Author Topic: McDonald Imperial Super Diesel Crude Oil Engine  (Read 2729 times)

oldgoat

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Re: McDonald Imperial Super Diesel Crude Oil Engine
« Reply #45 on: July 27, 2020, 06:02:07 AM »
You will only get blowback if the needle and seat are leaky or the injector adjustment is incorrect.

cobbadog

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Re: McDonald Imperial Super Diesel Crude Oil Engine
« Reply #46 on: July 27, 2020, 12:28:59 PM »
YEs that is right but it can happen so I built this bomb proof model
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cobbadog

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Re: McDonald Imperial Super Diesel Crude Oil Engine
« Reply #47 on: July 27, 2020, 12:33:11 PM »
Hi Mike,
As oldgoat mentioned the cause of the blow back is a poorly seating needle. Fuel is gravity fed to the Hyvid Brons injector and pressure is a very simple plunger inside that has a spring inside to help seal the needle. If blow back happens it all ends up back at the tank which for my tank the worse that can happen is the lid will lift off.
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cobbadog

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Re: McDonald Imperial Super Diesel Crude Oil Engine
« Reply #48 on: August 06, 2020, 12:43:08 PM »
Today I got some play time and found an issue. Again I wiped out the bore and sprayed some Lanox inside and fitted the piston with no rings. I have a cylinder that is narrow in the middle of the stroke. Fromt between 45mm down from the top to 125mm down the piston sticks. But, if I rotate the piston 90' it does not. This may indicate an oval piston so I now have the piston in the chuck of the lathe and checking it with the dial indicator to see what is at fault.
I think that all that rust around the cylinder has swollen up and distorted the bore.
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glort

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Re: McDonald Imperial Super Diesel Crude Oil Engine
« Reply #49 on: August 07, 2020, 04:41:25 AM »

I thought pistons were SUPPOSED to be oval??

cobbadog

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Re: McDonald Imperial Super Diesel Crude Oil Engine
« Reply #50 on: August 07, 2020, 12:04:04 PM »
Not this one, fairly certain it is the bore that is distorted.
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cobbadog

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Re: McDonald Imperial Super Diesel Crude Oil Engine
« Reply #51 on: August 10, 2020, 06:53:39 AM »
Going to be attacking the bore with a large hone soon and today the head came back with the new valve guides fitted and reamed, new stainless steel valves machined to suit and the seats re-made so at least this is ready to be fitted after the bore and piston are in.
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cobbadog

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Re: McDonald Imperial Super Diesel Crude Oil Engine
« Reply #52 on: August 12, 2020, 07:02:08 AM »
Here is the head ready to fit some springs but I have to drill the valve stems to fit a pin to hold the cups in place that hold the springs under tension. I do not have the original horseshoe clips so a couple of pins will work well.
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cobbadog

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Re: McDonald Imperial Super Diesel Crude Oil Engine
« Reply #53 on: September 05, 2020, 06:50:33 AM »
At last I got back to this project this afternoon. I have borrow a large honer and it certainly has cleaned up the rusty surface very well but after a fairly long time I still cannot get the piston with no rings to slide up the bore. The top goes in with no problems but the further I slide it the tighter it gets and will only slide in as far as the bottom of the piston skirt.
This got me thinking, yep hard to believe, that maybe the piston is out of shape and not the bore as I was thinking. I had the piston off the conrod and put it in the lathe and using a dial indicator got some out of round numbers on the OD of the piston but from top to bottom it changed a lot and was messing me up.
So I engaged the grey matter again and used my digit calipers to measure the OD as far as it could reach over the skirt measuring from the side. and did this at 3 different points, top, middle and bottom.
Not sure if my calipers reached over the complete OD of the piston but with the calipers pushed all the way on then closed the gap and locked the calipers it gave the following readings.
Top -      87.77mm
Middle -  88.21mm
Bottom - 88.40mm
This meant that the piston got wider the further down I measured it and by a total of 0.63mm and this to me would indicate that the piston and not the bore is at fault.
Happy to hear any and all comments on this tricky bastard.
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mikenash

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Re: McDonald Imperial Super Diesel Crude Oil Engine
« Reply #54 on: September 05, 2020, 01:14:54 PM »
Y’know, if the piston is most of a mm different in diameter from place to place - it seems to me that if you held a straight-edge along it in various places there would be enough for the straight-edge to “rock” visibly?  Cheers

cobbadog

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Re: McDonald Imperial Super Diesel Crude Oil Engine
« Reply #55 on: September 05, 2020, 01:47:58 PM »
Cheers Mike, the taper is on the piston itself and not the bore. I have no way of measuring the bore but was told to use a length of stiff fencing wire cut to size and use it as a gauge. Tomorrow I will know ,ore, I hope.
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cobbadog

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Re: McDonald Imperial Super Diesel Crude Oil Engine
« Reply #56 on: September 19, 2020, 06:56:29 AM »
Back to the Mac and trying to sort what exactly is out of round. The piston is 0.009" out of round for certain and after putting on some "blue" and fitting the piston into the bore to see what part rubbed it hits the bore both top and bottom.
You can see on the skirt of the piston where the 'blue' is untouched and where it is rubbed smooth. What clearance should there be between the bore and piston on a 3.500" bore?
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cobbadog

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Re: McDonald Imperial Super Diesel Crude Oil Engine
« Reply #57 on: September 20, 2020, 07:40:17 AM »
And the winner is.....cobbadog! I got the bastard!
There was definitely 2 different issues, the bore for what ever reason was undersized at the bottom end and believe or not there was a bump on the piston skirt. So with a long time honing, washing it out and then checking it was time to go to the lathe.
As suggested I set it up using the dial indicator and this time with the piston top in the chuck and at that point it ran true. As I went down the skirt things were good but then I rotated the chuck and presto a lump on the skirt. So no amount of honing would fix this issue and would make the bore completely the wrong size if I didn't machine the piston. So yes something must have been dropped onto it and caused this problem. Now I have the same clearance top and bottom and that is 0.010".
In the pics you can see the hone in position ready to have the drill connected to it which is a socket on an extension with a slot to engage the small lugs to drive it around. Liberal amounts of kero was used and it certainly hooked into cleaning things up and it works far better than the spring loaded hones.
You can see the high spot on the skirt and as I took 0.01mm off at a time it slowly progressed towards the oil ring land then from there up all was good.
A picture of the Australian made Somers brand rigid hone.
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cobbadog

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Re: McDonald Imperial Super Diesel Crude Oil Engine
« Reply #58 on: September 21, 2020, 07:42:22 AM »
Got the rings onto the piston and gapped them using the cut off wheel of my grinder. (that will be a talking point).
Fitted the piston then the crank into place and connected the big end to the conrod and then to the crank. Made a new gasket out of 1.5mm paper for the side cover that houses the other crank main, fitted a new oil seal and then put the cover on and tightened it. The rings a have a good hold of the bore but once I have it moving I can move it with a struggle by turning the crank by hand. Once the flywheels are on it will be a lot easier.
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glort

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Re: McDonald Imperial Super Diesel Crude Oil Engine
« Reply #59 on: September 21, 2020, 11:54:40 AM »

Can't wait to see the full feature length movie of it's first Fire up!

Going to be still chugging along long after I'm gone and probably better than it left the factory.