinder where injector with handle are there, not where the man is fiddling with air starter valve on the front of cylinder). It's to preventing knocking and overheated hot bulb under load.


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## Edward Perera (Jul 15, 2019)

Mechanicboy said:


> Not only direct into hot bulb..  The fuel is injected into hot bulb under idling and under full load, then the fuel is injected direct into the cylinder. You can see there is injection control handle so you can change between directly on hot bulb or directly in cylinder as i showed the movie of Sabb engine (top of cylinder where injector with handle are there, not where the man is fiddling with air starter valve on the front of cylinder). It's to preventing knocking and overheated hot bulb under load.



Thank you very much for your kind explanation. I wasn't aware of this arrangement until now.


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## Racemybuick (Jul 15, 2019)

This is my father's hot bulb engine called a "charter."

It was an experimental prototype with very heavy flywheels, dual injector for multi fuel (runs on kerosene now) and has a heat exchanger in the exhaust. 

Cool stuff

John


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## Mechanicboy (Jul 15, 2019)

Racemybuick (John)
The "Charter" engine is near same as Mietz and Weiss engine.


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## Racemybuick (Jul 15, 2019)

Mechanicboy said:


> Racemybuick (John)
> The "Charter" engine is near same as Mietz and Weiss engine.





It's funny you mentioned that... The charter was a product of Mietz and Weiss post bankruptcy it "buyout".  After Weiss closed, Charter continued several models until collapsing in the 60's.  This was a later model that was used in a college, or so the back story goes. 

John


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## Mechanicboy (Jul 15, 2019)

John, exactly,.. i saw the engine was more same as Mietz and Weiss. I did no know the Charter engine was a continued product of the Mietz and Weiss.

I loaned the book "Hot bulb engines" printed in 1919, there was a picture of the large 3 cylinder hot bulb marine engine Mietz and Weiss, it has one pump only to distribute to all 3 cylinder, it has 3 cam lobe and one disc with 1 hole with other disc with 3 hole to distribute the fuel for each 3 cylinder. Also it's a distributor fuel pump.


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