Reducing Friction

Quite right Del...

I had a Puch motorbike way back, and its cylinder was chrome plated to reduce friction, but to hold the oil the chrome plating had numerous small 'spots' which weren't chromed in it purely to hold the oil.

John.

Good reply, Del! I suspect that the reduction of the metal that the piston sees on the wall (tops of the crosshatched metal) will also reduce friction.

Slick 50 still around? I havn't heard of it for quite a while, I used to use the Slick 50 grease in my CV joints in my race buggy, only time I ever had to change a CV (that was still driving mind you) was after I got some sand in the jont and 1-2 of the balls had turned to nice diamond shape with bits of the hardening falling out of the CV boot hole

Slick 50 has been wonderful for me - I had a Saab with the Triumph engine get run dry of water - When I fixed the radiator and checked compression it was all +- 5 pounds-

and ran like a top for another 60,00 miles -

rcb

If you are using Slick 50 and Castrol, then you need to try Schaeffer products. The only product that comes close to the same performance as Schaeffer is Royal Purple

You should gain about 5 hp over the Castrol/Slick 50 combination.

Thanks for the good information.

With your experience, perhaps you can tell if there is a difference in the cylinder wear on the side the piston is leaning on due to the connecting rod slope versus the opposite side the piston leans on during the upstroke with much lighter load, or is the wear even all around the cylinder walls?

Having even wear all around would be caused by the rings, having much more wear on one side would be caused by the piston side force.

In other words, what causes more wear, the rings or the piston? Do you have any observation on that? Thanks.

Hmm- 30 years ago - rebuilding Aircraft engines - I think I might remember having discussed that - but I do NOT remember any thing useful -

Given an opportunity - look at the drag / scuff marks on the skirt - and that will probably be the quick indicator.

If you know someone rebuilding Wright Radials - that should give a one stop place to test -

You can still get those from Military Surplus now and then - if you are THAT interested :)

rcb

Testing - Testing - Testing

The rings take the brunt of the ware, the 'slope' as you put it does mean the piston skirt wears on the front and back slightly asymetrically and yes the bore will wear slighty oval...eventually...(I theenk).

Del

The rings....cause the most ware.

There should be about .015 clearance between piston and cylinder wall at the skirt. ring gap is around .020 inch. Check the exact spec is always advisable when checking ring gap

Rings being like springs are in contact with the cylinder wall usually 2 compression and 1 oil scraper (three pieces with 2 very thin rings on each side of the ring land)

If I am going into and engine due rod-bearing failure or valve problems, I expect to see even ware on the piston skirts usually below the wrist pins. The top of the piston above the top compression ring will be where I expect to see the most un even ware due to uneven carbon build up.

If a piston is rocking in the cylinder on the up or down stroke, there is to much ware in the Cly wall. I would set a ring in the cylinder, measure the ring gap, if out of spec. Bore the Cly and new pistons to fit. Fitting each ring to each cylinder as well.

Lots of time setting this up will equal lots of good miles after its done.

That is why good lubrication is so important, to take up the clearance between cylinder and piston evenly. There is no way to remove friction absolutely, we can at best reduce it significantly

Hi Guys, As an old piston engine aircraft mechanic I'm familiar with this. Your memory is correct. That crosshatch pattern plays a big part in what "breaking-in" a new or overhauled engine is all about. Those fine scratches increase friction at first, allowing for faster seating of the face of the rings. Those scratches also hold oil to lubricate and remove the extra heat from the rings and cylinder walls as they wear in to a working fit. This goes on for the break-in period with resulting higher oil consumption and cylinder head temperature. Now...the engine is broke-in and friction is reduced. I've watched it happen many times. Flying along, scan the engine gauges and notice cylinder head temperature has suddenly dropped. Land, and when checking oil it's fine instead of needing some.

As already said, you need some "voids" to keep the lubricant. All surfaces manufactured by any process, have a roughness profile (higher or lower depending on the manufacturing process and variables of such process).

One of the hybrid parameters used to measure/compare the roughness grade is the material ratio curve or Abbot-Firestone curve. This represents the percentage of surface at a every level between the highest peak and the lowest valley (profile height) This curve has a shape similar to that I will try to include. The first quickly decreasing portion of curve represents the amount of material that will be worn at the first phases of contact, because there is a few surface to withstand the loads. Then there is a slightly decreasing portion, nearly horizontal and longer that means the normal useful life of the part, being worn slowly because more surface is available to distribute the loads, so stresses are lower. The final portion of the curve which represents the deeper valleys portion is the "reservoir" for lubricant.

Best regards

Deep Cryogenic Processing of automotive parts, especially hi performance can significantly improve the material.

All great responses. I was trying to think of a way though to reduce the friction between a light weight metal like aluminum and a plastic. Would a crosshatch pattern be the way to go without damaging the plastic material? My mind set was thinking reducing the surface to surface contact of the two parts.

Would a crosshatch pattern be the way to go without damaging the plastic material?

No..no..no..no...no.

The answer would be to choose the correct plastic, many are 'self lubricating'.
Nylon is a good cheap engineering plastic which has this property.

The second thing is to design the bearing surface correctly...

Del

(PS I reserve the right to be wrong on this...cos I'm a cat)

For Aluminum, try a Teflon-impregnated Hard Anodize. The source below "Nituff" is a coating .002 inch thick (.001 inch buildup). It produces an "Orange Peel" surface, which works well for retaining lubricant (or you can run it dry).

http://www.nimet.com/exclusive.php?process=nituff