21:09 - Camera excursion when the lathe isn't rotating the chuck. 24:49 - A lot of eccentricity between rim of the chamber and the cylinder socket. 25:54 - 1) Who is responsible for the geometric relationship between the piston dome and the chamber? 2) If this is a twin, are you modifying the other head for consistent C/R?
Yes, the picture wobble must have been just from the motor vibration, I guess. The eccentricity of the combustion chamber wasn't at all noticeable until the head was spun in the lathe - must have come out of the Ducati factory like that! Deliberately? or due to Production tolerances? Ducati must have allowed plenty of clearance between the piston dome & combustion chamber. This is just a single.
@@MidEngineering Having many years of experience in the activity (lawn mowers to Mouse moters to Porsche 4 and 6 cylinders to 250 Ferraris and DFVs), I can say you have no business doing what you propose doing. Give it back to the owner to save them money.
@@MidEngineering It is not my intent to offend, and your tool design suggests you are very talented as a machinist ('engineer' in Brit? Me too), but 'allowing plenty of clearance' is fine for lawn mower engines. High performance engines require very controlled quench clearance at the periphery of the chamber to allow high compression at low ignition lead numbers. If you and the owner have not agreed upon that number, there will be difficulties. Again, I have been building no-performance lawn mowers to Cozzy DFVs since the '60s and do have considerable (dyno-tested) knowledge regarding the issues involved.
@@SettledBatches I just did what I was asked to do. The owner had a cylinder head that wouldn't seal on the barrel. Now he has a properly working motorcycle. He installed an appropriate shim/gasket to compensate for the small amount of metal we machined off the head & keep the standard compression ratio. I think he knows his Ducati singles & I guess the bike is pretty much to the spec. it left the factory 50-60 years ago as a production road going bike.
Did you check the runout of the outer face when setting up on the lathe? If that wasn't affected by the weld repair it would be your best surface to dial the inner face that needed to be machihed square to the axis as they were probably machined on the same setup in the factory. That face has to be dead nuts square to the axis of the cylinder given that this is a bevel head and and any deviation would negatively affect the meshing of the camshaft bevel gears. From other comments I understand it worked out fine but I had to point out the above detail about the gear mesh. The fixture was brilliant by the way.
You should tighten the four "dowel" screws one at a time instead of loosening them all and tightening them all each time you are trying to position them. The way you did it ensured you introduced the maximum number of variables each time - not the way to arrive at a result in the quickest manner.
I don't think I did! This was actually a couple of years ago (!) so I'm not sure of the details but I think there was plenty of clearance there. @colinmartin2921 would know...
@@MidEngineering if it didn't come back as a reject then it must have been fine. Some bikes seal on inner and some seal on the main one and the inner bore is purely for location. If they sit on the inner, the depth can be important, either to seal or prevent distortion when torqued down.
I fashioned an aluminium gasket to replace the metal that was skimmed off, as I didn't want to affect any other variables. So far everything is working fine!
love that fixture.. great work..
It is great to see how you made the fixture plate for the head. That was a lot of work but it looked like it turned out great
Life of a jobber. 98% set-up 2% task....... Nice work.
Very clever solution.
I trust you remember this Colin! Can you shed some light on the question raised in Chris Stephen's comment?
21:09 - Camera excursion when the lathe isn't rotating the chuck.
24:49 - A lot of eccentricity between rim of the chamber and the cylinder socket.
25:54 - 1) Who is responsible for the geometric relationship between the piston dome and the chamber? 2) If this is a twin, are you modifying the other head for consistent C/R?
Yes, the picture wobble must have been just from the motor vibration, I guess. The eccentricity of the combustion chamber wasn't at all noticeable until the head was spun in the lathe - must have come out of the Ducati factory like that! Deliberately? or due to Production tolerances? Ducati must have allowed plenty of clearance between the piston dome & combustion chamber. This is just a single.
@@MidEngineering Having many years of experience in the activity (lawn mowers to Mouse moters to Porsche 4 and 6 cylinders to 250 Ferraris and DFVs), I can say you have no business doing what you propose doing. Give it back to the owner to save them money.
@@SettledBatches Huh?
@@MidEngineering It is not my intent to offend, and your tool design suggests you are very talented as a machinist ('engineer' in Brit? Me too), but 'allowing plenty of clearance' is fine for lawn mower engines.
High performance engines require very controlled quench clearance at the periphery of the chamber to allow high compression at low ignition lead numbers. If you and the owner have not agreed upon that number, there will be difficulties. Again, I have been building no-performance lawn mowers to Cozzy DFVs since the '60s and do have considerable (dyno-tested) knowledge regarding the issues involved.
@@SettledBatches I just did what I was asked to do. The owner had a cylinder head that wouldn't seal on the barrel. Now he has a properly working motorcycle. He installed an appropriate shim/gasket to compensate for the small amount of metal we machined off the head & keep the standard compression ratio. I think he knows his Ducati singles & I guess the bike is pretty much to the spec. it left the factory 50-60 years ago as a production road going bike.
Did you check the runout of the outer face when setting up on the lathe? If that wasn't affected by the weld repair it would be your best surface to dial the inner face that needed to be machihed square to the axis as they were probably machined on the same setup in the factory. That face has to be dead nuts square to the axis of the cylinder given that this is a bevel head and and any deviation would negatively affect the meshing of the camshaft bevel gears. From other comments I understand it worked out fine but I had to point out the above detail about the gear mesh. The fixture was brilliant by the way.
You should tighten the four "dowel" screws one at a time instead of loosening them all and tightening them all each time you are trying to position them. The way you did it ensured you introduced the maximum number of variables each time - not the way to arrive at a result in the quickest manner.
Is there a sealing joint that fits there or is it metal to metal facing .
Metal to metal.
@@MidEngineering Thanks .
Quite a lot of work to save the head, but probably worth it. Did you skim the other face to keep the depth within tolerance?
I don't think I did! This was actually a couple of years ago (!) so I'm not sure of the details but I think there was plenty of clearance there. @colinmartin2921 would know...
@@MidEngineering if it didn't come back as a reject then it must have been fine. Some bikes seal on inner and some seal on the main one and the inner bore is purely for location. If they sit on the inner, the depth can be important, either to seal or prevent distortion when torqued down.
I fashioned an aluminium gasket to replace the metal that was skimmed off, as I didn't want to affect any other variables. So far everything is working fine!
Did this increase the compression? Did it reduce valve - piston clearance? Don't know much about Ducati except desmodromic valve train.
The owner added a thin aluminium gasket to keep the original compression ratio & valve to piston clearances.