Whitening

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Whitening

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  • #500039
    Alan Gordon 4
    Participant
      @alangordon4

      Hi Folks, I am progressing well with my build of the Vega Twin. I am at the stage of making the piston rings. In David Parkers construction notes he states that the rings need to be "painted with a thin paste of whiting in methylated spirits". Could any one educated me on what this whitening is and the object of it.

      Many thanks

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      #2591
      Alan Gordon 4
      Participant
        @alangordon4
        #500041
        Michael Cox 1
        Participant
          @michaelcox1

          Whiting is finely ground chalk that is used as a pigment in paints and in papermaking. It is practically pure calcium carbonate. It is a fine white powder.

          For information chalk used on blackboards is not calcium carbonate but calcium sulphate so do norrt be tempted to grind up these.

          #500051
          JohnF
          Participant
            @johnf59703

            Whitening was used extensively to paint ceilings when mixed with water, whats the purpose of painting the piston rings with whitening mixed with meths ? To de-grease maybe?

            John

            #500055
            Brian G
            Participant
              @briang

              Whiting in methylated spirit is a mild abrasive that may be used to clean silver or to prepare glass for gilding. In this case however could the whiting be there simply to protect the piston rings from corrosion until the engine is completed?

              Brian G

              #500060
              Roderick Jenkins
              Participant
                @roderickjenkins93242

                I imagine the whiting is applied to protect the rings from scaling during heat treatment to introduce a sprung gap. Tippex will probably work.

                Rod

                #500068
                JasonB
                Moderator
                  @jasonb

                  I never bother to coat my rings with anything but as Rod says Tippex would stop oxidation though you will then have to clean off the remains of it.

                  #500074
                  Alan Gordon 4
                  Participant
                    @alangordon4

                    Thanks guys, According to Mr. Parker you clamp the rings in a stack, paint on the Whitening, Heat to cherry red allow to cool and remove whitening with a wire brush. This seems a straight forward process but I was just trying to find out why one would do this ? reading on I think Rod has hit the nail on the head. Again thank you all

                    Edited By Alan Gordon 4 on 07/10/2020 14:28:46

                    #500078
                    Gary Wooding
                    Participant
                      @garywooding25363

                      As a child I remember plimsolls (remember them?) being smartened up by whitening them.

                      #500083
                      Fowlers Fury
                      Participant
                        @fowlersfury

                        Quote " According to Mr. Parker you clamp the rings in a stack, paint on the Whitening, Heat to cherry red allow to cool and remove whitening with a wire brush. "
                        Having just spent many hours making Meehanite rings for the loco and breaking 50% of them during fitting, may I offer a note of caution?
                        Clamp the rings but do not heat to cherry red; that's far too hot. It is above the critical temp and will cause metallurgical changes in the iron which are not wanted. After much online searching, I found an excellent article which reviewed (& criticised) some of the expert writings of Tubal Cain, Prof Chaddock etc. Therein it states the correct temp is "480 -520 degC " and not hotter.
                        I borrowed a pyrometer, followed the guidance and no more breakages fitting them over the piston.
                        Don't bother with whiting – at the correct temp there'll be little or no scaling.

                        Unfortunately, the url I have for the article seems to have expired
                        http://www.btinternet.com/~sylvestris/rings/rings.html
                        but if you PM me I'll gladly email you a copy – it's a wealth of information.

                        #500084
                        gerry madden
                        Participant
                          @gerrymadden53711

                          If the whitening is calcium carbonate and its heated to 'cherry red' it will turn into calcium oxide. Isn't this a bit caustic to touch ?

                          #500089
                          KWIL
                          Participant
                            @kwil

                            Putty for glazing is whitening + boiled linseed oil.

                            Edited By KWIL on 07/10/2020 16:28:46

                            #500093
                            not done it yet
                            Participant
                              @notdoneityet
                              Posted by gerry madden on 07/10/2020 15:47:19:

                              If the whitening is calcium carbonate and its heated to 'cherry red' it will turn into calcium oxide. Isn't this a bit caustic to touch ?

                              Not at that temperature. Around 900 degrees Celsius is required to decompose Calcium carbonate. I believe the reaction proceeds quite quickly at 920-930 degrees (the temperature in a the last of a 4 stage preheater – in a dry process cement kiln).

                              Rings only need to be heated until they relax, then cooled. The new ‘set’ of the ring can be repeated to a larger ‘set’ if required. For rings I have ‘set’, the ring was expanded to the required size and then heated until it fell off the expander. They were rather larger rings than the average model steam engine, I expect.

                              I had no idea of the actual temperature but if it is around 500 Celsius, that would be classed as dull-red, I would think. Well, dull-red to most – I can’t easily see it glowing until it gets really hot – being red-green colourblind.🙂

                              #500096
                              Emgee
                              Participant
                                @emgee

                                Jerry Howell provides some details of various methods at this link:

                                **LINK**

                                From what I have seen over the years most use the Trimble method.

                                Emgee

                                #500100
                                Clive Foster
                                Participant
                                  @clivefoster55965

                                  As Fowlers Fury says cherry red is too hot for this sort of thing leading to unwanted metallurgical changes.

                                  Especially as most folks idea of cherry red is more like the "fake" dyed, flavoured and candied glace cherries wot mum used to put in cakes or on top of the icing. Toned down a bit in recent years but back in the day these were just short of Dayglo!

                                  By colour 480 – 520 °C is when the barest hint of red appears in a dark environment. Odds are you will be high when going by colour but, probably not too high.

                                  Clive

                                  #500102
                                  Fowlers Fury
                                  Participant
                                    @fowlersfury

                                    Emgee ~ thanks for posting that link, it is to the article I referred to above – but couldn't now locate its source.

                                    My latest rings were made for the HP valve chamber and thus smaller in size than those for the main (5" scale) cylinders. As, NDIY comments, the rings take a set at the "right" temp. I over-heated the first batch and half snapped as they were gently spread over the valve bobbin. With the pyrometer, the 2nd batch were gently raised to about 500C and allowed to cool amongst the fire bricks. The pre-cut gaps of 2 thou were held apart in the clamp – as below before being covered with the 'fire bricks'. The 4 rings were then sprung over the bobbin without a problem.
                                    b4 heat treatment.jpg

                                    #500123
                                    Rod Renshaw
                                    Participant
                                      @rodrenshaw28584

                                      Emgee,

                                      Thanks for posting that link, I had not seen it before and found it very informative about issues beyond piston rings.

                                      Rod

                                      #500130
                                      SillyOldDuffer
                                      Moderator
                                        @sillyoldduffer

                                        Ah, ye olde receipts recommending hard to find stuff like wrought-iron, ivory, gunpowder and opium. Back when people rode trams to work whiting was common as muck. Not waterproof or sturdy, but wonderfully cheap! Whitewash a cellar by adding some water and boiled horse hooves to a bucketful of whiting powder, and have an urchin stir it. Most of us have moved on to real paint, but it's still used by artists to prepare canvases.

                                        Typex gets my vote!

                                        Dave

                                        #500131
                                        Kiwi Bloke
                                        Participant
                                          @kiwibloke62605
                                          Posted by Emgee on 07/10/2020 17:31:15:

                                          Jerry Howell provides some details of various methods at this link:

                                          **LINK**

                                          From what I have seen over the years most use the Trimble method.

                                          Emgee

                                          Another (prettier) version of Howell's article: **LINK**

                                          'The Trimble method' gets bandied about quite a lot, particularly in the USA. Prof. Chaddock (Loughborough, England) described 'the method' in 1967, long before Trimble's article in Strictly IC – in the '80, IIRC. It's difficult to believe that Trimble was unaware of Chaddock's writings, but his article made no reference to what had gone before. Let's give credit where credit's due – it's 'the Chaddock method'. Of course, Trimble was an American…

                                          #500139
                                          Roderick Jenkins
                                          Participant
                                            @roderickjenkins93242

                                            Interesting use of whiting on the Repair Shop series 5 episode 38. Used to make a mould to bend some glass to repair an SECR railway lamp.

                                            Rod

                                            #500141
                                            Emgee
                                            Participant
                                              @emgee

                                              Hi Kiwi Bloke

                                              I thought the Chaddock method called for the ring to be turned a few thou over bore size but the Trimble method calls for a ring turned to the bore diameter.

                                              Clearly Prof Chaddock was the first to publish a method as far as I know without research, but if the pages of ME's are searched I believe there may be others detailing a method before either Trimble or Chaddock, 1 candidate would be a Mr B Stalham of Kings Lynn whose air cooled vee twin model hydroplane engine appeared on the cover of the ME from memory during the 1950's.

                                              Like many parts there is always a different method of producing it, best to use what suits you.

                                              Emgee

                                              1954    111    2782    341    B.Stalham    A Supercharged Vee Twin. Details of an Experimental 15 cc Engine for a Racing Hydroplane

                                              name changed

                                              Edited By Emgee on 07/10/2020 22:55:49

                                              Edited By Emgee on 07/10/2020 23:00:15

                                              #500313
                                              Kiwi Bloke
                                              Participant
                                                @kiwibloke62605

                                                Emgee – no doubt you're right. I thought the novel principle that Chaddock brought to the problem was heat-setting the rings. My understanding is that this doesn't produce a perfectly-shaped ring, necessitating final skimming, so Trimble's approach may be a bit lacking.

                                                What rankles, however, is the credit given to Johhny-come-lately, Trimble. It's like the electric light bulb. Edison improved it and made it practicable, but he didn't invent it – that was another British invention.

                                                #500330
                                                Emgee
                                                Participant
                                                  @emgee

                                                  Yes no doubt Trimble was aware of the earlier work done by Prof Chaddock, perhaps that's the reason he suggests turning the rings OD to bore diameter, if scaling can be prevented it is less work than finishing the rings to diameter after slitting/breaking and heat treatment, also any minimal out of round shape will be so small that when fitted to the cylinder it will not be detrimental to the engine performance when bedded in.

                                                  Emgee

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