JB Atoms

Unfortunately I have too much space, a partner who tolerates my mess, and I subscribe to the 'first available horizontal space method of storage!'

How AWFUL as long as you are happy with it then its not a problem to anyone else
Theres a villa up for sale near me i think you would like it in Cyprus Tony :whistle: :whistle: :whistle:

Sorry I'm late getting onto this I missed it until now. Re crankweb I know that is why the cut is made but at that size many were left complete .Apparently with no deleterious effects.on the balance/vibration. Re the shaft taper could you not just have taken it further back up the shaft allowing the driver to sit further on the shaft.? Just a thought. Nice job on the conrod Sir
John O/T

THE BLACKBIRD wrote: How AWFUL as long as you are happy with it then its not a problem to anyone else
There's a villa up for sale near me i think you would like it in Cyprus Tony :whistle: :whistle: :whistle:

I wish, trouble is, the Rand is going down the toilet!

one tenor wrote: Re crankweb I know that is why the cut is made but at that size many were left complete .Apparently with no deleterious effects.on the balance/vibration. Re the shaft taper could you not just have taken it further back up the shaft allowing the driver to sit further on the shaft.? Just a thought. Nice job on the conrod Sir
John O/T

I have a CS MiIls twin, it doesn't have any balance web (just a continuous circle) and the vibration is terrible, I would hate to use it in a model!
Re the taper, in engineering I've found it's always best to quit while you're ahead, plus, the complete one has nearly as much end float! So I'm going to make up a new thrust for that as well.

OK Tony you know best I'll shut up :lol: As it happens I have added thrust washers to a number of my engines as the manufacturer left loads of float on the shaft..35 / .40 sizes seem to be the worst. Even more important with pusher designs. I found one with the backplate heavily scored by the crankpin. The endfloat was about 5/32 in. I don't know what the engine was as there were no markings on it. Somebody stole it from my flight box when I was flying .Can't imagine what. It was that attracted them to it as it wasn't what I would call a . handsome motor I suspect it was an Eastern block job or maybe a shed made one. A bit rough round the edges.

Hi Tony ! Did the missing NVA needle turn up yet ? If not it'll likely as not turn up when you've made 2 replacements at least according to Sod's or Murphy's or someone's.Have you looked in the vacuum cleaner for it or the grooves in your shoe soles? Assuming they have grooves of course. I've found a round webbed crankshaft with the bit where the pin should be snapped clean off . I'm going to take pics of some engine woes then see if I can post them here. I'm trying to get my head round the lovely camera John( Firewood ) sent me. Fingers crossed cos I'm phick :silly: Then there is adding script to go with the pics. I know there is a posting on the site about doing this. I'll have a hunt for it. Going to eat now .TTFN John O/T

The needle valve still hasn't surfaced, so


Free hand cut a piece of flat bar, put it in a 4 jaw chuck and make it round. Because I have to drill so far I'm worried about the drill wandering off so I'm going in with a 0.8mm slot drill. It's quite time consuming because you have to 'peck' at it to remove the swarf.

Turn it around and drill 1.6mm

Oops


I should have realised I was trying to grip much too short, so now I'm going to do the venturie side complete first.


The needle valve holes in the venturie have been drilled out 3.5mm so I'm going to finish turn to 3.5mm but I must undercut the part inside the venturie to the original 3.2mm (1/8")


And thread it.

Next up, cut the fuel tube side.


With undercut and taper for tubing which the original didn't have.

And part off
Then make a needle, Neanderthal style, spin in chuck and touch with an angle grinder!


Finished


I added 2mm to the length so I could use these little 'O' rings, the venturi is in very poor condition.

Well done Klip but I didn't see the cross flow holes done .Did you film it?

The cross holes were done on a pillar drill with a .8mm slot drill, I'll take a pic on the next one.
Well I've spent 2 days trying to start this one without success! I have fuel and I have compression. I have stripped it again and found this.


If you look closely the collar that hold the gudgeon (wrist) pin is wearing away, or possibly extruding. Either way 2mm up and down movement is not going to work, so now I'm busy making a new collar to my specifications.

Which one is that from Tony ? The complete one or the one missing the shaft. It might tell me how this deformation occurred .They are usually good starters but 2 mm play is a huge amount of play on conrod length .It would make all the difference .Thanks for sorting it out Tony. Regards John O/T

This is all to do with the one with the missing shaft, on the 'good' one the gudgeon pin appears to be an interference fit in the screw collar. Another thing, the gudgeon pin appears to be too short. The distance between thread peaks in the piston is 10.42mm and the pin is 9.62mm long, = .8mm short. The inside diameter of the collar is 7.42mm so in theory we have 1.5mm of land each side as a bearing surface. Minus the .8mm short, the pin is always going to move to one side or the other, which leaves us with .7mm bearing surface on one side. It's definitely going to fail!
People with machining experience will know how difficult it is to re-centre a component once it's been removed from the chuck, which is why I try and do everything I can in one setup.


I even checked the fit of the needle valve before turning it around to finish off.