Author Topic: Little Otto  (Read 1556 times)

Offline Alyn Foundry

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Re: Little Otto
« Reply #30 on: June 26, 2022, 04:18:05 PM »
It seems we were posting together Jason, I look forward to seeing the latest from the Blacksmiths department….
 ;)

I decided to try a needle roller bearing in place of the flanged Oilite bush the friction reduction is tremendous. From this….


To this….


The new bearing does nothing for the high precision machined flywheel so a new, replacement crankshaft will have to be made to accommodate some “ proper “ ball races.

 :cheers: Graham.

Offline Zephyrin

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Re: Little Otto
« Reply #31 on: June 27, 2022, 08:33:30 AM »
great improvements, your engine is now a runner...
I wonder why do you are using such a sooty flame and not a hotter one ?


Offline Alyn Foundry

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Re: Little Otto
« Reply #32 on: June 27, 2022, 01:24:09 PM »
great improvements, your engine is now a runner...
I wonder why do you are using such a sooty flame and not a hotter one ?

Hi Zephyrin.

Yes we’re definitely getting there. I have always found that the “ dirty “ flame seems to work for this type of engine really well, particularly on just finished engines.

Otto’s patent shows an automated flame delivery system that should mix the gas and air more effectively and, hopefully make a much cleaner burn.

 :cheers: Graham.

Offline Jasonb

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Re: Little Otto
« Reply #33 on: June 27, 2022, 08:33:05 PM »
A cast iron disc is supplied for the cylinder head or end cover - not sure what to class it as. No chucking piece on this but not a problem, after cleaning off a few bits of flash with the linisher it was held in the soft jaws, faced, OD turned and then a spigot formed to locate into the cylinder bore. After that it was just flipped over and the other side faced off but left over thickness for now.



I took a few clean up cuts off the inlet and exhaust blocks to get an idea of their final size and juggled them about on the engine to see what was the optimum position.





Once happy with the positions the some measurements were taken and then added to the CAD model. This was then used to complete the machining. From the underside there is a slot that lines up with the cast in slot of the inlet block that has had a chamfer milled on the inner edge to aid flame flow. The large circular hole is the exhaust, I wanted to get this as large as possible so have overlapped the flange but there is still plenty of metal around it to get a good seal. There are four 3mm holes to mount the inlet Block two counterbored and two others countersunk as the metal above the flange would be too thin to counterbore. Finally five 3.5mm holes for the studs to hold the part to the cylinder, the the right two will also hold the exhaust block.





After drilling the two stud holes in the exhaust block these were used to set it level in the mill vice so that the exhuast pipe boss could be drilled and tapped, as I'm making my engine to metric sizes I opted for M10 x 1.



This thread was then used to hold the casting in the lathe so the boss could be turned round and then blended into the main shape by hand.



My mill has no problem doing circular recesses so I cut a 20mm dia x 11mm deep one first then a 10mm x 1mm deep one in the bottom of that. The 20mm dia will locate the exhaust valve disc and the smaller one the spring. I then needed a way to allow the exhaust gasses past the disc so milled four pockets just leaving a small sections of the 20mm dia remaining.



Quick check with a  piece of 20mm bar and it just fits nicely







Offline Alyn Foundry

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Re: Little Otto
« Reply #34 on: June 28, 2022, 12:17:17 PM »
As mentioned in other places, I really liked the way you provided the exhaust valve guide Jason.   :ThumbsUp:

We definitely have different ways and ideas of how to make this engine. I opted for rather small, for me, stainless Steel 2 mm studding to hold down the valve block to the cylinder head. And also used 2 mm Brass grub screws as a guide for the exhaust valve disc.

I used a tee slot cutter to create the slide ways and more 2 mm Brass grub screws to provide adjustment. The photo says it all….

 :cheers: Graham.

Offline Alyn Foundry

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Re: Little Otto
« Reply #35 on: June 28, 2022, 01:20:46 PM »
I must add that my engine was rather hurriedly done with a view to it joining its big brother over in Holland earlier this month. I went for as many “ off the shelf “ components that I could to save on machining and fitting time. I used 4 mm Rose joints for the conrod and Oilite bushes for the mains. This has now proved to be a problem insofar as the conrod is really noisy and the bushes are really heavy on friction.


 :cheers: Graham.
« Last Edit: June 28, 2022, 01:23:50 PM by Alyn Foundry »

Offline Alyn Foundry

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Re: Little Otto
« Reply #36 on: June 28, 2022, 06:27:40 PM »
Today it’s hard to imagine that these engines were in common use driving small loads and were built in reasonable quantities. Here in the UK a patent was granted to a Mr R M Lowne in 1892 for one such engine. He manufactured is own versions, a picture of a twin is shown below. Another firm, Hardy and Padmore, also made a vertical version under license.

What’s interesting to note is that they both used Brass pistons. So armed with this knowledge I decided to try out a different approach with Little Otto. I have had quite a bit of experience with metal spinning over the years making spares for Tilley lamps. There’s virtually no waste involved with the production and the finished product requires very little work to complete. A Steel “ chuck “ was turned up with the ubiquitous 1” Whitworth thread made to fit the spindle nose of the spinning lathe. Discs of 2 mm thickness “ cartridge Brass “ were then placed upon the chuck and spun down to form a cup. The first attempt saw a taper of over 2 mm from crown to skirt, absolutely useless…. The chuck was gently tapered down from the crown to the skirt end, the cups were then re annealed and the metal sprang back to under the permitted maximum diameter.

The Brass piston spinning was then placed upon a suitable mandrel and the OD machined parallel to suit the cylinder bore. A single stainless Steel counter sunk Allen cap screw was used to fix the piston to the small end yoke.

Photo 1. The chuck.
Photo 2. Lowne twin cylinder.
Photo 3. Hardy Padmore engine.

Offline Jasonb

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Re: Little Otto
« Reply #37 on: June 28, 2022, 06:46:31 PM »
interesting little engines.

As Grahams piston is now in the engine here is mine as it came off the spinning lathe, just a few thou of taper due to spring back, it's a fine line between getting a parallel side and not being able to remove the spinning from the former, no doubt mass produced items have the time to do a few more test ones to reduce the taper to a minimum.

Was it 2mm sheet or 1.5 as that is about what the flat part of mine measures, bit thicker around the edge as you would expect.


Offline Craig DeShong

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Re: Little Otto
« Reply #38 on: June 28, 2022, 08:33:31 PM »
Jason and Graham, I’m enjoying watching these builds and the two different approaches you are taking in this fascinating engine.
Craig
The destination motivates us toward excellence, the journey entertains us, and along the way we meet so many interesting people.