Mastiff lc mason engine REDO .

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Hi Minh,
I built a Mastiff (finished in 2018) and wrote up the build on the Model Engine Maker forum. My description of making the pistons and cylinder liners is in
Len Mason's "Mastiff" - chewed from the solid
I think that Len Mason's reason for making the pistons in two parts is so that the internal shape of the gudgeon pin bosses can be machined. Without the two-part construction it would be necessary to make the pistons from cored castings. If you use the cast iron pistons, then you will not need to adjust the diameters for temperature difference and the liners and pistons can be lapped to a fine finish. If you go for aluminium pistons then, as you describe above, you need to allow for the expansion of the piston as the engine warms up. In my engine the cooling water doesn't get anywhere near boiling, but I haven't measured the temperature, I don't think that the cylinder liner would reach anything like the 150-200 C that you mention. If I'm estimating it correctly then for a 100 C temperature rise a 25 mm piston will increase in diameter by about 50 microns - 0.050 mm. Others should check this!

Hope this helps!
David

Hi David
Thank you.

Regarding cylinder finishing, it is not a problem
The reason I use aluminum pistons is because it is light
Yes, 150 to 200 degrees Celsius seems much , but if the piston fits tightly into the cylinder at that temperature I wouldn't worry about it getting stuck due to thermal expansion.
And the crankshaft only has 2 bearings at both ends. - One mistake will damage the crankshaft
Maybe I'm too <safe>, after all a little <safe> is better 😅
 
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Hi David
Thank you.

Regarding cylinder finishing, it is not a problem
The reason I use aluminum pistons is because it is light
Yes, 150 to 200 degrees Celsius seems much , but if the piston fits tightly into the cylinder at that temperature I wouldn't worry about it getting stuck due to thermal expansion.
And the crankshaft only has 2 bearings at both ends. - One mistake will damage the crankshaft
Maybe I'm too <safe>, after all a little <safe> is better 😅
I just made aluminum pistons for my Mastiff and they work fine.

Ron
 
Hi All !
An update
I just made a valve seat for testing, everything is fine
Even though the valve seat is pressed into the block, it still has a bolt to hold it in place

20240119_A.jpg
 
Hi All !
An update
I did the valve seats, and made a part to press the valve seats into the block, everything went according to plan . Valve seats are pressed into the block, With quite tight tolerances there will be deformation so I will make a tool to recut the surface

20240121_A.jpg
 
Last edited:
Hi All !
An update
I did a tool to re-cut the valve seat surface
After having to re-sharpen it a few times because it can't cut.... I realized the blade material was too soft compared to the valve seat material, it wore out quickly.
Conclusion : Don't work with materials that I don't know what type of material it is.

20240128_A.jpg
 
Yup, mystery metal. I have come across this many times.
When I figure out I have no idea what it is I usually label it "SIW"
Because I all I really know is it " Sinks in Water" ( use at your own risk )
I have several pieces of "SIW" reserved for non critical tasks :)

I am glad you found something that worked !!!

Scott
 
I saw some castings in a shop once, awaiting machining. Most were marked "HW". When I asked, I was told "Holds water". That was deemed good enough in the foundry. I.E. If badly cracked, they leaked.
A bit like the regular "US" marking for un-servicable, or "MT" marked on used gas cylinders...
Must be loads of anachronisms, anurisms, analogues, (what is the word?) or whatever out there....
K2
 
Hi All .
An update:
The valves are done, they have been lapping

20240219.jpg


I had a plastic spacer to prevent grit from getting into the valve guide, but it was missing. I used paper to replace it.

20240219 z.jpg



20240219_v.jpg
 
Hi All .
An update:
I changed some dimensions to mm and tested: everything is fine,
Piston: I will make 2 rings, it's not necessary but I like 2 rings

piston , con rod change.jpg


20240222_105758.jpg
 
Hi All
I was making pistons, when I cut the groove for the ring and looked at it through a magnifying glass and I noticed it was not a perpendicular groove.

20240222_162836.jpg


After considering every possibility....and this is the reason

20240222_A.jpg
 
100% it can be the cutter. Ideal world yes the cutter is moving perpendicular to the work and should cut a parallel groove. Real world everything is made of rubber and the angle of the tool causes it to deflect as it engages the material. I can't tell you the number of times I've parted off a bar with a badly lined up tool, and the cut ends up like a cone. The tool is 100% moving perpendicular to the work using just the cross slide, but the cut is not perpendicular to the axis of rotation.
 

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