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General => Douglas Motorcycles - General Discussion => Topic started by: george sutton on 08 Dec 2009 at 12:42

Title: Chromeing C/iron cylinders.
Post by: george sutton on 08 Dec 2009 at 12:42
Apparently metal spraying of iron bores is not done. BUT, chromeing the bore IS, followed by honeing.    Has any one had this done? if so, how reliable is it, and how long is it likely to last? your views please. denis .S
Title: Re: Chromeing C/iron cylinders.
Post by: eddie on 08 Dec 2009 at 17:17
Denis,
           The success of any plating job is usually dependant on getting good adhesion to the parent metal. Whilst plating as part of the original specification may be successful, plating of old parts that have been absorbing oil and other contaminants for the last 60 or so years can be problematical. If that plating starts coming away, it can do all sorts of damage as it gets carried around by the oil.
          I have never heard of anyone having postwar Douglas cylinders plated, so I guess you will be on your own regarding working out the correct running clearances.
         As previously advised, the best - and cheapest - option is to use generator barrels. They can usually be bought for a lot less than a new set of pistons!!
                        Regards,
                                 Eddie.
Title: Re: Chromeing C/iron cylinders.
Post by: Dawn on 09 Dec 2009 at 07:59
Following on from Eddie - there may be some generator bits for sale on the for sale section of this forum.  Brian is the person selling the items. 
Title: Re: Chromeing C/iron cylinders.
Post by: george sutton on 09 Dec 2009 at 15:46
Denis,
           The success of any plating job is usually dependant on getting good adhesion to the parent metal. Whilst plating as part of the original specification may be successful, plating of old parts that have been absorbing oil and other contaminants for the last 60 or so years can be problematical. If that plating starts coming away, it can do all sorts of damage as it gets carried around by the oil.
          I have never heard of anyone having postwar Douglas cylinders plated, so I guess you will be on your own regarding working out the correct running clearances.
         As previously advised, the best - and cheapest - option is to use generator barrels. They can usually be bought for a lot less than a new set of pistons!!
                        Regards,
                                 Eddie.
 Hi-ya Eddie,  As an engineer myself, and much experience of cast iron, i fully appreciate what your saying. thats why i asked for views.  with modern techniqes of blast cleaning, maybe i was just being hopefull.   BUT of course, cylinder  pressure will have forced oil wellinto the pores of the metal.   As to the barrels, they are already genny ones.    have hopfully located NEW set of pistons, although std ones, they maybe an improvment on my flogged ones, thanks again, Denis. S



Quote repaired - Dave, 10th Dec, 2009
Title: Re: Chromeing C/iron cylinders.
Post by: george sutton on 11 Dec 2009 at 16:34
Following on from Eddie - there may be some generator bits for sale on the for sale section of this forum.  Brian is the person selling the items.
 

Thank you Dawn for pointing Brians entry out to me, have had some pleasent conversations with him, he claims he is father xmas, and is going to donate the barrels to me ! cant get better than that ,! can you ! merry xmas, Denis.



Fix quote codes. 12Dec09, -Doug, Site Moderator
Title: Re: Chromeing C/iron cylinders.
Post by: LATDOUGNUT on 11 Dec 2009 at 18:30
Hello,

Regarding oil and contaminants in the pores of cast iron cylinders -- this is a similar problem to pores in mazak or pot metal. If you heat up a mazak part quickly the vapours try to escape, block the pores and if petrol vapour or thinner vapour is present in a little pore, the mazak casting will explode and a little piece can be sent flying across the room or into your eye! You will be mad with frustration and usually not fully understand the cause why it happened! So never wash your mazak parts in thinners or petrol before heating them. It does not mean that your cast iron parts will explode if heated, but the pores will behave in a similar fashion. I have found that a powerful ultrasonic cleaner removes contamination from mazak pores very well. At least I have been welding mazak carburettors with good results after 40 minutes in ultrasonic cleaning tank. Previously I used to heat them gradually up in an old kitchen oven (for 3 hours) to 250 degrees Centigrade until all the vapours escaped. After that you could easily weld up even a mazac carburettor which has been soaking in petrol for years(!) using Techno-Weld rods and a small gas/air torch. Use of clay and sand mixture would be called for to protect protruding little items as those could otherwise melt away.

Now everyone who has done welding or flame powder spraying on cast iron will also agree that you need to get the old oil and grease out of the cast iron pores for good results. It can be easily done if you have a town gas or electric heated furnace available -- all liquid oil will burn out (at up to 650 degrees Centigrade) as smoke and the dry deposit left can then be removed by a powerful ultrasonic cleaner. Please remember to use the correct cleaning solution -- it must contain rust inhibitors, otherwise the cast iron part will rust immediately.

Bead blasting an old cast iron part for cleaning (for hard chrome plating) cannot be recommended because the media will clean away only the surface rust and dirt and will close the pores somewhat, leaving the old oil inside. If you do beadblasting and leave the part in the hot sun for an hour or so you will soon notice oil or fat leaking out of the pores! Quite a nuisance if you want to apply primer and paint!

For hard chroming, (it has nothing to do with decorative chroming!) like any other plating of course, preparation is the most important operation and you must do it (the preparation) yourself to guarantee a good result. Firstly you must bore or hone the cylinder to a predetermined size and calculate the thickness of the chrome layer you want to achieve. Try to avoid putting on too much as it will then be prone to peel. A peeling finish will ruin your engine indeed because chrome is very hard (at least HRC 64 )and little pieces of chrome will destroy oilpump gears and everything else in an engine. Hard chrome is very porous and will hold oil well and will withstand hard life. The plater will use a pickle/acid bath before plating the cylinder, so acid should etch away the last remnants of dry deposit left after all cleaning you have done -- I understand that the plater will also place and centralize an electrode into the cylinder to get uniform plating thickness.

Finally it is worth remembering that you cannot use chrome-plated rings in chrome-plated cylinders. Steel and moly rings would last longer than cast iron rings in a chrome plated bore. If the plating is done well you only will need a boron carbide Flex-Hone to improve the surface -- i.e. to remove the sharp protruding surface deposits of chrome and make "plateaued" finish which will bed in the rings and will last a long time.

You should try to find a plater who knows what he is doing and then with your cylinder well prepared and degreased and your fingers crossed the end result should come out good...

Good luck with your project,

LATDOUGNUT
Title: Re: Chromeing C/iron cylinders.
Post by: george sutton on 12 Dec 2009 at 13:21
thank you very much for your very detailed and informative responce. I am hoping that with new pistons and a lightly dressed bores, this work wont be neccessary. denis.s