Cylinder Plating

[jflies]

Hi guys,

I have a model airplane engine that is dear to me, but it is suffering from a peeling cylinder liner. These engines have a removable liner that is typically nickel plated, but sometimes chrome is used instead.

Parts for the engine are impossible to come by, and my only option is to re-plate the cylinder bore with either nickel or chrome. I'm fairly handy, been doing some light machining now for several years in my spare time... Is hard-chroming or hard-nickel plating something that is possible with a "home plating kit"?

Also, if any of you have experience with plating cylinder bores, could I convince you (with a cash reward of course) to possibly do this for me if I shipped you the liner?

Thanks so much!!!

 

[petertha]

Maybe you could appeal to some of the few remaining non-big engine builders of racing fame? I doubt they chrome themselves in-house, think they job it out. But maybe could integrate liner in their batch, or at least let you know what's involved? From what I read, chroming is one thing, lapping it into condition is yet another.

Dub Jett
http://www.jettengineering.com/

used to be Henry Nelson, now
http://aeroracingengines.com/

potentially this person (or at least check out his related posts, its fascinating reading)
http://www.modelenginemaker.com/index.php?topic=3890.0

 

[Cogsy]

I know many 2 stroke motocross style bikes used plated cylinders and having them replated is a fairly cheap job (maybe $50-80 here in Aus), so you might want to take it to a motocycle repair shop and see what they can offer.

 

[XD351]

It is possible but you would need to weigh up the cost of setting up your plating tank , power supply (constant current )and heating the solution to 120F for hardchrome then finding a good book on the theory and practice of electroplating as it is a little more complicated than just dunking the part into the solution and switching the power on .
There are small differences in procedure for steel , cast iron and brass mainly to do with cleaning and how long you reverse etch them for if at all (reverse the polarity of the power supply ) ie steel if i remember correctly(and it has been a long time since i worked in a plating shop) was around 20 seconds .
You still need to determine what the bore is plated with - Hydrochloric Acid turns green on Chrome from memory and Nickel does nothing.
Stripping the old stuff off is the next issue - For Chrome we used caustic solution and a small current to etch it off but brass was a real pain as caustic wanted to eat it away .
I'm assuming this engine has a lapped piston liner set ? if so you could have a real job on your hands getting that lapped fit back .
I think your best bet is to try and find a Hardchrome plating shop ( not one that does the shiny stuff as it is different ) and talk to them or may be a trade college / school as the teachers may be able to point you in the right direction .
Don't expect it to be cheap as small stuff can be really time consuming .

Ian

 

[digiex-chris]

Replacing the liner with a cast iron one might be a way to go. Taper lapping is a little fiddly but not too bad. I've done it on an OS .46LA keeping the original pistons and actually gained performance by beating the factory tolerances. This was back before I had a milling machine too, I cut the ports on the lathe by using change gears to index the spindle and making an auxilery spindle to hold an endmill.

 

[jflies]

The engine in question is has a nickel plated brass liner, and an aluminum piston. I'm not too keen on machining a whole new cylinder liner as I don't think I could get the tolerances close enough on the cheap machines I have access to. I know there used to be people who could do a fantastic job replating the liners with hard chrome after honing out the old nickel. I'm sure it was quite involved, but these people did it in their small home workshops/garages, so I'm sure it's possible. I've finally found one person who can do this for me, but just for fun I would love to try replating some old garbage cylinder liners.

 

[digiex-chris]

The nice thing about the tolerances involved in making liners on the home shop scale is it's actually not a machine process, but rather a check and adjust by hand one. The quality or size of your machine doesn't matter much. If you can stop the bore anywhere between 0.001" to 0.005" undersize, you're golden. Surface finish and accidental taper doesn't even matter. You take care of the rest of it with an expanding lap, passing it in and out of it a little at a time by hand till it's just right and test the fit of the piston in it. Don't even need to measure. I typically pull the liner right off the lathe, and hold it in my hand, and only use the lathe for spinning the lap for me. Aluminum piston in a cast iron bore actually makes a nice bearing surface after it's run in. It'd be a fantastic learning experience and good bragging rights!

I have heard of people plating nickel by hand quite easily with the Caswell system. [ame]https://www.youtube.com/watch?v=8lAzEw9zNVY[/ame]

I'm not sure how much hard chrome grows the surface but usually it's ground afterwards on critical parts. Might want to avoid that if you're not willing to lap it back to match the piston. Should be easily able to control nickel to a few ten thousandths but I'd still prefer going thick and lapping it in after.

Actually tolerances brings up another question that might be another consideration...if it's peeling, is it also worn?

 

[XD351]

We used to try and achieve .0007 to .001 inch deposit per hour and this left a finish that was smooth with no real pimples .
I know the model nitro engines in my model cars use chrome on brass and they put out 50k + rpm with no problems it only looks like a flash plating (.0001-.0002 inch deposit) .
Heavy deposits would be more prone to chipping or flaking and .005 deposit max .
Heavy deposits will also cause the cylinder to be barrel shaped as you tend to get a slightly heavier deposit at the ends and around sharp edges like ports etc but a flash plating as mentioned above should be ok and a touch up on a lap will fix it.
If you have some scrap cylinders and a sense of adventure then give it a go !
While i'm here i was thinking today about other coatings like titanium nitride and boron nitride and began to wonder how they would go for cylinder and crankshaft coatings or even if they could be applied to them in the home workshop - looks like i might have to do some homework on this !

Ian

 

[Swifty]

That home nickel plating kit works well, could be a very handy thing.

I just googled it, we have a local supplier here in Melbourne, electroless nickel may be the way to go. Here's a link for Aussies http://www.caswellplating.com.au/store/store.php/products/electroless-nickel-kit

Paul.

 

[Cogsy]

I have a home electroplating kit that can plate in gold, solver, copper, nickel and chrome but I doubt it would be any good for this purpose. It's really just a cosmetic coating and is very thin.

The plating on the bore of my MX bike is extremely hard and duarable. These bikes chew through rings (typically changed every 10-15 hours of use, or even more often for competitive racers) and the pistons are replaced every 3rd-4th ring change, yet the bores remain in pristine condition (barring engine blow-ups or running too lean, etc) for extended periods.

I would expect the plating from my home kit to wear off inside the first 10 minutes of operation in an engine.

I am going to look at blinging up some engine parts with it though!

 

[///]

Caswell does a Hard Chrome kit, the Aussie version is pricey tho, ~$400
The Aussie pricing used to be extreme compared to US Caswell, seems to be more reasonable these days.

 

[Blogwitch]

As with any job like this, either buffing or plating, it is the original surface finish that matters unless you go for a thick hard wearing coating.
With these small home plating kits, they really aren't designed to put extra thick coatings on that can be brought back to a good original finish, you will just remove the miniscule amount that was deposited if you try to lap it.
I used to have a hard nickel coating put onto parts that I had made for production machinery, and ANY flaws in the original surface were just brought up onto the new plated surface, in my case it was about 1 to 2 thou thick, it didn't really matter as where I needed the hard coating was actually only a tiny bearing area, but in your case, it surely would.
That is why cosmetic chrome plating is so expensive, it isn't the plating that costs, but the man hours required to get the original surface finish up to scratch.
BTW, all the shiny bits on say F1 cars are in fact nickel plated. They don't allow chrome plating on things such as springs etc, as it is a skin, so could cover up minute flaws, whereas bright nickel plating allows any flaws to show through.

John

 

[Swifty]

During my working life, we made a lot of special assembly machines for production lines, the base plates were nickel plated to prevent rust. These plates were fairly large, often 1200mm x 1600mm and 25mm thick, all tapped holes, dowell holes etc were finished before plating, the thickness of plating made no difference to sizes so it must have been very thin.

Paul.

 

[lohring]

A description of how an expert, Jim Allen, chrome plates cylinders can be found starting at the bottom of this page.

Lohring Miller