Swifty's build of Nemett Lynx

[Swifty]

I have been working on the valves today, following the build instructions, I turned the stems over length, finished the valve dia. and turned the valve seat in one setup.



Next I turned the valve caps that will contain the spring, I made sure that they were both the same by using one valve in the head and checking the size of the caps.



Next thing to do was to turn up a bush with a 12mm OD and a 3mm reamed hole in the centre, I then used my new 0.5mm slitting saw to cut through one side of the bush so I can clamp the valves to finish them. I turned the head of the valve down to thickness first on both, then trimmed the valve stems to finished length, carefully checking the finished size to only allow 0.05mm gap under the cams. I had previously marked each valve as inlet and exhaust. Last job was to turn the "E" ring groove, 0.5mm wide. I'm going to have to befriend a micro surgeon to help me get the "E" rings on when the valves are in position.

Here are the finished valves and caps.



Paul.

 

[gus]

The valves look great but how are you going about to lap same.
Will be next week for Gus to work on valves and rings.

Meanwhile I am working at a lame duck space.

 

[Swifty]

Gus, I did manage to lap the valves, but it was difficult. In hindsight, it would have been ideal to leave the stems longer so I could grip them for lapping. But in the end I did manage to get enough grip on them to get a good witness from lapping.

Apart from machining the tensioner, I haven't done much the last few days. Between looking after our grandson and other commitments, there has been no spare time. Tomorrow is another busy day, but after that I will be able to progress further.

Paul.

 

[Swifty]

Well after a bit of a break, I wandered back into the garage tonight and decided to loctite the cams onto the shaft and drill and tap an M3 hole for a grub screw in the timing pulley. I will start to get a move on from now.



Paul

 

[gus]

Great work. Gus is still recovering and the good news is he lost 2 kilos and the bad news is he is not up to cranking speed.

The mini timing gear on the crankshaft. There is no excess to drill/tap to fast same other than Loctite. Please advise.

 

[Swifty]

Gus, you could put a small pin through one shoulder into the shaft, but seeing that the shaft is only 4mm dia. it may weaken it too much. By making the cams out of one piece instead of separate gives a lot more area for the loctite to hold on to. Brian loctited his as two pieces, and so far it seems to be hanging on.

Edit. I had thought of making the cams and shaft in one piece, but decided against it in the end.

Paul.

 

[gus]

Thanks for the good advice. Still lethargic which is good. When the hands moved too fast than the brains,mistakes happen. Still struggling to read prints right and get dimensions,measurements and fits to specs.
Been making too many mistakes and time wasted to rectify. Making a new piece is faster than reworking and compromising. Cutting new outerhead now and about to finish. I have a very good looking pencil stand cum paper weight for my wife.:hDe:

 

[Swifty]

I managed to put a couple of hours work in today, rummaged around and found a suitable spring for the valves and turned up 2 spring retainer washers. With these parts in hand, I assembled the valves in to the head, it took me about 5 minutes on each one to get the E clip in place, I have to work in the tappet hole as the groove on the valve ends up below the surface of the head, making it a real pain to get the E clip on.

The picture below shows the top of the valves, one valve / spring assembly already has the tappet in place on top.



I still need to harden the cams and tappets, but wanted to do a trial assembly.



Paul.

 

[gus]

''E'' clip insertion.
After the umpteenth time putting on and taking of the ''e'' clip , I found a sure fire way. Use a very robust stamp collector's forceps to pick up and insert into valve stem slot. Will try taking foto and post.
New Outerhead about done and I am very happy with same. Looks like I can still reclaim cylinder jacket other than cutting a replacement.

 

[Swifty]

Hi Gus, the biggest problem with the E clips is that I'm working down the tappet hole, I have to hold down the spring and washer then try to put the E ring on down inside the tappet hole. Only have room for a jewellers screwdriver to push the ring in, it's really a three hand job.

Paul.

 

[AussieJimG]

Philjoe05 threaded the end of the valves on his Bonzer so he could easily adjust the spring tension. That might also be appropriate for retaining valve springs in a hole.

Jim

 

[Swifty]

It's done now Jim, but I will keep that method in mind.

Paul.

 

[gus]

Hi Gus, the biggest problem with the E clips is that I'm working down the tappet hole, I have to hold down the spring and washer then try to put the E ring on down inside the tappet hole. Only have room for a jewellers screwdriver to push the ring in, it's really a three hand job.

Paul.

Yes .It is but I did it with two hands. One pushing down the retainer down past the notch. Pick up the ''e'' clip with the right hand and insert. Takes a bit of practice.
Will get my wife or friend to take a close-up shot.Monkey see.Monkey do.

 

[Swifty]

On a trial assembly, the valves seem to be leaking despite initially lapping them, they are a bit hard to grip for lapping, so I decided to mill a groove in each valve to enable the use of a screwdriver. I used a 1mm carbide cutter and made the groove 3mm long x 0.5mm deep, while it was set up, I milled an additional 0.05mm deep groove 90 deg to the slot on the exhaust valve to identify it.



Now to try it out and do a bit of lapping.

Paul.

 

[gus]

Good Idea. With the new Outer-Head,I have to relap the valves.
Valve Spring

Valve springs made with the prescribed SWG 20 piano wire turned out to very stiff. Now looking for one or two size down wire for new springs. Will use S.Steel wire from my fish tackle box.

 

[Swifty]

Hi Gus, I was lucky with the valve spring, I found a spring that was perfect, just had to cut it in half, which gave me the correct length for 2.

Paul.

 

[Swifty]

I'm just pecking away at small bits at the moment, can't seem to get enough time for machining. Despite that, I have made the hall effect sensor holder, with slight modifications to the one drawn. The build instructions call for the sensor itself to be glued or siliconed to the holder, making it permanent, but I'm using the "D" shaped sensor holder that comes with the ignition kit, and will glue this in place. This way it will enable easy replacement of the hall sensor in case it fails.





Now, I think that it's time for a big clean up of my workshop, I always clean up a bit as I go, but its time to empty swarf trays and remove the swarf from corners where it seem to end up.

Paul.

 

[doubletop]

................ I'm using the "D" shaped sensor holder that comes with the ignition kit, and will glue this in place. This way it will enable easy replacement of the hall sensor in case it fails.

Paul

Neat idea

Pete

 

[gus]

I am also pecking away. Will machine the last valve piece,lap and install. After this will stop to '' Bush Engineer'' an electronic speed controller for my friend to load fishing lines. He sells a hundred or two of cheapy M.I.C. Spinners and with free line thrown in. The cheapy M.I.C. Rheostat Sewing Machine Rheostat does last too long w/o overheating.

Now that I am about to really finish up the ''Lynx"",I am enjoying just looking and messing with same.

 

[Swifty]

I spent a few hours cleaning up all the swarf that gets missed on my quick clean ups, I then mixed some degreaser with hot water and washed down the lathe and milling machine, having a knee mill, I spent a bit of time avoiding bumping my head on the table, after that a good spray with WD40 and oil to all the ways.

On to a bit of machining, I had a piece of bronze that was ideal for a flywheel, a bit of a clean up and bore the centre to suit the taper lock on the prop shaft, each side of the bronze had a step on it, so that was just cleaned up and left. Next thing to make will be an adaptor that fits in my battery drill, put a couple of driving pins on it and drill the driving holes on the flywheel.



Paul.