911hillclimber

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.

With the crank done, it was time for the connecting rod. It is to be machined from what feels like En1, but cut well. The critical dimensions are the centers of the pins and the radii of the big and little ends. Simple. And so it was! The compound slide made easy work of the critical holes, all reamed out and a very nice snug fit to the pins. Time then to fit the crank and be sure it is free to spin, the rod to the crank pin and finally the whole lot articulating correctly. The last bit was a problem. The drg shows two relief cuts for the rod, but mine were nowhere near open enough to allow the lot to rotate so a few hours with the dremmel and a carbide tip ground the inside of the casting to clear the rod. Possibly, if i had removed more metal off the shank of the rod less would have had to be removed, but all done now and it is free to spin or rather turn. The back cover fitted and tightened gives the crank end float of about 4 thou, 0.1mm which feels about right (?). For something totally different i think I'll tackle the carb and tubes and needles fuel bowl etc next before lapping the cylinder and making the piston. L o n g way still to go. Can't help thinking I'm making this engine in the wrong sequence. Some pics as ever: 73T 911 C

Thank you Keith. The con rod machining went really well this afternoon, all drilled and reamed and both ends radius'd with a pillar file and a machined former as a guide. Will complete the taper tomorrow. Sometimes hand tools are faster than machining. Hope to have a go at the piston tomorrow too.

At long last the crankshaft is finished, it fits, and it goes round with no radial play and 0.25mm end float. Nice to use metric! This is the completion of the bottom end and time to fight the con rod. It is a fight due to the lathe and my accuracy, nothing hard, just fine machining and for a lathe that has had a big chunk of the cast iron cross slide knocked out of it, it has led a hard life in the past. It has it's limits! You can see the missing bit in the pic below. It seems to me to be very hard to find the centers on these smaller pieces, and heaven knows how I will get the small end pin square through the iron piston. Never ever machined cast iron before, but what can go wrong? Anyway, a few pics as ever. Funeral and MoT tomorrow, but hope to get a good Thursday on the rod. 73T 911 Coupe,

Thank you Dave for the ideas. However, I've avoided the tapers and have modified the prop drive to a simple step in the shaft and it will be a shrink fit when the crank is finally installed. Very simple turning in alum and a sleeve prop nut that will have an OD to match the large prop for this engine. Those details are in the near future. The next task is cutting the crank web 'scalloped' to remove the weight and to balance as much out as possible, but taking not that a true balance cannot be achieved. I'm following that detail on the modelenginenews Sparey build thread. Hectic few days recently, so progress has nearly stopped, but hope to get going again soon.

Must admit I am trying to avoid the faf of thread cutting! Over the years i have collected a few old engines, all spark ignition and the last one was only £18 with a great fuel tank (diesel though) with a neat filler cap etc. One like that off a dead engine would be perfect.

I have thought about a fuel filter cartridge as the basis for the clear tank, but not sure is araldite is fuel proof.

I doubt anything I've restored mechanically has not been modified! lol The lathe can machine a nice external taper, it is the only function on the Drummond that has a 'gauge' on it, but it is cutting the small long similat taper that gets tricky. The induction inlet 'bell mouth' was tricky enough and that is massive in comparison. I was thinking to machine the prop end of the crank to 6mm dia. This will give a shoulder against which the prop flange can locate. The prop itself at 12 to 16" dia (!) has a hub dia of 8 mm i think, so a prop hub with a 6mm hole and an 8mm dia and then threaded M6 to take the prop 'nut'. Shaping the crank web will be awkward, but i will cut the side scallops out by hand roughly and then mill to true things up using the compound slide. That will be the next job, possibly tomorrow pm if I'm home in time. There is a gap between the crank case and the screw-in rear cover which i left a bit long, so that needs machining down to allow the cover to be tightened andd still give some crank pi clearance. I guess that clearance only needs to be about 1/64" or a 1/32". You could call this crankshaft float. As to borrowing parts from other engines, I am looking for a spare fuel bowl instead of the design's aluminium tank. A nice clear one say. You can buy new Mills 0.75 tanks but they must be minute.

I’m open to all ideas!

Thank you Keith. The crank has some more work needed yet, the shaping of the web as you say and the prop drive hub. I'm not cutting a taper as the design but using a stepped hub in ally. I can't machine male/female tapers on this lathe! While the pins were arriving i have adapted a home made face plate that came with the lathe to me and have made an adaption of my Vee block. Will detail when I've skimmed the mounting surface clean and added some paint.

Con rod pins came a day early, so got one in the crank after 'just' reaming the hole 1/4". The pin was a force fit, not a very high interference, but a good tight one. Didn't use loctite as i forgot! Thus, i think this crank pin saga is at an end. Collected my new En8 blank yesterday from Hemmingways, so all set nearly to make another (if I fancy to) Social weekend now as my motorsport interests kick-in, so back on the engine next week (dreaded con rod) 73T 911

Thank you for this detail. Not sure if I want to do another! Good to see though, just might make one when done.

Spent a few hours fixing this bloody crankshaft. I've ordered some ground 1/4" pins 3/8" long, so right dia for the con rod big end and right length. Bought 4 for a £5, hope they come soon. I've removed the machined crank pin and drilled the crank web to the right stroke and drilled under the 1/4" reamer size, so best drill I had is a 6mm Dormer new one. Set the crank in the lathe, removed the pin. Set the new/correct centre for the pin and drilled it 6mm dia ready to be reamed. Did this on the compound slide head which worked a treat. Advice is to ream the hole 'just' so the dowl pin will 'just' enter the hole. The reamer has a very very slight taper to the nose to ease the reamed dia to be made. Remove the crank and squeeeeze the pin in, thus an interference fit. Need those pins! As advised, the 4 jaw chuck has been damaged by my clumbsey mishaps, Jeff was right. However, managed to strip it down and after some swiss filing to 3 jaw screws all is working like new. My Vee blocks are going back into storage... I feel like I'm dodging bullets at the moment. Every day I lean something. If I make another crankshaft I will turn the blank to shaft dia for the bushes and turn the crank web to thickness. All 3 jaw stuff. Transfer the machined blank to the cross slide. Pick-up the crank centre to the chuck and then index the stroke on the compound VERTICAL slide as it is fitted with a dial. Drill and 'pin-fit ream' as advised. That would be SO much easier! 73T 911 Coupe, road/hillclimber 3.2L

This is very useful real-life experience, thank you all. Just been to Hemmingways for a fresh steel billet, but now home it is too short! Thus, a short ish return tomorrow i hope to swap for the right length. This is an insurance incase the pinning idea fails... I will try the force fit. I have borrowed a 1/4" reamer from my oldest friend (who has now joined this forum to keep abreast of my adventure) so that should fix it. I'll order a ground pin as suggested before from Simply Bearings. That should negate the need to machine the pin I hope. These things are sent to try me!! Mind you, I doubt a Myford Super 7 would help.lol

That approach had gone through my mind too, but I'm not sure I can get the pin in square to the crank or indeed to get the right interference fit to get the pin in tight and for it to tolerate the engine running. This is why I had the thought of En8 pin oversize and brazed in (after press fit). Machining the pin as before will get it square as the dia is machined down to a 1/4". If I allow the parts to air cool slowly the En8 should stay reasonably soft.