Hubbard Marine Engine

[deverett]

Thanks for that table, John. It will come in handy for the future.
JB. I know about high revving engines using plain ali bearings but with my machining skills, or rather lack of them, I would prefer to use more 'conventional', if somewhat dated practice. Besides if the engine ever gets THAT much running and the bushes wear, it is much easier to slip in a new bush than having to rebore the con rod and bush it anyway.

Dave
The Emerald Isle

 

[deverett]

Just a small update, but no pictures - there's not much to see.

The liner uses Loctite 574 as a gasket medium to seal the various gaps between it and the cylinder casting. With the shape of the bottle, it was easier to squeeze some onto a coffee stirrer and wipe it on the required surfaces in the casting. To make sure I got 'sufficient' to make a seal, I spread some on the liner as well. Slid the liner into the casting and gave a slight twist to spread the compound and line everything up.

It was then just a matter of wiping away the excess sealant with an acetone soaked rag. Afterwards, temporarily sealing the various orifices except one, I blew through to make sure the the transfer passage was clear and that the cooling water passage was clear.

Dave
The Emerald Isle

 

[deverett]

The preserved engine at Mystic Seaport has a simple wooden stand. This was copied for my model for when it will be finally mounted on a display board.


Next on the agenda is a fuel tank. Old boat engines would probably have used a cylindrical tank, so a handy offcut piece of 7/8" diameter copper plumbing pipe was utilised. 2 nipples were made up - one for the filler and one for the feed pipe and silver soldered in place. 2 pieces of copper plate became the ends. These were stuck to a superglue chuck and a thin cut taken to provide a locating spigot.


After silver soldering the ends, the tank was cleaned up, ready for mounting.


The fuel level has to be above the fuel needle in the carburettor so a base was made up from some plywood - I didn't have any suitable solid wood. To make the cutouts the plywood was sandwiched between two other pieces of scrap wood and a hole saw put through the lot. I made sure that the pilot drill was lined up with one of the tee slots in case I went too deep.


The plywood was then sawn in half for the two pieces giving nice half round recesses to hold the tank.
Some brass banding was used to hold the tank to the stand. I wish I had made the tank a bit longer, but I didn't want it to appear too large alongside the engine.


One of the things I didn't do earlier was to put the balancing holes in the flywheel. This was partly because I didn't want to see a series of holes in the flywheel. I had a flash of inspiration and so the flywheel had the required balancing holes put in and these were hidden by a fitted piece of ally drink can cut and glued in place and smoothed off.




Dave
The Emerald Isle

 

[deverett]

And for a change, a few external fittings.

The cylinder oiler was made to the words and music from Morrison & Marvin's 1/4 scale oiler, but sized slightly differently and shaped for this engine. The glass tube was a convenient size cut from a piece of test tube. The elbow started out as one of a street ell casting tree from PM Research. The smallest size was still too large, so plenty of filing was needed to get it to an acceptable size.

The machining jig has been described on this forum before. The design will hold any of the PMR cast fittings of one size.

Inspiration for the priming cup and crankcase drain was drawn from a Stuart cylinder draincock.
I used the same form tool used on the pump check valves to form the spherical parts. A piece of brass hex was chucked and roughed out. Then the form tool came into play to shape the body.


A hexagon was filed at the top of the stem.
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The cross hole for the handle was drilled and taper reamed for the handle. I did as much work with the part still attached to the parent stock for ease of holding.


The body was then parted from the stock and the threaded stem was held in a mandrel so the cup could be formed.

I could not bend the cock handle either cold or hot. At just over 1/16” diameter, the barrel kept breaking off. In the end, I turned the barrel and made a larger boss and silver soldered a handle to it and then filed it down to a reasonable representation of the full size.

Next was drilling the cross hole for the retaining split pin. The simple jig is just a piece of square steel stood vertically in the vice and a hole drilled for the bore of the barrel. It was then turned horizontal and the cross hole drilled through. This ensures the two holes are on the same line. Slide the barrel into the long hole and there you have your cross hole. Just the taper where the barrel goes through the body to machine now.


And this is how they ended up, the cylinder oiler crept into the picture, also.


Dave
The Emerald Isle

 

[deverett]

I have just got home from attending the Bristol model engineering show, where I'd agreed to show this engine. Mild panic had been setting in recently as I tried to get the engine finished before I set off to England. I realised a while ago that I would not be able to complete it beforehand, so the engine was temporarily assembled as far as I have got with it and a mounting board was hastily made up to put the engine and sundry bits on, and I took it unfinished to fill a space on my stand.


With family commitments and another local show, it could be a while before I get back to the workshop.


Dave
The Emerald Isle

 

[Cogsy]

it could be a while before I get back to the workshop.

Is 'a while' up yet? Looking forward to seeing more of this one...

 

[deverett]

Indeed it is more than 'a while' since working on this engine.

I could not get it to run. There must be a mistake somewhere in my measurements, but I can't find out where. The fact that the piston does not completely open the exhaust port would suggest either the con-rod is too long or the piston is too tall/gudgeon pin in wrong place, but all look OK to me.

I have got as far as making a new slightly shorter con-rod and will make a new piston, this time in ally, moving the gudgeon pin higher. The upcoming problem with these changes will be loss of compression ratio. The only thing I can think of to combat that is to make a new cylinder head with deeper spigot in the bore.

My attention span on a project seems to be very small especially if things don't go right first time, so it has been put on one side while I to try and finish off some of the other dozen or so part made projects.

Dave
The Emerald Isle

 

[deverett]

Over the past few weeks, I have returned to the Hubbard trying to get it to run. All I can get are a few pops - nothing more.
I've got good compression, there don't appear to be any air leaks into the crankcase. I've tried flooding the cylinder and turning the engine over until the excess fuel is exhausted. I don't know what to do now, except paint it and call it a Static Exhibit.






Next project will definitely not have any 10 and 12 BA threads into soft, gummy aluminium.

Dave
The Emerald Isle

 

[natalefr]

Awesome !
Do you have video about your fabulous engine ?

 

[minh-thanh]

WOW ...It is so cool !!!!!!!!!

 

[deverett]

Awesome !
Do you have video about your fabulous engine ?

'Fraid not - Like I said, I can't get it to run so it is a Static Exhibit

Dave
The Emerald Isle

 

[rac37]

Very nice! I had the same problem with mine, could not get it to run more than a 15 seconds. Anyway I converted it to a 4 stroke design and she really runs nice.
What was a winter project turned into a couple year ordeal, but was really fun to figure out.

Bob