Author Topic: So, if your engine blew up...  (Read 3827 times)

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TWinOKC

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Reply #15 on: April 12, 2013, 10:58:25 pm
All Fireballs have alloy barrels on them.

I had wondered about that.  So aluminum alloy barrels with a steel sleeve?  All modern motorcycles are the same, including UCE's & Triumph?
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ace.cafe

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Reply #16 on: April 12, 2013, 11:55:59 pm
I had wondered about that.  So aluminum alloy barrels with a steel sleeve?  All modern motorcycles are the same, including UCE's & Triumph?

Yes, these are aluminum with an iron sleeve.
UCE barrels are too. I don't know about the modern Triumphs.

However, many of the modern bikes use an alloy barrel without the iron sleeve, and just coat the aluminum with a nickel-silicon-carbide plating inside, which is wear-resistant enough to last a long time in that role. This is especially common in dirt bikes.
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Arizoni

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Reply #17 on: April 13, 2013, 12:03:05 am
Ace
Without knowing the exact type of cast iron the old iron barrels are made from I can't say what the coef of thermal expansion is but here's a few data points:

Gray Cast Iron per ASTM A-48 = 6.0 X 10e-6 in/in/deg F.
"         "      "   per ASTM A-436 = 6.6 X 10e-6 in/in/deg F.

Ductile or nodular cast irons = 6.6 X 10e-6 in/in/deg F.

Malleable cast iron = 7.5 X 10e-6 in/in/deg F.

The only wrought steel I have any data on is 4340.
It's coef of thermal expansion at 400 degrees is 7.4 X 10e-6 in/in/deg F.

Taking the worst case situation between these values shows a difference of 7.4-6.0=1.4 X10e-6 in/in/deg F. so with a bore of 87mm (3.425 in) the expected bore expansion at 400 degrees F would be .049mm (.0019) less in cast iron.

Needless to say, if you have more reliable numbers for the materials involved use them.
If you don't, be sure to check my math before making any chips. :)

While I was typing all of this, you posted saying you are using a iron sleeve.
If it is malleable iron, notice that its coef of therm expansion is about the same as the 4340. :)
Jim
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ace.cafe

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Reply #18 on: April 13, 2013, 01:00:45 am
Ace
Without knowing the exact type of cast iron the old iron barrels are made from I can't say what the coef of thermal expansion is but here's a few data points:

Gray Cast Iron per ASTM A-48 = 6.0 X 10e-6 in/in/deg F.
"         "      "   per ASTM A-436 = 6.6 X 10e-6 in/in/deg F.

Ductile or nodular cast irons = 6.6 X 10e-6 in/in/deg F.

Malleable cast iron = 7.5 X 10e-6 in/in/deg F.

The only wrought steel I have any data on is 4340.
It's coef of thermal expansion at 400 degrees is 7.4 X 10e-6 in/in/deg F.

Taking the worst case situation between these values shows a difference of 7.4-6.0=1.4 X10e-6 in/in/deg F. so with a bore of 87mm (3.425 in) the expected bore expansion at 400 degrees F would be .049mm (.0019) less in cast iron.

Needless to say, if you have more reliable numbers for the materials involved use them.
If you don't, be sure to check my math before making any chips. :)

While I was typing all of this, you posted saying you are using a iron sleeve.
If it is malleable iron, notice that its coef of therm expansion is about the same as the 4340. :)

Thanks for the info!

God knows what it is? The barrels come from India.
We started out with putting them and the pistons in the oven and measuring.
Then we refined that over the years of using them, and collecting info from others.
We now have the data for making a very good clearance which works with our pistons and these barrels, and all the Fireballs are done the same.
This was a big part of solving the seizure problems, which we knew we had to do.
« Last Edit: April 13, 2013, 01:04:45 am by ace.cafe »
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Arizoni

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Reply #19 on: April 13, 2013, 01:34:17 am
I'm sure your data for the existing iron sleeved aluminum cylinders is very accurate but I was thinking about any changes in fit that would be needed if someone was wanting to use your new 535 piston in a rebored iron barrel cylinder.

I suppose the safest way to know what the old iron barrel cylinder is doing would be to measure its bore and then throw it into a 400 degree F oven.
A remeasurement of the bore at that temperature would tell you exactly what its expansion is and you could compare that with your data for the iron/aluminum cylinders.

If any change in room temperature fit was needed, using that method would tell you exactly how much to lap the bore for a easy break in.
Jim
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1999 Miata 10th Anniversary


Ice

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Reply #20 on: April 13, 2013, 02:01:38 am
 The only conditions in which I would find an iron barrel preferable to an alloy barrel would be in arctic environments.

 We are all acutely aware of the plight of the piston and rings but often forget the valves, the seats and the guides. Those poor things take a thermal beating.

 The more readily unwanted heat can be ejected from the barrel the less that heat will be transferred to the head and the longer it will last as well.
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ace.cafe

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Reply #21 on: April 13, 2013, 02:06:58 am
I'm sure your data for the existing iron sleeved aluminum cylinders is very accurate but I was thinking about any changes in fit that would be needed if someone was wanting to use your new 535 piston in a rebored iron barrel cylinder.

I suppose the safest way to know what the old iron barrel cylinder is doing would be to measure its bore and then throw it into a 400 degree F oven.
A remeasurement of the bore at that temperature would tell you exactly what its expansion is and you could compare that with your data for the iron/aluminum cylinders.

If any change in room temperature fit was needed, using that method would tell you exactly how much to lap the bore for a easy break in.

Yes, that's the way.
However, it gets tricky because the piston heats up and expands a lot faster and tends to want to nip up. It's important for the owner to lay off the throttle until the stuff all comes up to temp.
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