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gbritnell
08-05-09, 11:35 AM
This is my version of a 1918 Holt tractor engine. I say my version because this one was scratch built like my 4 cyl. OHV engine. There are castings and drawings available for it through a supplier named Cole's Power Models. I had seen several built versions of the engine over the years and was fascinated by the exposed valve train and peripheral parts. I started by purchasing the drawings only to see what was involved. I had talked to several people who had built them and they weren't totally happy with the castings so I decided to cut it from bar stock. The original casting for the crankcase is one piece, which probably followed the 1:1 engine but it made it extremely difficult to machine the main bearings so I designed mine with a split crankcase for ease of building and maintaining. As with my other engines the bulk of this one is made from 6061 aluminum, nothing exotic but just a good aluminum to work with. To answer a question from the 4 cylinder posting, I don't do my own casting, that's another hobby in itself. Like Ken I scratch build most of my models. I did purchase the intake and exhaust manifolds for this engine as they were just too complicated to cut from solid. The crank is a stressproof type steel which means it doesn't distort when machined like most cold rolled mild steels. The original design only had a thermosyphon type cooling system, as the water gets hot it rises and therfore circulates itself. Here again I don't know what the designer had in mind but after the first few runs I realized it would need a water pump so I designed and built my own. This helped greatly but most of the running time is at lower rpm's so the engine would still get hotter than I cared for so next up was a fan, fan shroud and the mounting apparatus and brackets. I have about 1-1/2 years of build time on the engine and about 6months of tinkering, modifying and fine tuning to get it to where it is today. The bore is 1.00 and stroke is 1.25. It has points for the ignition trigger and uses an electronic ignition for the spark. This is housed in a box with a small 6 volt battery. The spark plugs I purchased commercially although I generally make my own with teflon for the insulators. It has a splash oil system. I have posted a couple of pictures in the gallery and will include a few more. These will be of the crancase I designed and built. I will also post the links to Youtube with it running. My digital camera takes good videos but the files are huge so it's probably better to use Youtube rather than try to get them on here.
gbritnell
YouTube - updated Holt video (http://www.youtube.com/watch?v=4ooTq2xF2pw)
YouTube - Hand starting the Holt model engine (http://www.youtube.com/watch?v=tl0nD1smbAg)

ScaleMotorcars
08-05-09, 11:59 AM
1clap11clap11clap1

Really word's fail me.. 1thud1

hot ford coupe
08-05-09, 02:18 PM
yu-rck/~\picpic Me too.

sydeem
08-05-09, 03:18 PM
Between the machinist, dentist and jewelers - I am spending all my time looking at their work instead of modeling.

DaveSohlstrom
08-21-12, 10:51 PM
gbritnell

Have you finished this engine and is there any more information about the engine. I would like to look into the possability of building a pair of engines for a big RC model Tow boat.

Dave

gbritnell
09-10-12, 08:18 PM
Yes the engine is finished. It can be seen running in the following link.
gbritnell
http://youtu.be/5QM-SBzFv9c
Have you finished this engine and is there any more information about the engine. I would like to look into the possability of building a pair of engines for a big RC model Tow boat.

Dave[/QUOTE]