A new attempt at making piston rings

[petertha]

Most of Trimble math and calculations are beyond my ability to understand them but I am unsure if a slight deviation in dowel size is a problem as long as the mandrel diameter and the offset are adjusted accordingly. With the small dowel as calculated it is difficult to get a pin sized to the correct diameter. For instance in his 1" bore example the dowel is .150. 5/32 is .156 and is a standard rod size. Would using the oversized dowel be a problem as long as the mandrel and offset are adjusted accordingly? A 1 1/8 bore would give a dowel of .16875. Would a 5/32 diameter be too much variation?

The answer to your question is found by looking at how any T/B and D/B coordinates land relative to the plot. The only math is dividing two numbers. It might fall within the recommended guidance range, or it may push/exceed one or more of the boundaries. I happen to know that several commercial & operational rings land around the periphery of the 4 constraint curves, which I suppose is good news. To what degree, or how well they run, or reliability of measured dimensions is different discussion. But if you have to make rings from scratch & you accept the Trimble methodology, why not follow the recipe? Aim for the bullseye or consciously target an area that makes sense to your engine and/or skills?

To your second point (IMHO) if someone can produce the other 99% of a typical model engine up to and including the last but critically important bits: a finicky, thin section cast iron ring, a matching piston, both to +/- 0.0005" & appropriate finish, I just don't see how turning a 1" long straight dowel shaft to within 0.001" is a significant or time consuming challenge by comparison. The dowel seems easy by comparison. What is achieved by swapping in a different sized nominal 32nds stock at hand & making mandrel / spacing adjustments on the fly? This is just my own view but I accept there are many ways to get the job done.

 

[Steamchick]

I seriously doubt that.

Aye, got my powers of 10 wrong there. 20micron sound better? Just figured out when typing micron, as spell check changed it to mm. - typing 0. 0 2 mm was changed to 0.0002mm! Flipping smell checker again!
Thanks for spotting that one.
K2

 

[Brian Rupnow]

General Question--When you make rings, do you machine the outside diameter of the rings after they have been heat treated? I'm trying to get a handle on this. The Trimble method does have a final "Skimming" step where the o.d. of the rings is turned after the ring is heat treated. I believe that many people make rings quite successfully without this final machining operation.---Brian

 

[mayhugh1]

General Question--When you make rings, do you machine the outside diameter of the rings after they have been heat treated? I'm trying to get a handle on this. The Trimble method does have a final "Skimming" step where the o.d. of the rings is turned after the ring is heat treated. I believe that many people make rings quite successfully without this final machining operation.---Brian

The Trimble method doesn't use a turning operation after heat treatment. That's the whole point of his technique. You need to invest a few dollars in reprints of the original Strictly IC articles. - Terry

 

[Brian Rupnow]

Terry-I can't find out where to buy them. Do you have a link that will get me to wherever I can buy them?---Brian

 

[minh-thanh]

When i finish heating the ring i usually leave everything as is and put it on the lathe and clean the outside surface with sandpaper (that's one of the reasons i usually make the ring diameter bigger than the cylinder diameter 0, 3mm , although using sandpaper it changes very little ring diameter )
I only clean the surface because I like rings with "nice surface" , I haven't done that before but they are fine

 

[doc1955]

Nope and I have always used the process as described in The Shop Wisdom Of Philip Duclos.
And have never had much of a problem getting them to seat and give me good compression.


LOL maybe I've just been lucky lol

 

[Gordon]

Terry-I can't find out where to buy them. Do you have a link that will get me to wherever I can buy them?---Brian

http://www.strictlyic.com/pit01.htm

 

[Brian Rupnow]

Thanks Gordon--I've just sent off for the three magazine articles that cover Trimble's method of making rings in strictly I. C. Magazine in the USA.

 

[awake]

Can anybody sum up the Trimble method in a nutshell, and likewise for the Duclos or any other methods? I'm not talking about step-by-step comparison, but is there something in particular that characterizes and distinguishes each method?

 

[Brian Rupnow]

This video pretty well sums up the Philip Duclos method of ring making.---Brian

 

[DKGrimm]

Can anybody sum up the Trimble method in a nutshell, and likewise for the Duclos or any other methods? I'm not talking about step-by-step comparison, but is there something in particular that characterizes and distinguishes each method?

A quote attributed to Albert Einstein comes to mind: "Everything should be as simple as possible but not simpler."

I don't mean to be flippant about it, but I think there are a lot of similarities between the methods, but some critical differences in the details.

 

[petertha]

Just for interest, I manually altered the Trimble recommended T/B, D/B, W/B factors in order to force the resultant dimensions that Duclos showed for his OD (taken to be Bore), thickness, width & dowel pin (yellow spreadsheet cells). It then superimposes on the Trimble plot like so. Not sure if I'm interpreting correctly, but it doesn't exceed cast iron max operating stress, or max installation stress. But the ring would exert 'something' below 30 psi wall pressure. To what degree I cant say. The SIC article didn't provide underlying formulas or line gradations. So the ring would provide less sealing pressure during induction stroke on that basis & I believe less total sealing pressure under additive combustion pressure. Whether that is appropriate or acceptable to that engine is for others to speculate. The Duclos ring (axial) thickness at 0.036" is 0.014" thicker than Trimble's at 0.022". The article discusses his rationale which I wont reiterate. For comparison, last 2 screen grabs are same bore but using Trimble recommendations.

Notice that he cleaved the ring, he did not slit saw a gap. Its still not exactly apples to apples comparable to Trimble heat set jig which ensures the dowel contact is applied on the neutral axis. I'm pretty sure there is no valid way to similarly reverse plot a slit ring. Calculating the effect of a wider ring, yes, as long as it was cleaved.

 

[johwen]

Hi Brian,
I'm sorry I did not know you had no access to Trimble articles, so having a full copy of SIC I have copied all the article and put them on 2 PDFs for you.
Hope this helps you overcome your difficulties with the rings. Frances Washburn was suppling copies but the web site is not working so maybe she is no longer able to continue. If you have any questions give me a shout. Cheers John. These files are the basic Trimble method that I follow however the full Trimble description is more detailed in many issues. J.

EDIT: The "Strictly IC" article attachments had to be deleted as they are still under copyri8tht. The "Strictly IC" website is till active. The link to the back issue order form is:
http://www.strictlyic.com/b0_form.htmStaff HMEM

 

[johwen]

General Question--When you make rings, do you machine the outside diameter of the rings after they have been heat treated? I'm trying to get a handle on this. The Trimble method does have a final "Skimming" step where the o.d. of the rings is turned after the ring is heat treated. I believe that many people make rings quite successfully without this final machining operation.---Brian

Brian I just turn to size one thou cover bore size just a fine turn finish then Heat treat. The minute highs on the surface rub down and seat very quickly John

 

[Skipper]

This video pretty well sums up the Philip Duclos method of ring making.---Brian

Great video! What about RING GAP? When the piston and rings get hot the ring needs some gap for thermal expansion. WHAT DO YOU GUYS THINK?

 

[Skipper]

Hi Brian,
I'm sorry I did not know you had no access to Trimble articles, so having a full copy of SIC I have copied all the article and put them on 2 PDFs for you.
Hope this helps you overcome your difficulties with the rings. Frances Washburn was suppling copies but the web site is not working so maybe she is no longer able to continue. If you have any questions give me a shout. Cheers John. These files are the basic Trimble method that I follow however the full Trimble description is more detailed in many issues. J.

EDIT: The "Strictly IC" article attachments had to be deleted as they are still under copyri8tht. The "Strictly IC" website is till active. The link to the back issue order form is:
http://www.strictlyic.com/b0_form.htmStaff HMEM

Couldn’t open pdf file

 

[Skipper]

What about RING GAP FOR THERMAL EXPANSION ? 0.004.

 

[petertha]

Yes, I was looking for the Duclos (post heat treat) ring gap dimension too, didn't see that mentioned. Maybe its in the comments or another video but I didn't pursue.

And I think this illustrates the potential for likely inconsistencies of saying The Trimble Method or the The Duclos Method or The Brian Method.... There are at least a dozen or so input parameters that might indicate or define how a ring was made. So naming a method, or naming a method & omitting/altering/skipping mention of key parameters is only going to cause confusion for others down the line, seeking help & reading these posts. That's why I posted #271. And that's just discussing the ring. As others have mentioned, the ring, the bore, the piston equally factor into things.

I'm no expert in this stuff but that's really what motivated me to make a spreadsheet. Its not necessary but helps me digest & visualize things. Its too bad Trimble didn't release the underlying 'source code' & inquisitive minds today could evaluate it on its engineering basis. But I wonder how many actually would & unfortunately he is no longer around to weigh in. The SIC article (pg-4, Feb-Mar-1989) indicates he would have 'The accompanying chart and equations cover all the practical sizes and proportions and are easy to use. On the other hand, if our Editor has sufficient demand, I would be happy to furnish him with a blow-by-blow description of the mathematics and the the method solution including the HP 32S program'. I think fair to say he did the heavy lifting, distilled it to its minimum straightforward steps & made the knowledge available. SIC was one of the key model engineering 'forums' at that time, so it is what it is.

 

[dsage]

The first thing that struck me on the video is that he made the tube he was going to part the rings off of "a nice slip fit" inside the cylinder. Even after doing measurements to try to make it the SAME diameter as the cylinder
The rings are therefore smaller than the cylinder. A problem before he even gets going. This and many other "close enough" errors are what leads to problems.
He also did the light test without a mask to cover the central hole. The mask is a must because staring into a bright light you're never going to see tiny pin pricks or slivers of light leaking around the rings which is what you're looking for.
And yes he never mentioned the ring gap.

BTW Who the heck is Earl (the Guy this Guy is apparently following) and why should we believe Earl or this Guy.

IMHO I would rate this video as just another one to add to the pile of sketchy ring making methods not to be followed.