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Engine Doctor

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Everything posted by Engine Doctor

  1. The last cast iron rod/bar I bought i found on Ebay, Mehanite grade. Also good for making new piston for old diesel engines. Previous to that I have used some old cast iron window sash weights. Failing that have a word with a GC piston rings Gavin might supply some. I forgot to say. Try to find the smallest dia bar as its often difficult to find anything smaller than 30mm and thats a of waistage and time spent getting down to size.
  2. Modern parlance " its just business, nothing personnel". As a modelling community we were lucky the brand didnt ceace production when Niel retired some years ago. I hope you all get the modified parts for you inlines and get thdm in the air. Jon's position is just another example of collateral damage in the closure of the factory who it appears only mades Lasers as a side line. RIP LASER ENGINES
  3. Hi Martin . I have often wondered about C3 bearings for use in our engines. Designed to allow for heat generated especially at start up and the subsequent expansion that can cause bearing failure. I have never actually used them. How do uou find them ? Is the extra clearance noticed in the feel of the engine? What types of engine do you fit them too? I can see a possible advantage on say a Ducted Fan Engine although they are pretty rare these days. With the extra clearance do you choose the sealed type for external/front bearings etc ? How do they compare to standard clearance on our applications ?
  4. Good luck with that one John. I guess foam models were never intended to last so long. Another factor to take into account is the effect of UV on the foam. I kept a small foamy in the spare bedroom that I bought for my grandson. After a couple of years it lterally fell to peices like plastic bags do . Had the room had full sun then I would expect this but it never gets any sun ?
  5. I'ĺl check my bits box but might not be until after Easter weekend.
  6. Welcome back. Yes its changed a lot over the years but you will get all the help you need to get up to speed here on the forum.
  7. Hi John . I bought a second hand edf model some years ago. It had been very badly painted with a sort of red lead coloured paint and looked dreadful . It had to com off. I used a mix of parcel tape and gaffer tape . It did alter the surface a little but still looks fine after a couple of light coats of polyester base coat that gave a satin finish. The trouble with foam is that any paint will creep between the cells of foam and cant be removed. EPP ( Expaded PolyPropelene) foam is ok and you can use various thinners and repaint in a colour that suits ( test a piece first ). As you say heat is out of the question with most foams as it ruins the surface . EPS (Expanded Polystyrene) is best left alone as its very easy to damage and melts at the slightest hint of any aggressive thinners like cellulose. It can be painted with artists acrylic , water based sprayed on neat . Finish off with Ronseal water based varnish again sprayed neat.
  8. Hi Hill climber. The ball bearing does not need to be the same diameter as the CP but dont use a tiny one as its likely to crack the CP. Cast iron is slightly maleable so a good tap often expands it and as its effectively being squashed in the middle it expands equally outwards a few microns but often enough to get a good friction fit. When i make pistons i get them to a sliding fit up to the exhaust port. Then clean and test assemble with plenty of oil and if possible a prop fitted to assist turning the engine . This determines if it still to tight turn over or if it needs a bit more lapping . As soon as the piston passes the exhaust port it should start to compress the air and a bouncy resistance felt . The bounce might not be pronounced if its still tight but be careful if you do any more lapping at this stage as it easy to go tooo far and ruin the piston. Everyone will have their own method . Keep going and you will get there 👍
  9. I was just having a light hearted jibe . Its a quad flying in an orchard so not really interesting or different . If you put vids out then what do you expect and its not as good as Top Gun Maverick ....is it ? I am not good at vids but occasionally put pics of work I have done . If someone doesnt like them fine but I like to know.
  10. 1 min in and eyes were drooping 😌. Not as good as Top Gun Maverick.
  11. You do need a proper fit/seal for the piston as thats how a diesel works. Looking at your picture of the piston it has rounded edges at the crown . This possibly suggests its not parrallel. These shoulders/ edges should be sharp as thats where the seal is important. Re the contra-piston you could try the ball bearing and hammer trick. No its not an early April fool joke. Lay the CP on flat piece of iron. Find a ball bearing that will fit in the top . It must touch the bottom of the recess. Now tap it smartly. Test for fit in cylinder. Repeat until you get a good tight fit but dont over do it . If you hit it too hard the CP can shatter but nothing lost . Its a tip I was given many years ago and has saved many hours of making new CP's. Some CL racing engines that used Cast iron pistons even used this method on the piston crown to finish races Externally its looking good.👍
  12. Hi Jeff I recently fixed a OS die cast backplate with some low temp rods I bought locally . They melt at 300 deg c and seem to make a good strong joint. If interested pm me and I'll send details. They also make a 400deg rod.
  13. Why do that when a proper bearing is available . Many use imperial front and metric rear. bearing . Just measure and order from or speak to Simply Bearings , Only a few engines use "Special manufacturer only sizes" Ive only come across this once on a OS 120 Gemini twin . If Simply Bearings cant get your bearing size then you have an issue .
  14. A good source for bearings is "Simply Bearings" . Excellent service , prices and postage included .
  15. Brilliant work Jeff. What type of welding did you use on the case ? Tig or low temp ?
  16. Your obviously not a member of the "oily hands society".
  17. Hi Charles . For some more realworld tips have a look on YouTube and search for valic000 . Peter Valic is a prolific engine restorer. He recently made a piston for a diesel using a technique he read about . Its done without the usual and sometimes tedious lapping stage. I tried this method on a Frog 150 i was restoring and it was quicker and simple with excellent results.
  18. On scale models , panel lines can be created by simply cutting the brown paper to the size of the panel and glueing over a base covering. The overlap edge simulates panels very realistically. I used this on the frontvof the Hurricane fuz. The stringered part was first covered in tex then thebrown paper overlapped by an inch . Scale panels were then glued on top of the base paper layer. Extrat weight ? In the case of the DB Hurricane the nose needs all the help it can get to balance the tail section. When dried i sealed the surface with a coat of non shrinking dope followed by a light sand . Rivets applied by using thick cyano through a pipette tip guided by a ruler or light pencil line. Then painted using whaterver paint suits . Very realistic ,cheap ,strong and easy to clean up. Glass epoxy is good but expensive ,more difficilt to clean up and no quicker plus temperature has to be kept warm to assure a cure. Many american kits supplied foam blanks with thick brown paper/card for covering . I used to discard the card and use balsa but after using brown paper im rwally ompressed. Ron it may be obvious to us but for begginers it is important to stress that brown paper is only siutable for covering sheeted areas. I have in the past seen attempts from newcomers and not so newcomers to cover open structure 😶 . It doesnt work.
  19. Hi Ron . The last model I covered in brown paper was a DB Hurticane I built for a friend. I found that the brown parcel paper sold at the Post office that had a sort grain along it was very good . I used to paste it with slightly dilute PVA and let it soak like wall paper. It would then take a compound curve very well . Balsa sheet was given a couple of coats of thinned dope to A raise the grain and B seal it slightly. It dried very strong . One thing I found was NOT to use cheap PVA like n* n***ense type home brands. Its good to keep these skills and tips alive . Well done Ron.
  20. Some start up company are likely to get a Government grant/contract ( paid with our tax money) to explore and develop this dream. When it all fades into forgotten memories somebody will be very well off with our money. If anyone in power questions the outcome an inquiry will likely be launched probably headed by lord A.Somthingorother and they will be paid more £1000s again from our tax money to find out what went wrong. This will be dragged out over some years and largely forgotten about...again. If it takes off and works then watch in dissbelief as it sold off to a foriegn bidder and we the tax payer cant even get our potholes fixed. More pie in the sky from the Circus DeUK , but only the rest of the world is laughing!
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