911hillclimber

Thanks as ever. You have more patience than me. I have nothing to loose, so will widen the rod swing slot in the piston. This may allow some float and allow the piston some freedom, or less binding. If I slacken the cylinder nuts off the cylinder the crank can be revolved much easier The prop arrived today too, it would fit a Tiger Moth….

Thanks for all the helpful details, but... Not a good day at the lathe today. Wasn't quite in the mood, but pressed on. Made a piston 'blank' that seemed a good fit in the cylinder, tight'ish at the TDc and slightly loose'ish at BDC. Drilled and reamed the wrist pin hole 3/16", no probs. Re-aligned the piston in the cross slide and started milling the inside of the blank to take the con rod. I happened to machine it 90 deg out, so no slot for con rod to articulate. Ok, turned the piston to allow correct slot position. Machined the 3/16" slot which sounded not quite right.... Removed the piston to find the cutter had gone throu the piston and was 1/16" off-set. Got my arithmetic wrong. God, I'm good at this stuff. Made another piston, all thou or so tighter (practice makes perfect), drilled holes, milled slots all in the right position. (practice makes perfect). Assembled the lot together and the movement is tight, cannot see any touching points of the con rod to the case to the cylinder etc so reversed the piston on the rod. Same condition, so something not square. I cannot see how to find and get rid of this high friction point, so seriously thinking of tarting the outside of this lump of metals, and put it on a stand. I finally think I'm a mechanic not a machinist. 73T 911 Co

Thank you Keith. The prop is in the post to give me a bit of incentive! Any thoughts on the fit of the contra piston?

The fine 1200 grit powder arrived 2 days early, so mixed some with a drop of engine oil and set to polishing the bore some more. I really doubt i can improve it further, so have called that a day, and started turning the cast iron piston. I'm experimenting of getting a good chatter-free cut as I reduce the bar, and may have found the happy spot of cut, feed, tool overhang and angle. Quite a few variables but will try some refinement tomorrow starting with a fresh tip. Plan is to make a new 'tight' fit piston by lunch tomorrow.

Great we all have a choice! This conversation is a direct parallel to the car industry, some will take EV and not. I'm sure the supply (as opposed to cost) of suitable fuels will govern what happens. If fuel stops then switch to electric and keep flying, enjoying all aspects of this hobby and all is well. IC vehicles will slowly die out, 20 years? The fuel for both will become the issue if/when electric becomes the best seller, the fuel will be the issue before the vehicles are worn out I suspect. Mind you, supply of electricity will also dominate the world too! We will all revert to rubber free flight....(just joking)

Just my take on this subject. I last flew/used IC when in short trousers almost and I cycled everywhere. I was 12, so about 1964. In 2020 I had retired early and fancied a return to model flight for some weekday action, preferably with vintage planes, ie Ben Buckle. However, what was all this RC malarky? I needed a trainer, so bought a foam Kingfisher with electric and all the gubbins needed and joined the local club. IC there is restricted to say the least, so electric was ideal, fly any day that allowed it weather-wise. Preparation very simple, charge the night before, go and learn to fly (not quite there yet). My 'buddy'/trainer flies a 4 stroke and it is really nice, love the sound, lover the performance (heavy plane cuts the air). However, cannot see me doing an IC ever, electric is just so convenient, bit lazy maybe, but I feel the right thing for me to restart the hobby. Is electric the future, I think it is, BUT, if you try a little, IC can be the way for ages. Fuel and noise will determine the way it travels, or rather glides, to the ground. I'll be long gone, but have memories of my new found hobby as electric, and a distant memory of my ENYA glow in my control line.

Dark grey, but imperfections in the bore. The bore was fine turned, don't have the right reamer, so tried to work the surface with a new boring tip etc. I have to wait for the 1200 powder to come a few miles from me, it is in Birmingham.

Lapped the cylinder using fine cutting compound I've used on car/bike valve seats, and what a difference that made! Changed the look of the surface, but removed a lot of the imperfections. Have ordered the 1200 powder for £6 off ebay. Thought I would try 'expanding' the piston by heating to cherry red and quench. Did that twice. The previously slack piston would now only enter the cylinder 1/2 way, so the growth was far greater than I expected. Started to mess about with the lower part of the piston as it was the tightest only to find 2 hair line cracks in the 'skirt', so now scrap. Further wait for the 1200 powder to arrive and then can progress I hope.

Thank you both. Birthday today is 'my day' so have to fix the brakes on my car trailer, the season is soon to start, then to focus on the lapping. Being old I have the double ended paste from various engine valve jobs done over the many years, so may go back and start again there. Between the fingers 40 feels like 1! I do have some fresh alum plate which is mirror smooth so can see how 40 scrubs the surface compared to 1. I can borrow a small US cleaner I've used for motorcycle carbs in the past to clean the cylinder after polishing, but like the idea of the 1200 powder and engine oil as the final pass. All part of this project!

Ok, I'll persevere! Is '1' coarse and 40 fine or the other way round for the lapping grease?

That was my stance too. Oddly I have a new PAW from the 80s so will have a peek. Maybe a new tight piston tomorrow on the agenda.

Some advice needed please. The selection of lapping greases arrived today from China in 6 days (!), all 20 of them... They are numbered from 40 to 1. All different colours. My first lap was with '20' and I've just tried a good dose of 10 but not sure if there is much difference in surface finish in the cylinder. The 40 feels like the 1 to my fingers, so which is the coarse one please? Less subtle is the bar of cast iron which also landed, so I'm keen to lap and then machine a new piston, contra piston, but need to lapp it all first. As to the surface finish, i would say it is good as it stands if i were looking at a good car engine bore.

Thanks, but no chance. Hemmingways are on holiday for Easter, so no cast iron from them soon, but have ordered a lump from ebay, but doubt that will arrive soon either. Will try the red heat and quench as I've nothing to loose, everything to gain. Pipped-at-the-post!

Thanks Keith, worth a try! While I wait for the fine lapping grease and some fresh cast iron for the piston thought I would do some boring bits. The needle itself has been made as my friend suggested, in the chuck and with a grind stone in the dremmel (and it at maximum rpm) shaped the needle point quite well. Turned a needle collar and soft soldered the needle and collar together with little fuss. All screws up and down with some nice resistance which I hope will resist the fine vibration of this turbine like engine... Next came the top of the cooling head and decided to add some more fins as the rest of the sleeve, more heart-stopping parting off tool work, what a din! Soaked the steel cylinder in citric acid solution, 20% crystals and had a good coat of bubbles on the cylinder after 10 mins. all rinsed and it looks much better, but still needs some swiss file work. Oddly, now ground to a halt, little else to do until the iron and grease turn up. Can this adventure (to me) actually be drawing to a close? Plan was to have it ready to run (really?) by my birthday, end of this month. Will i make it? Doubt it! 73T 911 Coup

Thank you for this valuable advice Dr. Trying to get in touch with Hemmingway today to get a bar of cast iron while I await the 1200 grade lapping grease to arrive. I have had a rod through the prop 'nut' as in the pics to turn the engine over repeatedly. Without the head on there is a light resistance as the piston is driven by hand up the bore, this could be a touch of binding due to the piston not being dead true to the various parts. This is with the cylinder tight to the case via the 4 nuts but no gasket between the case/cylinder. I think the piston is too slack in the cylinder, hence making a new one to match the honed bore. I made the piston really close to the un honed bore, my mistake. Same for the contra piston. Will try to make something to spread the C/P as an experiment and if it works will save me making one again!

Interesting! The piston top is by me and a pillar file... I watched a video of an engine (glow) being built the other day, and the builder pushed the piston and rod to the top of the cylinder and covered the top with his finger, sealing the head. A sharp pull down of the rod and the piston gave a loud 'pop' as it came out of the cylinder. The assembly was dry. Mind does that but not as loud and my piston was oiled. If I make a new piston I may as well machine a new counter piston and get it 'tight' in the head but after the fine lapping past has been used. I do not have a ball bearing anywhere near that diameter. When this is all done i will clean up cosmetically all the external surfaces to try to get it smart....

Chipping away at this project still, maybe 60% of the way there now. Finished the piston and it turned out oddly accurate, actually goes up and down the cylinder, BUT, maybe too slack. There is a lack of real compression, so I might make another to get it tighter. The contra piston is far too loose and follows the piston (oiled) down the cylinder on the down stroke. Sigh... I will need to get some more cast iron bar, maybe tomorrow from Hemmindways. Moving on, did some more to the 'carb' and with the arrival of a 4BA tap and die made the needle valve jet which screwed together well, and then the tank to follow. The tank was machined from the remains of the Alum bar i had over so is a bit small, but it only has to hold a small volume of diesel to prove it runs. It will never get into a plane. Lathe needs a bloody good clean, alum swarf everywhere, very irritating. Question, do I REALLY need a tight fitting piston? 73T 911 Coupe,

Jeff: Did you weld that up yourself? My back cover disc 'welded' itself too, but I quickly just about got it out before it gauled (?) tight. Crippled a lot of the cast thread. Great repair and rescue of the case, that casting is still a 1000% better looking than mine. The surface on mine is dog rough, a new pattern is needed at Hemmingway. How did you make the taper on the N/V please? A friend has suggested the piano wire in the 3 jaw and to grind the taper/point with a stone in a dremmel. Graham.

I thought even grey was the finish of it all! Bad news is I've turned the piston now, so it may be too loose when done, but easy enough to make a (second) one. I'll order some 1200 grease.

Bit frustrated now, so stopped, cleaned the bench and lathe and having a cup of tea. Needing to work smarter than harder. Two tasks done (almost) this afternoon. First task was to lap the steel cylinder to smooth out the rough finish which I thought was quite good, but... Made the honing bar from aluminium and tapped the ends M6, one for the chuck arbor and the other for the 'expanding screw'. Here, the trick is to drill and tap the adjusting tapping with a taper tap and use a screw to run into the taper and so expanding the bar, cut down the bar with a hacksaw. Works a treat. Bought some 320 lapping grease off ebay for a few ££ and ran the lathe and the cylinder holding the latter by hand. Slowly occillate to and fro to run the past along. 20 mins later got bored but also improved the finish. Pleased with that moved to making the piston and contra piston using the bar of cast iron supplied. Never ever machined cast iron before, felt and smelt very Victorian. That all wnt quite well until the milling of the con rod internal opening to allow full articulation of the rod on the wrist pin which drilled and reamed really well. The slot needed is 3/16" wide and all i had was a 1/8" slot drill and working sideways and almost blind (god, would love a small milling machine) the slot was anything but right. That's when i ordered a nice new 3/16" slot drill. This job needs stacks of small tools. 73T 911 Coupe

As a respite from steel, decided to make the 'carb' from the brass rods supplied. Machining the brass need some keen or new tools and the parts are quite fine and certainly awkward to make true and straight. Drilling some of the tube with a 1/16" dia drill for over 1" is a heart stopper at times, and near impossible to keep it straight over that length. Had to buy some 4 BA taps and die for part of the job, but this part has AF/BA/ISO threads all over it. The carb is made from 3 turned parts, two are silver soldered together, the third is essentially the jet which the 1/16" dia needle sits into, the lot fed from the tank I have yet to machine. Anyway, bar one thread it is all done, nut not my best work. I'm quickly realizing this fine machining is not my best skill...even if I had a new Myford! That lot to one side, started to make the lapping tool for the cylinder. The lapping grease now here. 73T 911 Co

1 Fabulous! even I can do that, will 'shamelessly steal' that. 2 I just do not know how to get parts and assembly to look that good. I need to try harder. 3 Sewing needle sounds a very good idea, will nick that too! Thank you for helping me along this road Keith.

That sounds hard! have the length of piano wire from the material kit for the needle valve…

I've done non of this type of work before Keith, so everything is new. I've built several Porsche flat 6 race engines and they are easier... I have dressed the rod as you describe earlier this afternoon, and used a sanding wheel in the Dremmel to fine smooth all surfaces, looks good! Never lapped a piston like this before, but will be following the Hemmingway method. The paste is a 400 grade, I presume that followed wet n dry numbers, so not too rough or smooth, but my choice could be wrong. I know i need to protect the lathe from the stuff and to have it running slowly. Made a good start on the induction brass works this afternoon, but running a 1.5mm drill down the one part for the needle was taxing as the drill i have is only just long enough to get just over 1/2 way down the tube, but the job is going well, the lathe is taking some very fine cuts off the brass with a fresh tip. The tubes cross over and the hole allowing the air in has to be drilled through several intersections and i fear snapping the drill, but we shall see. Have used some metric threads instead of the BA threads as i have no BA taps or dies, just metric and UNF.

Thank you Kieth. I refrained from 'detailing' the rod as I have no machining means to do an even balanced job on the features, but might trim the material between centers and not photgraph it as it won't be neat! Not sure what size prop to get, 16" x something or 14" x something. Any suggestions? 16" sounds truly massive to me. Awaiting the lapping grease, but can make the alum lapping 'arbor' (?), and work out the slowest speed I can get on the lathe. Not looking forward to that step. After this engine i was contemplating the other Hemmingway spark ign engine, the Atom Minor, but having watched the YouTube 6 part series on making it, looks far too complicated to make on my 'facilities'. I think this will be the first and last model engine build for me! I almost feel like making another of these now I've learnt quite a bit to have a good one.