Broken Wings

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I found a couple cylinder liners for the OS FS-90 engine and not being able to leave well enough alone I figured I'd chrome plate the inside bore.

The company I work for does hard chrome plating on rifle barrel bores and my boss is an old gear head and when asked if he would do them for me he said sure, bring them in...

I'll either ruin two perfectly good liners or have a chrome lined OS FS-90 engine. (Eat your heart out Saito....)

I also found an ignition system for it and I've got all the parts to do the conversion to run a spark ignition as well.

While I'm there I'm going to test the hardness of one of the liners just to see what I've got. I can also use all the "good tools" to take measurements before and after.

I found an extra ring made by a guy in England named Gavin Carter, these rings are "Turned from fine grained Meehanite cast iron bar, Piston ring blank is then split and gapped, Ring is heat treated to relieve stress and set the uncompressed ring gap, they are then lapped to the correct thickness and finally turned and lapped to the finished bore size for a perfect fit."

I can check the ring gap before and after chrome.

Anyway, I hope to make this a kind of "Build Thread" for the glow engine section...

Hobbsy

My Feedback: (102)

Here's what a Saito 1.50 chrome bore looks like after 20 years, I guess it will be a long time before a comparo can happen. Keep us posted, I'm interested. You can see the piston ring start and stop marks and even slightly see where the ring gap was but there is nothing to feel or measure.

Broken Wings

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It should be fun to watch....

I found this concerning ring gap. Example: 4" (bore) x .0035 = .0 14 minimum gap.

I measured the bore with a caliper and got 1.089 inches, I'll really measure them tomorrow...

1.089 x .0035 = .0038 inches ring gap. A strand of hair from my head measured .002 inches.

I've got some Saito parts on this engine. Take note of the cool fuel filter with the real glass bowl...

bogbeagle

I think it was MAN, in the 60s, that experimented with chrome bores on one of their marine diesels.

They found that the pistons and rings wore out very quickly ... puzzling. It turned out that the surface finish was so good that no lubricant was being retained on the walls of the cylinders.

So, they used a shot-blast process prior to chrome-plating. This created tiny cavities which retained lube oil and solved the problem.

SrTelemaster150

Ahhhhh, most Saitos are AAC, Aluminum piston, Aluminum bore, Chrome plated bore. the ones that aren't are ABC Aluminum piston, Brass cylinder liner, Chrome plated bore.

So what's to eat my heart out over?

Hobbsy

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John was just being fascitious.

Broken Wings

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Ahhhhh, I'm about to chrome the bore on this OS engine.....get-it

Hobbsy

My Feedback: (102)

SR, when you're a Saito regular around here you can expect a zinger across your bow every now and then, in the spirit of fun of course.

SrTelemaster150

You mean they don't COME THAT WAY?

Broken Wings

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.... I may just ruin a perfectly good model engine.

earlwb

I don't think you'll ruin them. But it is a pretty neat thing to do for sure.
Are you going to hone the cylinders slightly after having them chromed? Or is your process good enough to leave them nicely done on the inside?

blw

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The Saito?

Broken Wings

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They should be good to go once they come out of the chrome tank.

Sport_Pilot

You need to hone out thy cylinder before you chrome it.  Just so the diameter is the same after chroming. 

Before you do, c heck to make sure the cylinder is not nitrided.  If it is it is acually harder than chrome.  Saito does chroming  to save weight with aluminum sleeves.  Not because it is the hardest surface to use.

I doubt OS uses nitrided cylinders as OS tends to wear out a bit quicker than some.

Broken Wings

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I'm NOT going to hone it before I chrome it, it's factory new and I'm sure I can't make it any better than what it is. I measured it and it's round 1.0904" within .0001" and has a .0004" taper. There isn't going to be that much chrome on the bore to make a difference. .00025" total. Remember, this is hard chrome, it doesn't take much. I'm not trying to build up a liner inside the liner.

I checked the hardness and its off scale, it measured an 8 HRC on the Rockwell "C" scale... Not very hard.

I'll get them back tomorrow and post some pictures of the results.

I did make a "fake" steel engine case or sleeve that the liner(s) slips into that will keep the plating off of the outside diameter of the liner. It also holds the liner in the tank so the anode can be placed inside the liner,inside the tank.

I also made a Delrin plug that allows the liner to be pushed out of the sleeve.

Once I get them back, I'll install the ring and check the end gap using a Vector Micro-View, its a video microscope measuring system. If I get .0038"minimum gap. I'm calling it good to go.

jeffie8696

Wings buddy I envy you.

Broken Wings

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Here are the cylinders back from the chrome tank. They came out Gorgeous.....

The surface is very smooth and uniform. I installed the ring and checked the end gap at the top of the cylinder and came up with .0046" at the cylinder wall and about .006 at the inner diameter of the ring. there's a slight angle where he split the ring when he made it. I checked out the ring under the microscope and its really nicely made.

The first picture is without and the other two are chromed. top and bottom. My little sleeve worked perfect, as the is no chrome on the outside of the liner so it should go back into the case like its supposed to.

earlwb

Those look nice. I think it turned out great.

Broken Wings

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It's not over yet, there's more to come...

jeffie8696

So you did this just to tease us? Are you going to be able to do it for a small fee for the rest of us Buuuuuuuuuuuuudy?

Broken Wings

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Do you have an FS-90?

SrTelemaster150

So, the FS 90 comes W/a non-chrome plated steel liner from the factory?

Broken Wings

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That is correct.

SrTelemaster150

Just curious as to what the engine life is W/O chrome plated bores?

Hobbsy

My Feedback: (102)

Hey John, mine is shinier.

Those look great waht is the next step in the process.