Old Sckool 5 cc model Diesel engine build

[sladey]

Nice work

[911hillclimber]

Thank you Mark.
This thread is very well watched but few comments!
But you know how that feels.

Back on the job this afternoon to do lots of details before starting on the crank shaft, then the very hardest bit, the con rod.

[hot66]

I’m enjoying your updates Graham

[911hillclimber]

Thank you James.
I'm a bit worried they are daily updates, but this project is keeping my tinkering spirit alive every day almost and getting obsessive much as my Lola build was.

Made some significant progress this afternoon in as much as actually finishing the parts so i can move on to the Big Challenges ahead.

Silver brazed the inlet stub to the cylinder that certainly blackened it!
That was followed by soft soldering the transfer porting cover to the cylinder as well, and that added to the scruffy look....

I last silver brazed/soldered back at school for my GCSE in metalwork which I got a distinction in (and Art). Those were the days.

The school was a bit off-the-wall in those days (60's) and there was an after school Club for all subjects, so I did metalwork where the game was to do anything outside of the curriculum, so we cast metal (!), brazed, and cut and made nice things.

I really wanted to be a jeweler as a career, but my father was not so sure (he was an architect) so i did a heavy engineering apprenticeship instead.

The crank case is all done, cylinder studs in and loctited and it all screws together!
Amazing for me and my skill base.

A few pics as ever, but I'm getting excited.

[911hillclimber]

Another great few hours this afternoon on the engine.
Felt in the mood to start the crankshaft.
Big lump of En8, 3 1/8" long, bit of a tease to machine.

Has some inspiration to how to set the bar up to machine the crank pin 7/16" off centre to set the throw of the crank/rod.

Found my Vee blocks and clamp i made when 16 in my first year as an apprentice, and put faith in those parts being accurate (!)First time I have ever used them in 54 years.

The Vee block mounted well on the 4 jaw, the hold being really sound and stable and the final jaw clamped the crank bar 'blank' tight and the stirrup clamp I made back then secured the top. The pics say it all.

First few cuts were super light to test all is well. The mass turns as a blurr with almost no reference to the lathe to assure yourself you know where you are.

This is the mother of all intermittent cuts, and a bit nervy to say the least.

I have kept a check on the chuck jaw tightness!

Leaving the pin well oversize (it is 1/4" dia when done) and only 3/16" long.

This has perplexed me a bit since I bought the design, but seems to be working out so far.

A lot more swarf to generate yet.

[911hillclimber]

Cold in the garage recently...
So been discussing elsewhere about the merits of HSS cutting tools v modern ceramic tips which I have been using. (as pic above)

Hoping to try some suggestions to see if i can cut more/pass and get a better surface finish.

Ceramic tips do not like at all intermittent cuts or light ones either.

[MBEngineering]

HI 911hillclimber

try changing the carbide tips for a silver one for Ally' and lighter cuts, or turn the one you have in now over, or have you used that side all ready, or some decent insurts, mybe a look hear https://www.youtube.com/watch?v=NdLtZLZZQz8 on tooling/speeds

your next project after this is hear ; https://www.youtube.com/watch?v=k5grnbla2wY all made from off cuts/scrap/what ever you have lying around

regards mike

[911hillclimber]

Toooo hard Mike!

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!

[911hillclimber]

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.

[911hillclimber]

Spent a few hours fixing this bloody crankshaft.

On the advice from another on an engineering forum 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.

Plan/advice is to remove the machined crank pin and drill the crank web the right stroke and drill 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!

[911hillclimber]

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)

[911hillclimber]

As an aside, I track the progress of these little 'off the wall' threads of mine and it seems that very few responses, but a huge number of views, average about 1100 each 24 hours!
This helps me feel it is worth doing the thread (bit like Sladey suffered)
It the View Counter working correctly or 100 times in error??

[Hugo 356]

There’s an outside chance that while facilitating your avid human reader’s vicarious machinist dreams, you’re inadvertently teaching AI bots how to power the army of drones that will lead to mankind’s downfall

[911hillclimber]

The crank is hard work, not only because it is in En8 but making things fit.

I've modified the design to make it much simpler to machine to drive the propeller, but the next step is to shape the crank web to get some level of balance.
The design is known to be unbalanced but you can close in on the ideal.
The engine is a low revving design long stroke, so that helps.

Last few days have been all a bit motor sport duties'' at the Club's events, and much more to come soon so slowing progress.

Some difficult milling to come!

Hill climbing season starting to unfold.

[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 he cast iron cross slide knocked out of it, it has led a hard life in the past. It has it's limits!

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.