A tiny 3 Cylinder Holt based engine

[fumopuc]

Hi Georg, thanks for the up date. Good luck for the next attempt.

[gbritnell]

Now that the engine runs I'm moving on to the radiator. I didn't want to make any more than I had to until I got it running, water pump, brackets, radiator etc.
The radiator is being built by the same construction method as the larger Holt engine rad., fin tube cut from square brass stock, machined tanks and header plates and all soldered together with side plates.
The larger rad has the word HOLT machined onto it. I made up a step-off chart and cut the lettering with a .062 end mill. This one being 1/2 size I had reservations about doing the same job so with some knowledge of modern printing processes I created a model and sent it of to Shapeways to be cast in brass. They said about 2 weeks.
In the mean time I started on the fin tube. I took some .50 brass rod and cut 5 lengths to 2.40 inches long. I then through drilled the pieces to .120 diameter. The pieces were then milled to .312 x .375.
To hold them in the collet I turned up a length of aluminum rod then cut a slot .375 x .154 deep, .002 shy of half the .312 thickness. Two pieces were then cut from the rod and marked with a dot for assembly.
For the first cut the bar was projected out 1.20 and the .04 wide necking tool was touched off to the end. I then turned . 17 diameter for a length of .065. The fins are .018 thick and with the tool .04 wide this gave me progressive steps of .058. I marked all the numbers down on a piece of paper to follow.

[gbritnell]

I cut the first set of fins then pulled the bar out to 1.90, picked up the end of the bar, set -0- and then proceeded to cut more of the fins. I did each piece identically with the hope that when the fins were finished the would all match up.

[gbritnell]

At this point I marked the rod for registration then turned it around to finish the last .50. Using a magnifying glass I carefully picked up the last cut then stepped out to the end of the bar, cutting the same diameter as the other end. These will fit into the header plates and be soldered.
I lined up all five pieces to show that by doing each one exactly the same way produced very good results.
gbritnell

[b.lindsey]

Those look great George . Shame about the lead time from Shapeways, but will no doubt be worth it.

Bill

[ShopShoe]

gbritnell,

I follow and enjoy all your engine builds, but I have to add that the radiators you make are worthy of special mention.

You have got to be the godfather of model radiators.

Thank You for sharing your projects,

ShopShoe

[gldavison]

Hi George,
Your 3 cylinder radiator is another master piece. I would like to inquire why you milled the tube from .5 “ square, as opposed to just using square stock. Just curious about that. Also when you drill the end plates, will you space the holes exactly .375” apart, or will you allow a little more so as  not to have any interference between tubes?
Am thinking of making one for my Snow engine.  Working up a drawing Fusion.
.

[gbritnell]

Actually it was.50 round that I started with. That would let me get the.375 dimension. I didn't have any square stock on hand and I had a lot of the round available. With the price of brass seemingly just shy of gold I really don't want to buy any more than I have to.
I will leave a couple of thousands space between the tube centers just to make sure there is no interference.
gbritnell

[gbritnell]

Gentlemen,
I know it's been a long time since I posted anything on the tiny Holt or anything else for that matter. I've been extremely busy working on some engines for a fellow, a couple of Wall engines that are in dire need of refitting, to say the least.
Anyway here's an update on the radiator. I got the top tank back from Shapeways and I'm thoroughly pleased with it. I asked for raw brass (unpolished) but it looks like they went ahead and did some kind of smoothing and polishing. It wasn't the greatest job but it didn't take much to clean it up.
I machined the top and bottom header plates from a solid bar of brass. They are only .060 thick and have a .025 recess so I had reservations about trying to do it from a piece of 1/16th stock. I drilled the holes deep enough for the two plates then cut the recess in the first one. I then cut it free with a slitting saw. Same procedure for the second one.
The side plates had multiple steps so I started with a piece of 1/8th brass strip and and machined everything in one setup. When I unclamped the part it had warped a little but was easy enough to straighten out with a little coaxing.
I didn't know how I was going to hold everything together for soldering so I drilled and tapped one hole in each end of the side plates and headers. These were tapped .80 mm (.032 diameter)
Everything assemble quite nicely and once together I clamped a couple of pieces of flat steel strip across the the side plates to keep everything aligned for soldering.

[gbritnell]

I still have to drill the water opening in the top tank and drill and tap for the fill plug. The bottom tank will get a water outlet soldered into it.
gbritnell

[crueby]

That radiator is stunning!


 

[b.lindsey]

Thanks for the update George. The radiator looks fantastic. Good to hear the shapeways part worked out well too.

Bill

[gbritnell]

Gentlemen,
Happy New Year to all. The last time I posted was in the old years hence the greeting.
My last postings were of the radiator. I have has other jobs to do so I haven't really spent much time on the Tiny Holt until now. I kind of knew that the large flywheel in the front of the engine would pose a problem for the coolant line routing so after I started looking closer I decided to make a smaller flywheel for up front much like the larger Holt engine. I had a piece of 2.125 diameter iron so I came up with a design and using the rotary table drilled and carved out the smaller version. The nice thing about using iron is when you're using small burrs to do the shaping you don't get the tiny shards of metal like you do with steel.

[gbritnell]

Here's a couple more shots of the radiator prior to the finish drilling and tapping.

[gbritnell]

The water pump on the larger Holt is of the centrifugal type but I thought with this smaller size it might not move water properly so I went with a gear type pump. Having made numerous gears over the years I used one of the cutters to cut 2, 10 tooth, 48 pitch gears. The fit was very good, just a little snug at first assembly but with a little spinning with some very fine lapping compound they bedded in nicely. This will provide a tight seal at the tooth mesh for a better seal. The housing is proportionally similar to the larger engine and is mounted about the same, to the fuel tank bracket. The gear shafts and screws are stainless steel because of the water.