Japanman

Hi all,
I have been pondering conrod bushing materials. Have any of you had experience with cox big ends wearing out? I haven`t and I have had experience with bronze bushed rod bigends wearing and of course aluminium rods wearing. In both cases they seem to wear the crankpin- but my coxes never seemed to get wear in either the crank or rod- i guess from hard steel on hard steel burnishing has very little friction- go try it for your self.
That said, what IS the rod material for a cox 049? (calling A.J.C... Dickey bird... etc etc)

Someone mentioned a taipan egine running a steel bush and it has got me thinking.

J.M

XJet

I'm pretty sure the Cox rods are steel -- but I haven't tested one.

I don't like aluminum as a bearing material -- it galls easily and has a high rate of wear.

However, for very small (1/2A) engines, bushing a conrod's big-end with *anything* might not be that easy.

You'll have to add meat to the bottom of the rod to allow for the bushing itself (and in some engines -- like the Cox) there's not really any room to do that without hitting the crankcase.

If you don't leave enough meat in the rod itself then you'll find them breaking very quickly.

The other thing to watch is that aluminum has a higher COTE (coefficient of thermal expansion) than bronze or steel, which means that bushing will need to be a very snug interference fit if you're to avoid the rod expanding away and slipping on the bushing itself.

I haven't looked at the Norvel, but if the rods on them break as easily as some people seem to think, such a mod might be worthwhile -- although perhaps a better option would be to hard-anodize the inside of the big end rather than bush it. Another option would be to use ENP to put a layer of slipery nickel in that area.

If I even break a rod I'll try both of those options.

Tim Wiltse-RCU

J.M.,

The rod in a Cox .049 is good ol' LedLoy Steel just like the cylinders and pistons! I hope this helps.


Later,
Tim

Japanman

Xjet,
I am making a new rod from a bit of 2024 I have- so 'meat' isn`t a problem. The press fit may take a bit of experimentantion.. The bore is so small that the %interference is going to make for a small figure.
norvels have no bushing other than the rod material it`s self.

I also don`t like aluminium as a bushing material particularly where highish loads are incountered like in a rod big end.

Tim

Is it really? it seems harder than the cylinder material... my precision hardness test (performed by Dr cheapfiale) seems to indicate the rod is hardend

Tim Wiltse-RCU

J.M.,


It very well might be hardened...it only makes sence. But it is listed as LedLoy Steel.


Later,
Tim

ZAGNUT

My Feedback: (1)

look at the pic below...notice the little stamped marks around the bushing. this bushing was staked in place and will NEVER spin in the rod.

also i've got a couple of the cox pistons with the aluminium rod and even though these are well used (judging by the loose fit in any cylinder) the rod's big end is still a close fit on the crankpin. Xjet's idea of using electroless nickel also sounds good..easy too. would also make a good treatment for backplates, IMO this is the #1 source of the plug killing alum particles.


dave

Japanman

Zagnut,
Thanks for the picture- thats a great idea- there is nothing like a physical barrier to things comming appart- I might try burnishing over a lip if I can, ala some jewellery stone settings. That way there is less chance of a stress raising point put in by accident.

J.M

gcb

Only one .049 had a bushed lower conrod that I can remember. The O&R .049 had a bronze "eyelet" type insert on the lower end that was replaceable.

George

Japanman

Xjet
The more I think about your Idea of E.N on the rod the more I like it- How much of a layer do you think you can build up? is 0.05mm feasable?
I have a piston and rod assembly that is not separateble- are there any corrosive fumes emmitted that would attack the piston if left out of the solution with the lower half of the rod immersed?

J.M

XJet

0.05mm (2 thou) is achievable -- but it's a slow process so would take some time to reach this level and, to be quite honest, you'll get just as much benefit from a much thinner coating so I wouldn't bother going to that extreme.

The fumes aren't particularly corrosive (basically just steam that evaporates off the hot ENP solution) so that's not a problem. If you were concerned however, you could use something like CRC Soft-Seal to protect the rest of the component from exposure. This stuff washes off with any petroleum solvent and I use it a lot for rust-protection on my steel stock.

The *excellent* thing about ENS is that the layer produced is slightly porus which means that, as well as being very slipery in the first place, it will also absorb small amounts of oil from the fuel to provide extra protection against galling or lube-film breakdown.

You want to use a high-phosphorus solution so as to get a "hard" plating rather than a "decorative" and more ductile one.

I use ENP quite a bit in my workshop and have even protected high-temperature gas-nozzles with it. After several hours running at temperatures of over 800 deg C, the plating remains intact and unoxidized.

Some base materials (such as copper and zinc) require a pre-plating treatment before the nickel can be applied so I'll have to check and make sure no similar treatment is required for the high-zinc aluminum alloys (7075) or the high-copper ones (2024).

Japanman

Xjet,
Thanks for the information... The only reason I was thinking of a thickish layer was longevity-

In the interim I have been thinking about other areas of the engine that could benifit from a hard plating.. and the crankcase bushing area is pretty high on that list! Running a pipe seems to place a considerably higher load on the rod big end and the crankshaft/crankcase. In my norvel .061 running on the pipe caused both of these parts to wear- particularly the crankcase. I guess that a hard nickel coating put in both of these places would yeild an increase in power reaching the prop/fan without the weight penalty of bearings (but maybe not as much of a decrease in friction as ballbearings...?) and should halt wear so seem highly attractive to me.
Of course in both cases the I.D would need to be taken out by a small amount to compensate for the layer and possibly need honing afterwards...

Is it possible to use a coating (e.g for the crankcase) to mask areas where plating isn`t required?

You sound like you have all the gear, would you consider plating a couple of rod bigends and maybe a crankcase (crankshaft bore)?

J.M

ajcoholic

My Feedback: (10)

I have nickel plated things like rotary valves and such and allthough I am set up for hard chrome, nickel and electro-less nickel plating (bought the stuff a few winters ago and just havent had time to get into it other than a few things like rechroming a trailer hitch ball and a few engine parts..) and I found in an hour the plating was between 1 and 2 thou thick. I did lap afterwards with a diamond charged aluminum lap.

Its certainly one way to approach the problem I think...

AJC

XJet

When I went out to get some chrome/nickel electroplating materials I found that here in (clean/green) New Zealand, acquiring such chemicals requires that one sells ones children into slavery, give 12 pints of blood, sign a pact with the devil and prove that you are not a terrorist bent on poisoning a city's water with the lethal cocktails required.

The compliance costs associated with setting up even a tiny electroplating tank for chrome or nickel was measured in thousands of dollars!

Bah! What's the world coming to?

When I was a kid I made nitroglycerine, built mortars and rockets out of steam-pipe, made a great flame-thrower that spat an inferno over 20 yards, built my own guns and did a whole lot more. These days I'm surprised that you don't have to have a background check to buy a Nerf gun or to play with sharp objects :-(

Japanman

Err.. come to Japan then... It make N.Z seem like the land of freedoms... I found a place to buy nitro here and it was about US$70 per 500ml!!
And I won`t even mention me trying to buy aluminium... you just wouldn`t believe it.

J.M

ajcoholic

My Feedback: (10)

I bought all my plating supplies from Caswell's over the internet (we have a dealer here in Canada) and it came with a host of precautions especially the chrome plating gear. But they also give the proper chemicals to mix into the solutions after when you want to dispose of it, and the stuff is supposed to become fairly benign... I am very carefull though when working with the tanks and such as I am not too crazy about getting the stuff on my skin or breathing the fumes! I do set up my tanks in my paint spray booth and vent everything outdoors.

AJC

Japanman

I found the caswell site, but I do not know about the difference between hard nickel and lets say pure nickel plate...
I found one site with a bit of info though.

1. Phosphorus content between 3 and 7%. These coatings have excellent high wear resistance. Excellent corrosion resistance in concentrated caustic soda.

2. Phosphorus content between 9 and 12%. Corrosion protection and abrasion resistance are good enough for most applications. The plating bath works particularly economically.

3. Phosphorus content between 10 and 13%. The coatings are very ductile and corrosion resistant. They fulfil the highest demands for corrosion resistance against chlorides and simultaneous mechanical stress.

A.J, does the caswell stuff tell you what percent phosphorus etc?

I emailed them a while ago but got no reply.

J.M

ajcoholic

My Feedback: (10)

Its been about 3 years since I bought the supplies and 2 since I mixed up the solutions and tried them out. I did some nickel plate this winter on some parts but I dont recall seeing any specs other than the plate of nickel in the bath is supposed to be 100% pure nickel.

I would have to check in the manual...

AJC

XJet

He's probably talking about the elecroless nickel solution, not the electroplating solution.

Japanman

Yes,I was talking about the electroless type.

Have either of you tried plating cox cylinders? seems like it would be a good idea to me, the piston is already quite a bit harder than most aluminiums, might make for a very long lasting cylinder.

Xjet, did you get an electroless nickel setup? If so, from where?

J.M

ajcoholic

My Feedback: (10)

I have both nickel setups. I eventually want to get into chrome plating pistons and cylinders (not both in the same engine ) but neve had the time to really work at it.

AJC

ZAGNUT

My Feedback: (1)

have a look at this site [link]http://hometown.aol.com/nivirt/Chroming.html[/link]

also checkout his homepage, lots of 1/2A engine building info


dave

XJet

I just rolled up to a local plating shop that offered electroless nickel as one of the services they offered and asked them if I could buy some of the chemicals.

They were reluctant at first, claiming that it was a complex process involving careful temperature and pH monitoring -- but I told them that this wasn't a problem from my perspective and assured them that I was happy to accept the results of my own incompetence and inexperience.

For US$20 I got two gallons of solution and a 200ml of buffer and "replenisher" solutions.

That was two years ago and I've used only about a third of that with *excellent* results.

Keeping the pH in balance is pretty easy (use amonia or the buffer to adjust down/up) and so long as your workpiece is nice and clean, and you keep the temperature within the specified range, it works like a charm.

Japanman

I am suprised they sold you the stuff, my experience with those sort of places is they can be a bit cagey.

J.M