911hillclimber

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.

A bit more of a tease doing the crank shaft this afternoon. The crank is not co-operating at all. Slowly machined the shaft down to 5/16" ish using the tipped side n face cutter, new for the hacking down stage, then a fresh tip to get to a size that gave a nice running fit in the reamed bushes. That sounds easy, but was a sod to do, but now have a crank that fits into the case. However.... The pin that I just about managed to save and now 6 mm dia is in the wrong place. The throw is too large. I have obviously set the 7/16" throw to far or have crank case diameters too small or both. The clearance from the pin to the rear cover thread to far too small. Will measure tomorrow, but on the face of it would demand a big end con rod wall thickness of a mere 1/13", it should be 1/16". So, what to do to fix this? My thoughts are to remover the machined pin, and drill for an oversized pin, braze it in and machine the pin to a stroke less than 7/16", more 3/8". At this stage i have nothing to loose but to try it all and see if I can get it work. IRRITATING.

Thank you Dave, just the kind of post I expect on this great forum which I've used a LOT to get me over my model flying pains! There is a spark ignition engine on Hemmingways which I really fancy next.... Hemmingways are only 20 mins from me so can get another bar of En8 from them and do the crank again to drawing, but would braze an 8mm fresh pin in first and machine the over sized pin to 1/4" dia first. But this one first. Back from a nice sunny drive/visit to Ludlow today and some safety glasses i can actually see through. Seems I need them. (LOL)

Every day is a school day! The tool dug in as I was cleaning out the radius of the pin to the crank web trying to get the rad to = the tool tip rad. It is not too bad, a big end 6 mm v 0.25". I wonder about removing the machined pin and drilling/ream a 5/16 hole and make an En8 pin to fit and braze it all then set=up and machine the inserted pin to 1/4", but a lot of messing about. I'll need a 6 mm reamer now if I stick with it. In hindsight, I should have machined the blank down to around 5/8" and put that in the Vee block which would have tucked the two jaws in tighter, but we are where we are! I plan to machine the crank to 5/16 to suit the bushed reamed to that size, An hour should have that done. The lathe on it's lowest speed and the tipped tool machines badly. An old lathe but all I have! Feeling a bit dispondant at the moment, but tomorrow is another day.

Had a hard few hours in the garage on the crankshaft where I sort of managed to dodge a bullet. First, surface finish and tools. Tried a new tip, cuts well for 4 passes on En8 and feels dull after but still cutting. Tried HSS on the same material, no difference just so hard to shape the tip on a small grinder. With a good tool form results may have been better (?) Raised the lathe spindle speed to roughly 2 x the normal speed. Cutting much better using a fresh tip, but the belts are too tight and the head stock bearings were getting hot! Back to normal speed and light touch. As to the bloody crankshaft pin... All was going well right down to about 10 thou over the 1/4" pin diameter and suddenly the tool dug in, stalled the lathe and put a deep gouge in the pin AND rotated the bar in the chuck so loosing the pin position, just about the worst thing that could happen at this stage. Got the pin roughly back into place, but the pin still eccentric no matter what I did, so with it around and about right decided to carry on turning the pin until it cleaned up. This was, of course, below 1/4" dia BUT smack-on 6 mm so the con rod will have a big end dia of 6 mm and not 1/4" and we shall see what happens. Crank now back in the 3 jaw and busy machining down to 5/15" dia, lots of swarf. Day off tomorrow which may be just as well! 73T 911

Found the Hemmingway design on the web page, nice approach. The cuts I use are by instinct, 1/4 turn to 1/2 turn seems to be about 10 thou and I can cut 2 to 3 " in about 10 to 15 seconds all by hand turning the center screw on the round bed. I have a dodgy digital caliper to use to see how i'm progressing and down to the final pass. All a bit by touch and sound! Oddly, there is a graduated dial under the cross slide to set the angle od a taper cut, but you need a torch to read it. That is the only graduated control.

Well said. My daughter, who is approaching 38 now did Resistant Materials, an amalgam of metal and wood work. She took to it well but when things broke at her local school they stayed broken, never fixed, so the practical side disappeared quickly. She now works in property and is restoring a house with her husband who has trained her in nail gun use to polyfiller... Hope it warms up today so I can get back on the crank this afternoon in the garage, flippin' cold out there!

Interesting! Know the belt type you describe Jeff, thank you. Going to try machining with HSS tip tomorrow, see if that is better. If I speed the lathe up i loose torque and then the cut has to be even lighter. All this 'compromise' comes to play when cutting large diameters, around 1" or above the old lathe gets marginal. Come down to 3/4 or 1/2" max dia and all is far better. Still love this old lathe and these little challenges .

No idea at all. It is limited to a few pulley sizes and the V belt can't be adjusted to all of those, so the speed I'm using is 'one speed fits all'. I think is is part of the issue of surface finish and depth of cut. The motor on the lathe is not the strongest...

Thank you Brian, kind of you to say. This project has been interesting for me beyond what i expected. I think the Vees and clamp were indeed EITB as I made a marking out stand too, and a machinists vice, a Vee screw jack, a hacksaw, an adjustable pipe wrench and a tool box to put the lot in. Also made a small vertical drill press (!) but the thing got stolen at the end of the year. The Apprentice School closed after my year moved out.... No idea how i made all that lot. The plan is to machine the 'centre' off on the pin area and then centre drill off the tailstock and have a dead centre engaged. Pulled the tail stock back for ease of use and to calm my nerves! (and to take the pics) Tricky to get the tool bit right up to the rod pin as the tool holder is a bit balky.