Attempting Gordon Nano

[creast]

After a reasonable success (at least a running engine) of the Clanford Clan, I decided that self flagellation was the key to getting through Covid19 crisis.
So , I have started to tackle the Nano 0.1 cc engine by Richard Gordon.
I am gobsmacked by the quality and intricacy of design produced by such a young enthusiast at the time.
I know this is going to be a demanding project with some tricky thread turning.
My equipment is probably as basic as the author had but my skills are less so.
However, first was the crankshaft and this was turned from EN24T which is pretty horrible to turn on my lathe but with care and some polishing to finish came out pretty well.
The crank pin was turned by the usual method of a split bush with 2.5 mm off centre bore.

 

[creast]

Although I still have to machine the crank webs (I only just realised) I moved on to the cylinder.
This I found quite tricky. The threads are only 0.5mm pitch (50 tpi on my lathe) and I can only guess what a nightmare doing the internal threads will be.
To avoid two setups I decided to thread both ends in one go. This meant stopping the lathe and manually rotating the chuck to get close to the exhaust shoulder.
The inboard side could run out easier into the stock bar.
My thread turning isn't great and the mild steel rags like a bitch. However I got a thread of sorts.
After doing this I saw a Youtube video by Joe Pieczynski where threads can be cut with reverse rotation away from a shoulder so I will definitely try this.
Next I need to make a port cutter. Sounds like fun???

 

[creast]

Its funny how often a project ends up being more than just making the parts. Its all the things you have to make to achieve it!
So, I made my cutter, 4 blade as opposed to the authors 3 blade, from En24T and hardened and tempered it. It would be nice if it was a 2o tooth or so but there are limits to my abilities!!
Also I realised I would need to make some fixtures to hold the cylinder for the machining as I wasn't intending in following the author method of milling in the lathe.
So, a threaded bush to hold the cylinder in a rotary table and an angle jig for the drilling of the transfer ports.

 

[creast]

Not much achieved today as other chores demanded attention.
The port cutting went well and I didn't break the cutter!! Being 0.8mm thick it is quite delicate!
I was extremely cautious on feeding the cutter in as it is quite easy for the cylinder to unscrew under the cutting forces but all went well.
Transfer ports now need to be drilled and the bore lapped.

 

[creast]

Today I drilled the transfer ports using a jig at 45 deg. I confess I eyeballed the position although the offset distance was dialled in using a pointer from the datum edge.
Next is lapping which I normally do with a short split lap but I didn't have a suitable one this small so decided to make a different design.
Basically, two cylindrical rods milled to half diameter, soft soldered back and turned to the finished diameter for the job.
Centres and ferrules also made for keeping it together when separated by de-soldering and cleaning off the solder from the faces.
In use, one end is held in the chuck and the other in a dead centre, the ferrules keeping it together.
Paper shims are added to increase the diameter and being a long lap gives better control of diameter. Or the theory says!

 

[awake]

Nice idea on that lap design!

 

[creast]

Nice idea on that lap design!

Thanks Andy,
It is certainly easier to use and adjust compared to my previous efforts.
I always find lapping is always difficult around the ports and always creates a tighter region, Not sure if anyone can advise?
As such, I resorted to a localised lapping tool to fine tune the final fit which is still a little tight but will address this later.

 

[creast]

Today I made the piston and went through the process of lapping to fit the cylinder. machining was fairly straight forward apart from the conical top.
My lathe, Myford ML7, only swings 45 deg either way on the top slide so to part off at 10 deg meant some jiggery pokery.
Some impromptu clamping was in order! See pic.
Unfortunately I had approx 8 degree rather than 10 but I will run with that and make the contra piston to suit.
Next was the wrist pin. What a watch makers delight?? I mean, lightening the pin by drilling a 0.5mm hole thro' in silver steel!!
Oh well, I decided to have a go but I only had a 0.6 mm bit.
I used my pin chuck loosely held in the tailstock and fed it by hand and voila! I am amazed I didn't break it.
I do think this detail is a bit anal tho!!

 

[awake]

Wait - there's a piston in that picture? I thought that was a speck of dust on the camera lens ...

I cannot imagine attempting anything that tiny!

 

[creast]

Wait - there's a piston in that picture? I thought that was a speck of dust on the camera lens ...

I cannot imagine attempting anything that tiny!

Me neither!! Ha ha ha!
I must be going crazy!

 

[awake]

Well, there's bad crazy, and then there's good crazy - I trust you are the latter!

 

[creast]

Well, there's bad crazy, and then there's good crazy - I trust you are the latter!

I hope so.
This lock-down here means I can get away with more time in the 'man cave' since other household maintenance has been pretty much addressed already in the last few weeks.
I hope you and family are keeping well in similar circumstances?
Rich

 

[creast]

Today I was so involved in making parts I didn't take any pics of the methods I used.
The cylinder head was turned from 6082 Alum alloy and the fins/grooves cut with a custom parting tool I knocked up from an old jigsaw blade.
These work great on aluminium but rubbish on steel.
I also used the reverse threading from a fixed stop and will not go back to the conventional method. It's just so easy to work to a fixed depth and no crashes!
I cheated on the compression screw by loctiting a threaded bush to commercial crew and then cross drill for the T bar.
Tomorrow I need to concentrate on an indexing mod to my old Myford., so a break from this watchmaking engine!

 

[awake]

So far so good. Unfortunately, working at home has turned into "let's have lots and lots of virtual meetings, since it is so easy to do."

Which is another way of saying that I have not been able to get out to the garage nearly often enough. I really hate it when my job gets in the way of my hobbies ...

 

[awake]

Nice idea on the grooving tool, and great results!

 

[creast]

So far so good. Unfortunately, working at home has turned into "let's have lots and lots of virtual meetings, since it is so easy to do."

Which is another way of saying that I have not been able to get out to the garage nearly often enough. I really hate it when my job gets in the way of my hobbies ...

My sympathies to you!
I am blessed by being retired but sometimes my hobbies wind up my good lady

 

[creast]

Well, I am glad I took time off to make an indexing fixture for my ML7 which uses a 60 tooth gear on an expanding mandrel into the lathe spindle bore.
The attachment uses existing holes in the lathe to save desecrating the Myford

Doing these small engines often requires transferring part machined parts from lathe to milling machine and I often find it very difficult to pick up features accurately. Not to mention my cheap Chinese DRO often goes AWOL!
So now, combined with my homemade milling attachment that fits to the cross slide, I can be certain I am machining cross holes or flats / hexagons with some confidence.
I just used it to create the serrations on the prop drive.

 

[awake]

Very nice!

 

[creast]

A little more progress.
To start on the crankcase, a cube of 21mm was hacked from 32mm dia 6082 Alum alloy bar and transferred to the 4 jaw for boring and threading.
Since the depth of thread is only 1.5mm the only way to thread is in reverse from a stop and going outwards (unless you have the luxury of a cnc lathe).
As per the article, a threaded madrel was also made to hole the crankcase during further machining operations.
Machining this part is quite involved with multiple setups involved.
One part I didn't like was machining the transfer ports into the threaded cylinder mounting thread as this rolls over the thread quite badly (well mine did) and required some eyeglass deburring.
I guess putting the ports in first may also have issues due to the nature of intermittent cuts.

 

[awake]

When you say the thread is only 1.5mm deep, are you talking about the thread that is showing at the top in the last picture above? I'm thinking this is where the cylinder threads in - ?

In any case, continuing to enjoy this thread, and marveling at the teeny tiny work involved!