Swifty's build of Nemett Lynx

[Swifty]

I finished turning the nose piece of the engine today, next I set it up in my mill and indicated the centre.


Next, I drilled the fastening holes. I used a circle function on my readout, a lot quicker than using a rotary table.


I used 2 drill bits to locate the nose piece in my vice, then milled the belt hole with an 8mm end mill.


I drilled the fastening holes in the cylinder the same way I did the nose piece.


I thought that the easiest way to drill the holes in the cylinder that hold down the head, was to attach the cylinder to the crankcase. This solved alignment problems, all I had to do was find the centre. I worked out the holes positions with basic trigonometry and drilled all my holes. I will use my tapping stand to tap the blind holes.


And here is another assembly with a few more parts on it. The cylinder hold down screws are a real pain to do up, I'm considering tapering the last few fins or milling grooves to allow better access with a hex key. I took this photo before I drilled the rest of the holes in the cylinder, but you can see the screws in the photo above.


Paul.

 

[Jasonb]

Have you tried a ball ended hex wrench, the ones on the bobcat are the same but can be driven with one of those. A cut down "L" key will do to finally tightening

 

[Brian Rupnow]

Swifty---Looking very, very good.---Brian

 

[Swifty]

Have you tried a ball ended hex wrench, the ones on the bobcat are the same but can be driven with one of those. A cut down "L" key will do to finally tightening

Hi Jason, that's exactly what I used, even with the ball end key, it was still a pain. I cut up an old key to do the final tightening.

Paul.

 

[gus]

You are making good process .th_wav
Gus is still trying to get out the mess of the Outer-Head. :wall:
Planning to use the 10mm Champion plug. Have reports about the 1/4'' plugs easily gets fouled.
I am now making a DIY counterbore to recess spark plug hole. Using Grade 8 hex bolt.

 

[Swifty]

Brian, thanks very much for your comment, I'm trying to keep all my machining neat and tidy looking.

Gus, I started on machining the head today, the spark plug was one area I was not sure about. I immediately thought about using a 10mm thread plug as I have one left over from the Rupnow H & M, but I'm concerned that it will be too large. The thread may interfere with the valve, and a larger counterbore is needed to get a tube spanner in, which may also interfere. I don't have any other plugs, and would have to buy the tap as well as the plug. The other option is to make a plug from scratch, I will consider my options for a while longer.

To the members that make their own plugs, what is the central pin made out of, I seem to recall that some just use silver steel, would a TIG welding electrode be feasible ?

Paul.

 

[AussieJimG]

Have you thought of using hex headed screws to hold the cylinder?

Jim

 

[Swifty]

Have you thought of using hex headed screws to hold the cylinder?

Jim

That's an option Jim, I just checked the across corners size and it just a bit less than 8mm, so there is still room to turn them. However, I just seen to like the look of cap screws on this engine.

Paul.

 

[gus]

Brian, thanks very much for your comment, I'm trying to keep all my machining neat and tidy looking.

Gus, I started on machining the head today, the spark plug was one area I was not sure about. I immediately thought about using a 10mm thread plug as I have one left over from the Rupnow H & M, but I'm concerned that it will be too large. The thread may interfere with the valve, and a larger counterbore is needed to get a tube spanner in, which may also interfere. I don't have any other plugs, and would have to buy the tap as well as the plug. The other option is to make a plug from scratch, I will consider my options for a while longer.

To the members that make their own plugs, what is the central pin made out of, I seem to recall that some just use silver steel, would a TIG welding electrode be feasible ?

Paul.

Hi Paul,
Saw your message while fishing far out at sea and could reply due to lack of line.
Drilling the spark plug from top is risky and no guarantee,I won't hit and destroy valve holes. I drilled from bottom up. Some end milling required so as to make drilling spot on.Must ensure you get the 25 degrees angle. See fotos of top and bottom Outer-head. I used my DIY boring head to counterbore top to take spark plug.
Good Luck. Gus will work crankcase tomorrow. Fishing not too bad today but my friend landed a 4 kg Barra.

 

[Swifty]

Hi Gus, I've been working on the cylinder head for my engine today, I'm still undecided about the spark plug. I will post some pictures tomorrow. I have ordered a 1.5mm slitting saw to machine the grooves in the top, so will have to wait for that to arrive. Still have plenty of other parts to work on.

I received my toothed wheels and belt from a local supplier the other day, one thing I didn't realise was that the spigot on the small wheel will disappear when I bore the hole in the centre. No problem though, I have decided to make my own wheel by broaching the teeth.

 

[gus]

Hi Gus, I've been working on the cylinder head for my engine today, I'm still undecided about the spark plug. I will post some pictures tomorrow. I have ordered a 1.5mm slitting saw to machine the grooves in the top, so will have to wait for that to arrive. Still have plenty of other parts to work on.

I received my toothed wheels and belt from a local supplier the other day, one thing I didn't realise was that the spigot on the small wheel will disappear when I bore the hole in the centre. No problem though, I have decided to make my own wheel by broaching the teeth.

Hi Paul,

I used 2mm end mill to cut the O/H slots/fins. Was nail biting. With only 2 short and shallow groooves to cut,I took my time and came out with good fins/grooves and no broken 2mm mill.

Now about work on crankcase. Taking my time and taking note of vital dimensions. Will be fun.

Fishing yesterday was not the best with fishing guide but we were happy with the 4 kg Barra and Snappers. Can be viewed on my FB.

I am about to look for timing gear and belt.

 

[Brian Rupnow]

Gus--I just spent most of the day machining the crankcase body for my engine, which is based on a similar engine by the same gentleman who designed the Lynx.--I will tell you right now----You are in for a LOT of milling.---Brian

 

[Swifty]

I have decided to go with the 1/4 x 32 plug, I have ordered the tap, plug and ignition today from Australian suppliers, so will see the parts shortly.

Gus, the slitting saw is nearly cheaper than buying one small cutter, the only problem is that I will have to make a new holder as I could not get a bore to suit my existing holder.

 

[Swifty]

The postman bought 2 presents for me today, my 1/4x32 tap from a local supplier and my 1.5mm slitting saw from Shanghai. I paid $6.93 including postage for the saw and included in the package was a $5 voucher for my next purchase, great will have to see what else I need.

Now I have to make a holder for the saw, then continue on with the head.

Paul

 

[Swifty]

After making a holder for the new 1.5mm slitting saw, I could carry on machining the head. The saw saved heaps of time, too me about 10 minutes to mill all the slots in the top of the head. The only things left to do now are to counterbore the spark plug hole, I'm waiting until I receive the spark plug to check the counterbore depth required, and tap the M2 holes that hold the carby and exhaust on.





The cylinder head has been the most involved part so far, a lot of operations.

Paul.

 

[Swifty]

Access to the screws to tighten the cylinder to the crankcase has been on my mind for days, the screws were a bit hard to get to with a hex key. I decided to bite the bullet and machine some clearance in the fins to aid in getting a key in there. There's no turning back now, however I think that I like the look of the cylinder this way, it breaks the "finny" look up a bit.



Paul.

 

[gus]

Hi Paul.

That was a good idea cutting into the fins. A bit dicey. And good aiming too. And good looking.I may have to do the same for the screws. One step at a time.

 

[Swifty]

It was actually quite easy to machine the grooves through the fins, I mounted the cylinder on the crankcase with one screw, held the crankcase in the vice at 20 degrees, centred the cylinder and moved in 5.5mm from when I touched the first fin. After that, I just undid the one screw and rotated the cylinder until all the grooves were done.

Paul.

 

[gus]

Gus--I just spent most of the day machining the crankcase body for my engine, which is based on a similar engine by the same gentleman who designed the Lynx.--I will tell you right now----You are in for a LOT of milling.---Brian

You are right. With a very small milling machine,excavating took ages. After 4 hours today and two more tomorrow,I am about finished. That dead tired ,body and soul. Looking backwards,perhaps I should have used plates to fabricate crankcase. :wall:The major parts done. Will be quite a story to tell when I meet Paul and AussieJim and RodW when we get together at the Melbourne Model Engine Show in October 2014.th_wav

 

[Brian Rupnow]

I've always wanted to visit Australia. October, ---Let me talk to my wife---