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Member postings for John Roberts 10

Here is a list of all the postings John Roberts 10 has made in our forums. Click on a thread name to jump to the thread.

Thread: Whittle V8 Camshaft and Conrod Collision.
11/10/2018 23:34:57

Jeff,

Thank you for your comments.

The head gasket is a thin copper ring between cylinder and head. I used copper grease to help seal. I did not check for leaks here as all cylinders were machined at the same setting so each bank of four should be on the same plane.

I will immerse the engine in white spirit to check for leaks here. then try adding silicone to joint faces as suggested .

I did run the engine first with it totally submerged in oil with lower crankcase removed and no plugs fitted at a few thousand RPM finishing at 5000 rpm using a prop starter with it fully assembled. Cylinder bores are polished from this process with most radial honing lines removed..

The valve stem to valve clearance could be increased and was something I intended to do as there is little axual play at present. I did not re ream valve guides after pressing in to head.

I found that if the crankcase had too much oil in there it would get past the each ring and fill up the glow plug with oil. For me I found the correct level was just enough for the crankshaft to dip into and through up the bores.

The valve seating were tested by immersing the heads in white spirit and blowing though a tube connected to each manifold in turn. Air bubbles were seen with little improvement after further lapping. This is why I intend trying stiffer valve springs.

I hope these observations might be of interest to other builders of this engine.

11/10/2018 18:04:37

Yes I can clarify that relief on one side if the con rods is necessary. I attach photo of the finished engine. For me the biggest challenge is getting the engine to run. I have now a power supply which gives correct power to glow plugs and tried a high nitro fuel, but there is air leakage though the valves despite grinding/lapping valves in. The next option is to try more powerful springs and possibly remaking pistons which are taller. The hope of raising compression. I am confident that I have timed correctly. Any one in the process of making this engine take an extra effort to prevent air escaping other wise you will be in the same boat as me.

My attention has now moved on to making the Blackmore Bentley BR2 Rotary engine. I would be very interested in contacting anyone that has made one as I have some questions!!

p1010751.jpg

Thread: Myford Oil gun nossle missing
10/02/2017 21:47:15

HI I have lost the brass nossle that screwed onto the end of my Myford oil gun supplied with the Myford 254 lathe. This oil gun differs to the one I had for the ML7

Would like to make a replacement. Can anyone do a drawing of theirs with dims or lend me one to copy. Thanks in advance.

Regards John..

Thread: Ball screw thrust bearings .Wabeco Cnc milling machine
13/05/2013 21:43:44

Hi John,

Thanks for your detailed reply. I will try and replace the standard ball bearings with angular contact bearings. There is a thread on the ball screw and preload as adjusted by screwing belt pulley against bearing. It is cross drilled and tapped to lock in position with grub screw.

Not sure shealded angular contact bearings are available. I will have to ask tomorrow.

Regards John.

12/05/2013 19:10:50

Hi, I was removing the ball screws from my Wabeco CNC mill and noticed that the pairs of thrust bearings were ordinary ball bearings. Surely these should be angular contact bearings which are designed to take end load. Do other bench CNC mills have these fitted. I thought that to remove all ball screw end play, the bearings have to be preloaded. One also has the weight of the spindle assembly and motor pushing down on it. I thought that ball race bearings are not ment to have an end load applyed

I would appreciete any comments on this matter.

John.

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