Hemmingway 5cc diesel engine build?

[Dave Brooks]

I don't know if its any help or whether it will make any sense but I recently managed to turn a tapered collet and matching internal taper in a prop driver on the ML4. I used an end mill clamped in the toolpost as a boring bar. The end mill had the same diameter  as the small end of the internal taper and gives you necessary clearance all round. Taking things very slowly and in Aluminium this worked well. If you have a compound slide (which I think you do?) as long as you don't move it at any point between doing the external and internal tapers then they should match exactly. One benefit of the original tool post on the ML4 is the ability to clamp various different things and your Drummond is probably similar. To clamp the end mill I made a very simple, small aluminium 'v' block and the shimmed it and rotated the end mill to get one of the mill cutting flutes on centre. I did this with an 8mm end mill.

 

 

[911hillclimber]

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.

[911hillclimber]

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,

Edited March 12 by 911hillclimber

[KEITH BEAUMONT 1]

Machining cast iron does not give many problems. Especialy the bar supllied with the kit. Just make sure you get under the outer skin in one pass. The dust can be a problem, as it gets everywhere. If your Ways are oily I suggest wiping them dry, as a mixture of oil and CI dust is quite abrasive. I always put some kitchen paper over the area the swarf drops on.

Crankshaft is looking good.

Keith.

[911hillclimber]

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.

[911hillclimber]

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

[KEITH BEAUMONT 1]

Your problems withethe fitting of the conrod/crankcase have been made worse by not thinning the rod between the holes. like a "dog bone",but even then you would have found some unwanted contact, as I did, working to drawing dimesions.

Good luck with the lapping of the piston/cylinder.

.Before you go to the next part, I suggest you put a prop on and tighten the nut up to running tightness, to prove you still have a 4 thou gap.

Keith.

[911hillclimber]

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.

[KEITH BEAUMONT 1]

Just taking the edges off the rod part, with a file, folowed by a strip of emery cloth pulled and pulled  alternatley, wil give a nice finish.

What type of lapping grease are you waiting for?  The split lapp, as shown in the Hemmingway notes works well. Have you lapped a cylinder and piston before?

Keith

[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.

[KEITH BEAUMONT 1]

When I made the carb, using the method on the drawing of pre soldering the two parts. I did not drill the fuel tube, but used a piece of copper pipe of similar size. This saved the drilling problem.

400 grit is a bit harsh for final finish. Ok to start with that, with plenty of oil, I presume you have a reamed finish to the bore at the moment? Start with the cylinder first. The aim is to achieve about 1 to 1.5 thou taper, top being the small end. You need to get some 1200 grit powder for finishing Plenty available  on the net, You achieve the taper by "feel", concentrating more on the bottom end. Make yourself a plug gauge that just enters the top end,before you start lapping. You can then gauge how far you can enter the bottom end to check for the taper.Plenty of clean downs between each check. I use 3 jam jars, each half filled with white spirit and the part is washed in each one in turn. When you are satisf ied with the bore finish, start lapping the piston using same grade. The aim is to get the piston to stop at about top of the exhaust ports when pushed in by hand. This is the point where things can go wrong,as the urge is to think it is too tight. When all is really clean and you assemble piston into cylinder,less contra,put a prop on, 16inch x6 pitch is OK and try to gently turn it over with plenty of oil. It should feel tight about half way, but then wind back and forward, continually, with plenty of oil until you can just turn it over a TDC. When you achieve this, strip down , clean it all up again and re-assemble. You then fit the Contra and you are not far off hearing it sing! The contra needs to be a tight fit and I can advise on this if you wish.

Do you have a gramophone needle for the NV?

Keith.

Edited March 15 by KEITH BEAUMONT 1

[911hillclimber]

That sounds hard!

have the length of piano wire from the material kit for the needle valve…

[KEITH BEAUMONT 1]

Using a suitable size darning needle save a lot of time for the N/V.

I have recently finished a 5cc version of the 2.5cc Nalon Viper and the photos show the lapping tools used, The cylinder one has the adjusting thread cut with a taper tap so that screwing it in  expands the outer diameter. It is a good idea to put the screw in the chuck and file a slight taper on the leading threads. Slits are hand sawn.This one is held in the chuck and the cylinder is held in a gloved hand for lapping. The piston one is hand held,ditto and the piston on a stub mandrel is in the chuck.

[911hillclimber]

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.

[911hillclimber]

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

[KEITH BEAUMONT 1]

I am surprised that Hemmingway still do not supply a piece of 1/16" bore brass tube for that fuel pipe,to avoid drilling. You  did well to drill without it snatching and breaking the drill.   When you start to lapp the cylinder,take your time to get it right and with plenty of clean downs before final assembly,to ensure all the grit has been removed. I have the benifit of an ultrasonic cleaner and I am always amazed at the bits one finds in the liquid after use, although parts were really clean when put in the cleaner.

A compression ignition engine does not appreciate being stripped down after it has been run in.Just in case you ever need to do that make a mark on the front top of the piston, so you always know which way it fits. Also you need to machine or file the cylinder flanges to the same exact profile of the mating crankcase. This makes sure the cylinder goes back in the same place.

Am enjoying following your build.

Keith

[Charles Smitheman]

It's a long while since I last posted on this forum,  hello everybody. 

This build is just up my street, and most helpful to another wannabe machinist, struggling with the basics.

Please keep it up!

The tips are invaluable,  there always seem to be gaps in explanations made in textbooks,  but this real world example somehow makes it all so much clearer.

I have been working on repairing broken engines, as an introduction to making a whole one myself, as my goal.

I managed to make a replacement piston ring for an ST40, which works, but have yet to make a lapped piston and cylinder.

 

Keith, what solvent do you use in your ultrasonic cleaner?

 

Charles 

[KEITH BEAUMONT 1]

Charles, The liquid I use in the ultrasonic cleaner is that supplied by M-DRO for cleaning Carbs. I use it on all metals and it works fine.

Keith.

Edited March 20 by KEITH BEAUMONT 1

[Engine Doctor]

5 hours ago, Charles Smitheman said:

It's a long while since I last posted on this forum,  hello everybody. 

This build is just up my street, and most helpful to another wannabe machinist, struggling with the basics.

Please keep it up!

The tips are invaluable,  there always seem to be gaps in explanations made in textbooks,  but this real world example somehow makes it all so much clearer.

I have been working on repairing broken engines, as an introduction to making a whole one myself, as my goal.

I managed to make a replacement piston ring for an ST40, which works, but have yet to make a lapped piston and cylinder.

 

Keith, what solvent do you use in your ultrasonic cleaner?

 

Charles 

 Hi Charles . For some more realworld tips have a look on YouTube and search for valic000 . Peter Valic is a prolific engine restorer.

He recently made a piston for a diesel using a technique he read about . Its done without the usual and sometimes tedious lapping stage. I tried this method on  a Frog 150 i was restoring and it was quicker and simple with excellent results.

[911hillclimber]

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

[KEITH BEAUMONT 1]

 I can see some high spots in your cylinder so you are not quite there. You really need 1200 grit for the finish and it should look polished when you shine a light into it.

By the time you have finished ,you will have most of the tools for the next one!

Keep at it!😀

Keith.

[KEITH BEAUMONT 1]

I should also have said that with the grit you have used, the inside finish should look an even Grey, before you then use the 1200 grit.

Keith

Edited March 20 by KEITH BEAUMONT 1

[911hillclimber]

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.

 

[911hillclimber]

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,

[Engine Doctor]

You do need a proper fit/seal  for the piston as thats how a diesel works. Looking at your picture of the piston it has rounded edges at the crown . This possibly suggests its not parrallel. These shoulders/  edges should be sharp as thats where the seal is important.

Re the contra-piston you could try the ball bearing and hammer trick.

No its not an early April fool joke.

Lay the CP on flat piece of iron. Find a ball bearing that will fit in the top . It must touch the bottom of the recess. Now tap it smartly. Test for fit in cylinder. Repeat until you get a good tight fit but dont over do it .  If you hit it too hard the CP can shatter but nothing lost . Its a tip I was given many years ago and has saved many hours of making new CP's.

Some CL racing engines that used Cast iron pistons even used this method  on the piston crown to finish races

Externally its looking good.👍

Edited March 24 by Engine Doctor