Formtex1947 Posted May 16, 2017 Share Posted May 16, 2017 Posted by Formtex1947 on 16/05/2017 09:38:01: Hello fellow diesel users, I have the age old comp screw crawl on my A-M 1 CC and was wondering if anyone knows what thread the cop screw is on the "green Head" to allow me to obtain a tap to make a suitable locking device? Would appreciate any help or advice. Regards Richard Quote Link to comment Share on other sites More sharing options...
Alan Gorham_ Posted May 16, 2017 Share Posted May 16, 2017 Richard The AMs definitely used BA series threads. My guess is 4BA for the comp screw. I have two examples at home so will check for you tonight. Quote Link to comment Share on other sites More sharing options...
onetenor Posted May 16, 2017 Share Posted May 16, 2017 If you can measure the diameter of the screw I can tell you which B.A. size it is if you tell me Quote Link to comment Share on other sites More sharing options...
onetenor Posted May 16, 2017 Share Posted May 16, 2017 One solution is to tap it out bigger but tap it on the tight side Up to say 2B.A. I did that on a Merlin and to adjust with a cowl in place used a Cap head bolt. Another is to braze a lever onto a suitable nut, and use that as a locknut. Another old trick was to put a spring round the comp screw bearing on the lever and the head. . This tensions the screw against the thread. and stops the creep. Quote Link to comment Share on other sites More sharing options...
onetenor Posted May 16, 2017 Share Posted May 16, 2017 Steve why is the A.M.10 a non runner If it is just gummed up warm it up and free it off enough to move then flush it through with fresh fuel until it is totally free .Clean out the needle assy put back together Slap on a prop and run it. Quote Link to comment Share on other sites More sharing options...
Alan Gorham_ Posted May 16, 2017 Share Posted May 16, 2017 Posted by Formtex1947 on 16/05/2017 15:21:56: Posted by Formtex1947 on 16/05/2017 09:38:01: Hello fellow diesel users, I have the age old comp screw crawl on my A-M 1 CC and was wondering if anyone knows what thread the cop screw is on the "green Head" to allow me to obtain a tap to make a suitable locking device? Would appreciate any help or advice. Regards Richard Richard Just checked one of my AM-10s and can confirm that the comp. screw thread is 3BA. Quote Link to comment Share on other sites More sharing options...
onetenor Posted May 16, 2017 Share Posted May 16, 2017 Good work I suspected it might be an odd size Quote Link to comment Share on other sites More sharing options...
Bob Cotsford Posted May 17, 2017 Share Posted May 17, 2017 Back in the day we used to drape a section of thin rubber band or nylon thread into the hole in the head before putting the comp. screw in to provide a bit of friction. This worked quite well, when it stopped working it was a simple matter to replace the rubber band. Quote Link to comment Share on other sites More sharing options...
Mike Etheridge 1 Posted May 18, 2017 Share Posted May 18, 2017 Currently I have an ED Racer MK 2, an AM10, a PAW 1.49 a PAW 29 RC and a Marine ED Sea Otter. Only the Racer has been used fairly recently. I started off when I was 12 with a DC Merlin, whereas both my school mates had Mills 0.75's which were much better quality. I always had problems with the Merlin which needed far more running-in time than the Mills, but behaved itself when I used Mercury 8 fuel. As I have reported before the Merlin disappeared with my Southern Dragon plane at Epsom Downs in September 1962. Someone must still have my Merlin? Quote Link to comment Share on other sites More sharing options...
onetenor Posted May 18, 2017 Share Posted May 18, 2017 Does anyone know of a metal rod or studding that I can cast alloy round then remove it later This is to rebuild a broken exhaust stub. My first engine was an AMCO .87 cc which I still have but the carb assy is missing Can anyone help.I'm not looking for a freebie .I will pay a reasonable price. I am considering converting a Mills .76 cc carb has anyone done this? Quote Link to comment Share on other sites More sharing options...
Denis Watkins Posted May 18, 2017 Share Posted May 18, 2017 Your repair idea is genius John, but is fraught with difficulty. Just from the point of view of dissimilar materials, pouring hot alloy metal onto say, cold steel pin would verge on an eruption. It would be dangerous too. The best metal poured plugs are sand, clay or timber, but these are impractical A guy on the BMFA site, fits inserts for £16 if there is enough meat on the job Quote Link to comment Share on other sites More sharing options...
onetenor Posted May 18, 2017 Share Posted May 18, 2017 Oops .75cc not.76cc Quote Link to comment Share on other sites More sharing options...
thomas oliver 1 Posted June 20, 2017 Share Posted June 20, 2017 I have made quite a few comp screws for AM diesels in the past and the thread is in fact 3/16th in Model Engineering. T,O Quote Link to comment Share on other sites More sharing options...
Martin Harris - Moderator Posted June 20, 2017 Share Posted June 20, 2017 Posted by Denis Watkins on 18/05/2017 09:54:46: Your repair idea is genius John, but is fraught with difficulty. Just from the point of view of dissimilar materials, pouring hot alloy metal onto say, cold steel pin would verge on an eruption. It would be dangerous too. The best metal poured plugs are sand, clay or timber, but these are impractical A guy on the BMFA site, fits inserts for £16 if there is enough meat on the job I've done a similar exercise with Lumiweld using a stainless steel bar in the broken exhaust port of an OS120 FS - I believe it held OK although the clubmate I did it for left the club a little while later. Nice and clean to start with, then scratch/stir the Lumiweld pool against the head as it starts to melt, with a thin stainless rod. Quote Link to comment Share on other sites More sharing options...
thomas oliver 1 Posted June 22, 2017 Share Posted June 22, 2017 Further to my post re AM10 comp. screws, note that the larger AM engines have a 7/32in x40 tpi Model Engineer thread. T.O. Quote Link to comment Share on other sites More sharing options...
onetenor Posted June 22, 2017 Share Posted June 22, 2017 I am not pouring hot metal I am using soldering techniques Denis. Heating base and offering alloy solder to the hot stub until it melts. as is described by Martin Harris above. I have done alloy welds ,also using Lumiweld or Techweld , before but not needing in past to cast a thread.Hence my query re thread size.Talking of which anyone know thread size for Magnum/O.S. 40 NVA ? Quote Link to comment Share on other sites More sharing options...
onetenor Posted June 22, 2017 Share Posted June 22, 2017 I am not pouring hot metal I am using soldering techniques Denis. Heating base and offering alloy solder to the hot stub until it melts. as is described by Martin Harris above. I have done alloy welds ,also using Lumiweld or Techweld , before but not needing in past to cast a thread.Hence my query re thread size.Talking of which anyone know thread size for Magnum/O.S. 40 NVA ? Quote Link to comment Share on other sites More sharing options...
Formtex1947 Posted June 25, 2017 Share Posted June 25, 2017 Thanks folks for the Various ideas to improve my creeping AM.10 Comp screw will check them out and advise. Regards & thanks Richard Quote Link to comment Share on other sites More sharing options...
onetenor Posted June 29, 2017 Share Posted June 29, 2017 I can't find a screw matching the sizes you gave me .Check again and give me imperial size as well please . John Quote Link to comment Share on other sites More sharing options...
Denis Watkins Posted June 29, 2017 Share Posted June 29, 2017 Check out M4, or 3BA, gently Quote Link to comment Share on other sites More sharing options...
Denis Watkins Posted June 29, 2017 Share Posted June 29, 2017 Woops, mine was for the NVA Quote Link to comment Share on other sites More sharing options...
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