Due to my absolute hatred of set screws on shafts, I also did the flywheel with my version of a taper lock bushing.
Another Stuart Twin Launch build started.
- Thread starter David Shealey
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I had wondered how I was going to control the air into the engine, thought of several options, decided to design my own input manifold with valve incorporated. I used o-rings to seal the copper line between cylinders.
I posted a short video of the engine running! It ran great right out of the gate!
Hi David, It certainly manages the quick changes of gear! Do you plan a boiler and boat? - or is life easy enough (!) just making engines??
A great job. well finished and sounds sweet - with no clattering! Proof of the care you have taken.
Well done!
K2
A great job. well finished and sounds sweet - with no clattering! Proof of the care you have taken.
Well done!
K2
THANKS!
I did this in memory of my dad, who got the kit from his coworkers at retirement. Unfortunately he only got the base plate done before he passed in 1984. After my mom passed, we cleaned everything out to sell the house, and I got the kit, and a few years later decided to finish it. I have no plans to build a boiler. One of my hobbies is machining, since I did that for a few years before going back to school and becoming a machine design engineer, which I did for over 40 years. I built up a pretty nice shop in my basement, and have really enjoyed getting back to the early days, except better now with the nice DRO's which were not around in my tool and die maker days. It has been fun figuring out how to do pretty complex shapes without CNC!
All the reversing mechanism parts are aluminum bronze and 303 stainless steel
I did the valve timing as close as I could by eye during assembly, surprised how nicely that worked! In the CAD layout I did, saw how the timing looked, and increased the size of the valve slider from the drawing size of 0,562 to 0.600, thinking I could narrow it as needed. Looks like no changes needed! Actually A little larger would have worked even better. At VERY low speed it will lock up in one direction, but not the other. I think the clanging some get is the valve opening too soon before TDC/BDC, which my increased valve size overcame. I read that with steam early opening is better, but since this one will never see steam glad I did the oversized valve.
All those years of machining and designing lead me to build this with close tolerances. All the bearings are 0.001-0.0015 clearance, so no bearing noise. Before putting the rings and gland packings in I could spin the engine with two fingers on the shaft!
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You have done something to make your Dad proud! Run it often and think of him and what you did together. This engine is one of those.
My mate is an ex-toolmaker and abhors my "lack" of precision. So I appreciate what you have done - beyond my skill.
Well done!
K2
My mate is an ex-toolmaker and abhors my "lack" of precision. So I appreciate what you have done - beyond my skill.
Well done!
K2
Thank you!
grahamgollar
Well-Known Member
I was interested in your personalised taper lock bush. I was recently machining a 3 throw crankshaft from 1.75" solid instead of the 'Lego' kit construction suggested by the drawings. I left an oversize flange at the flywheel end but needed a similar flange on the free end for locating the centres of the crankpins during the offset machining (I know - I should have left a flange on that end as well, too late!)
Anyway, I discovered a supply of miniature taper lock bushes which are available down to 1/4" dia and fit into a parallel bore. They only cost peanuts so it wasn't worth the bother of making my own design. They go by the name of Translock, grip really securely and are available in Imperial and Metric ranges. I guess you older hands know of these but, despite using very large Taperlocks in years gone by, I had never realised that there were miniatures available.
Attachments
I have used Fenner Drive bushings, along with Misumi, Ringfeder, and others in my decades of machine design. I had looked at the Trantorque Micro from Fenner, but the OD and length was too large to fit easily into this small flywheel, so I made my own. The Trantorque micro was about $20, my home made one was fab time only. 8>)
David, thanks for sharing with us, that is one good looking engine, great workmanship and runs great, you have to be proud of that one, thanks again, Joe
Thank you Joe! It was a really good exercise in design modification, fixturing, and machining. Kept me off the street for a LOT of hours. 8>)
Richard Hed
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When I was a very small kid (last week), my Dad poured and scraped some babbits. I asked what he was doing and he told me. But in all my life, that is the only time I ever saw anyone doing it. I have since wondered what the exact composition of babbit is. Does anyone know?
Richard Hed
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you got that right about "shocking" Stuart drawings. I have to admit, I wasn't "schocked", I was PISST! Frankly I thot these drawings were unbelievable. It would take so little effort to correct them yet it is not done.
On Babbits... my Stuart Sun engine had a bit of wear on the big-ends. So I tinned them with a "lead-wipe" of electrical solder... perfect! A couple of thou of solder took up the slack and left a tin-lead surface.
K2
K2
There are several grades of Babbit. Most common ones consist of Tin, Lead, Copper, and Antimony.
https://en.wikipedia.org/wiki/Babbitt_(alloy)
When I worked for a local Car manufacturer, on crank bearings, we took Glacier metals which were an Aluminium - Tin Alloy for a "lower performance" Cast Iron crankshaft engine. The Glacier specialist and my Company's Doctor of Tribology were discussing how much silicon was in the alloy, which they claimed "polished" the cast-iron crank by a burnishing process. The alloy was cast onto the steel backing - just like Babbit - rolled and pressed, clipped to size, set in pairs and broached to size. (I remember setting bolted-up half bearings in the 4-jaw in the lathe as an apprentice, and boring the Babbit to a thou tolerance. I can't remember the detail...). As the process was not as capable as the engine design required, they were all measured (automatically) and graded, then we built the appropriate grades of bearing against the Housing and journal dimensions. This was the way to ensure the correct clearance to within a few micron tolerance. A factor of 10 or more times better than we can achieve in our home workshops!
Of course, higher performance engines, with forged crankshafts, used phosphor bronze shells which had expensive anti-corrosion metal plating (A couple of microns of Indium? Niobium? - I can't remember...). Who has seen corrosion on their model Phos-bronze bearings? Probably no-one, as we mostly don't run pressurised oil in model engine bearings... so we see wear marks. But full-sized engines for thousands of hours use need these levels of technology.
K2
Of course, higher performance engines, with forged crankshafts, used phosphor bronze shells which had expensive anti-corrosion metal plating (A couple of microns of Indium? Niobium? - I can't remember...). Who has seen corrosion on their model Phos-bronze bearings? Probably no-one, as we mostly don't run pressurised oil in model engine bearings... so we see wear marks. But full-sized engines for thousands of hours use need these levels of technology.
K2
Not only are the parts poorly dimensioned, some wrong, some missing dimensions, and NO tolerances given, but there is no assembly drawing. For some reason the parts have numbers in the corner, as if they are going to be referred to, but the assembly drawing has no references, and is missing detail. Glad I spent years on a drawing board, and many years on CAD designing machinery, was able to figure it out relatively easily. I imagine someone without a lot of experience having a very hard time making anything precise.
My experience with the 1963 drawings of the Sun engine were much the same. But I could easily rectify the errors. I understand your frustration about them being wrong. Bad business from Stuart I reckon. How about castings? Mine were all good.
K2
K2
James Barker
Well-Known Member
David, I REALLY like the design changes you made to the eccentric as well as the reversing lever. I am wondering how much vibration that clamping arrangement will make with the engine running. Of course steps could be taken to balance that out. Well done.
BC1
Jim
BC1
Jim
On Taper-locking parts to shafts: On small shafts I use simple Olives (double taper sleeves) with a nut over the whole that screws onto the boss of the flywheel. Sometimes proprietary plumbing fittings, sometimes my own made parts. On a recent build of a double Sturmey-Archer generator, the central holder to hold the the outer magnets is clamped to the shaft that way. Most wheel bosses (e.g. on a toothed-belt drive I have in a boat) have a suitable boss to thread for the nut, and a small countersink acts as the taper on the part. If you need the olive to easily come off, I suggest using an O-ring, as the friction is adequate for most model applications where I have done this. It does not look "authentic original", but is a very simple way to secure flywheels and pulleys to shafts on many models.
K2
K2
