Club Mills!
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RE: Club Mills!
What is the difference between the later 1.3 Mills and mine? Are there dwgs to build one? I enjoy this one so much, I'd like to try another. Hopefully my 82 year old brain can still work through the process.
Thanks, Larry
Thanks, Larry
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RE: Club Mills!
G' Day Larry!
Mk I series I and II Mills 1.3's had aluminium crankcases and fabricated parts for the venturi and tank assy.
The Mk II's used diecast magnesium crankcases dichromated black to resist corrosion. The Mk II series II had a lower venturi centreline giving extended port timing and hence more power. The Mk II venturi was a dropped forged aluminium part.
Regards - Jon
Mk I series I and II Mills 1.3's had aluminium crankcases and fabricated parts for the venturi and tank assy.
The Mk II's used diecast magnesium crankcases dichromated black to resist corrosion. The Mk II series II had a lower venturi centreline giving extended port timing and hence more power. The Mk II venturi was a dropped forged aluminium part.
Regards - Jon
#253
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RE: Club Mills!
Hi Larry,
The early Mills 1.3 (1946) had the crankcase that yours has. As you can see, the case is a light alloy casting with a machined finish. The shape is mostly simple straight lines, resulting in a fairly heavy engine for that period. Nowadays, weight isn't a problem of course but, at the time, great efforts were made to keep engines as light as possible, particularly for free flight applications.
There were two "sub-types" of this first model Mills but, for what you're considering, the differences are negligible (mainly the contour of the head fins).
Anyway, at the time, the early Mk I Mills was acknowledged as being a great runner, but was criticised as being a bit heavier than necessary.
Mills therefore produced a lighter version, with a black magnesium case (from 1948), and this has become the most commonly used Mills 1.3.
I could post photos, but both versions are already shown a little higher up in the thread.
On both models, Mills made minor changes, mainly lowering the inlet port slightly on the rear of the case (you can see that the carburettor is visibly lower on later engines) but again, for your purposes, you can consider all Mills 1.3 engines to be virtually the same mechanically.
Regards,
Brian
The early Mills 1.3 (1946) had the crankcase that yours has. As you can see, the case is a light alloy casting with a machined finish. The shape is mostly simple straight lines, resulting in a fairly heavy engine for that period. Nowadays, weight isn't a problem of course but, at the time, great efforts were made to keep engines as light as possible, particularly for free flight applications.
There were two "sub-types" of this first model Mills but, for what you're considering, the differences are negligible (mainly the contour of the head fins).
Anyway, at the time, the early Mk I Mills was acknowledged as being a great runner, but was criticised as being a bit heavier than necessary.
Mills therefore produced a lighter version, with a black magnesium case (from 1948), and this has become the most commonly used Mills 1.3.
I could post photos, but both versions are already shown a little higher up in the thread.
On both models, Mills made minor changes, mainly lowering the inlet port slightly on the rear of the case (you can see that the carburettor is visibly lower on later engines) but again, for your purposes, you can consider all Mills 1.3 engines to be virtually the same mechanically.
Regards,
Brian
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RE: Club Mills!
Thanks Brian, I made the crankcase from bar stock I had laying around. Probably 6061 T6. The crankshaft is from a grade 8 bolt using the head for the crank end. I don't remember what I used for the cyl. The piston is cast iron. The article and dwg. by Ron Chernoff are in the first issue of Model Maker Machinist Magazine. The dwg is superb and easy to work from.
Larry
Larry
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RE: Club Mills!
G' Day Larry,
You are to be congratulated on your Mills 1.3 replica! I knew it wasn't original and initially guessed it might have been an English made Attachport replica. Using a high tensile steel bolt as material for a crankshaft is an elegant solution as you get the benefit of grain flow following the contour which doesn't happen with a bar stock machined part.
One thing I found out after reboring Mills .75 engines that the original Mills pistons were hardened tool steel, not cast iron. So for my next Mills .75 rebore I made one from silver steel (like drill rod blank in the USA) and oil quench hardened it. Final sizing I do by lapping not honing and lapping of the hardened steel piston took a lot longer. The end result was greatly superior both for starting and running. Subsequent Mills .75 rebores I have done with hardened steel pistons also with superior results. Mills original contra pistons wre just mild steel and often wear to become loose in service. Making them from cast iron lapped to fit gives a better than original part.
Regards - Jon
You are to be congratulated on your Mills 1.3 replica! I knew it wasn't original and initially guessed it might have been an English made Attachport replica. Using a high tensile steel bolt as material for a crankshaft is an elegant solution as you get the benefit of grain flow following the contour which doesn't happen with a bar stock machined part.
One thing I found out after reboring Mills .75 engines that the original Mills pistons were hardened tool steel, not cast iron. So for my next Mills .75 rebore I made one from silver steel (like drill rod blank in the USA) and oil quench hardened it. Final sizing I do by lapping not honing and lapping of the hardened steel piston took a lot longer. The end result was greatly superior both for starting and running. Subsequent Mills .75 rebores I have done with hardened steel pistons also with superior results. Mills original contra pistons wre just mild steel and often wear to become loose in service. Making them from cast iron lapped to fit gives a better than original part.
Regards - Jon
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RE: Club Mills!
Thanks Jon, I lapped the contra piston a few tenths larger at the skirt end also lapped the cyl. a few tenths smaller at the top. It had drag at first but turns free now. I can hold it against compression for a long time without bleed down. Made the wrist pin out of a piece hardened drill shank. The dwg. showed a full floating pin. I didn't like the idea it rubbing the cyl. wall, so I made it a press fit in the piston.
Larry
Larry
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RE: Club Mills!
G' Day Larry!
Piston fit sounds good! It would be normal to get some drag on newly made piston and bores. Some of that is due to the engine having to change the direction of lay of the surface finish from circumferential to axial, which it does in the process of running in. I tend to start on the tight side of course as I have yet to find a metal putting on tool.... Part of the test running is to adjust the piston to bore fit until it is free yet holds compression forever, hot.
With fully floating gudgeon (wrist) pins I make the final length of the pins about 0.010" less than the bore dia. This to give maximum wear surface in the piston's pin bores. I radius each pin end to just less than that of the bore. Sharp cornered pins can score bores as well as ones badly made with the part off pip left on. Providing the pin hole in the piston is good and square to its OD and the conrod bores are also good and square no bore marking will occurr with radiussed end pins. Press fit pins can distort the piston if it is a bit lightweight and can become fully floating after some running. Radiussing the pin ends I find works very well.
Best regards,
Jon
Piston fit sounds good! It would be normal to get some drag on newly made piston and bores. Some of that is due to the engine having to change the direction of lay of the surface finish from circumferential to axial, which it does in the process of running in. I tend to start on the tight side of course as I have yet to find a metal putting on tool.... Part of the test running is to adjust the piston to bore fit until it is free yet holds compression forever, hot.
With fully floating gudgeon (wrist) pins I make the final length of the pins about 0.010" less than the bore dia. This to give maximum wear surface in the piston's pin bores. I radius each pin end to just less than that of the bore. Sharp cornered pins can score bores as well as ones badly made with the part off pip left on. Providing the pin hole in the piston is good and square to its OD and the conrod bores are also good and square no bore marking will occurr with radiussed end pins. Press fit pins can distort the piston if it is a bit lightweight and can become fully floating after some running. Radiussing the pin ends I find works very well.
Best regards,
Jon
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RE: Club Mills!
An article from Model Engine World in 1997 concerning the Doonside Mills engines, and others.
It may need to be printed to an A4 hardcopy to be legible.
It may need to be printed to an A4 hardcopy to be legible.
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Will do Brian.
It is jumping to the head of my queue for testing. I will run it this week end. I would like to ultra sonic or solvent clean it however I am concerned the black enamel finish may not like it. Internals are liberally coated with grease. I will spray flush the top and bottom ends with solvent, air tool oil it, and put it on the bench. Mechanically, it feels good. No obvious faults. No play in the rod ends. Rod itself is workmanlike in finish. Smooth bearing and good piston seal. The turned alloy parts are very nicely done.
Warren B (in Victoria, Australia) has one. It is shown earlier in this thread; post # 3 on page 1 and again in post # 100 on page 4. His differs from this one in the the prop driver. The cooling fin profile also has some minor variances. Warren stated that power is not that far behind a PAW of the same capacity on large props.
Who will be the first to guess what that oblong white object is inside the spinner nut?
It is jumping to the head of my queue for testing. I will run it this week end. I would like to ultra sonic or solvent clean it however I am concerned the black enamel finish may not like it. Internals are liberally coated with grease. I will spray flush the top and bottom ends with solvent, air tool oil it, and put it on the bench. Mechanically, it feels good. No obvious faults. No play in the rod ends. Rod itself is workmanlike in finish. Smooth bearing and good piston seal. The turned alloy parts are very nicely done.
Warren B (in Victoria, Australia) has one. It is shown earlier in this thread; post # 3 on page 1 and again in post # 100 on page 4. His differs from this one in the the prop driver. The cooling fin profile also has some minor variances. Warren stated that power is not that far behind a PAW of the same capacity on large props.
Who will be the first to guess what that oblong white object is inside the spinner nut?
Last edited by fiery; 09-12-2013 at 12:10 AM.
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Fairly new member here, not only to "Club Mills," but also RCU in general.
That being said, my diesel collection has grown rather quickly (probably too fast, by the looks of my empty billfold and my wife's face!), and I figured I'd chime in.
Regarding Mills-type engines, I have acquired two MP Jet 040PB Classics, an Aurora 1.3cc replica, and an original Mills 1.3 Mk1 Series 2 engine. I'm hoping to pick up a CS 0.5cc replica soon as well, but like I said, the pocketbook needs a bit of a break, so it'll likely be a month or two before that happens. All appear to be in good condition, though one of the MP Jets is gummed up, and I'll be taking the Aurora apart to clean out any swarf I find, as seems to be the recommended practice. I plan to get pictures taken shortly here, and get them all running soon enough.
That being said, my diesel collection has grown rather quickly (probably too fast, by the looks of my empty billfold and my wife's face!), and I figured I'd chime in.
Regarding Mills-type engines, I have acquired two MP Jet 040PB Classics, an Aurora 1.3cc replica, and an original Mills 1.3 Mk1 Series 2 engine. I'm hoping to pick up a CS 0.5cc replica soon as well, but like I said, the pocketbook needs a bit of a break, so it'll likely be a month or two before that happens. All appear to be in good condition, though one of the MP Jets is gummed up, and I'll be taking the Aurora apart to clean out any swarf I find, as seems to be the recommended practice. I plan to get pictures taken shortly here, and get them all running soon enough.
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Very cute fiery-I shudder to think how far down that mills must be geared to propel a 'locomotive at that sedate speed. Looked like a 'light case' Irvine with the big 'R/C type' tank (or possibly the 1.3 tank assembly fitted....)
ChrisM
'ffkiwi'
ChrisM
'ffkiwi'
#272
FIERY Neat super smooth, great response idle to WOT just like a big one a winner it is, my sure start Cox 049 fitted with same carb
works well but not quite as smooth on transition martin
works well but not quite as smooth on transition martin
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Where does one source the carb from?.....ie are they available as a separate item or spare or was it cannibalized from a CS engine?
ChrisM
'ffkiwi'
...I'm thinking that carb would really add another dimension to Tomboy flying.....
ChrisM
'ffkiwi'
...I'm thinking that carb would really add another dimension to Tomboy flying.....
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I don't believe the carbs are available for sale directly over the internet in a 'point and click' format.
The two sources I know of for 'plug and play' R/C carbs for Mills type engines are:
1. The Aurora R/C versions of the K Mills. The Aurora R/C carb is a good copy of the PAW carb and is BA threaded. It will fit 'English' Mills and Irvine Mills .75's. Carlson Engine Imports may be able to supply R/C carbs. I have not checked. Ed Carlson supplies (or used to supply) R/C carb equipped Aurora K-Mills engines.
2. CS Engines. CS sold, or used to sell, the CS 'Mills' type engines with an R/C carb option. The carbs come (or came) in two sizes. One for the .5 cc and .75 cc engines, and a larger bore one for the 1.3 cc. The spigot is metric thread. The small size CS R/C carb fits right up to the MP JET .040 PB classic as the thread is the same. I acquired mine some time ago by asking the factory by email. As of Dec. 2013, they are sold by the "redfin" retro diesel engine distributor:
http://www.redfinengines.com/product...y/accessories/
I expect the R/C carb for a PAW .049 would do just as well. It is readily available from a number of distributors. An intake adaptor would be required though.
The two sources I know of for 'plug and play' R/C carbs for Mills type engines are:
1. The Aurora R/C versions of the K Mills. The Aurora R/C carb is a good copy of the PAW carb and is BA threaded. It will fit 'English' Mills and Irvine Mills .75's. Carlson Engine Imports may be able to supply R/C carbs. I have not checked. Ed Carlson supplies (or used to supply) R/C carb equipped Aurora K-Mills engines.
2. CS Engines. CS sold, or used to sell, the CS 'Mills' type engines with an R/C carb option. The carbs come (or came) in two sizes. One for the .5 cc and .75 cc engines, and a larger bore one for the 1.3 cc. The spigot is metric thread. The small size CS R/C carb fits right up to the MP JET .040 PB classic as the thread is the same. I acquired mine some time ago by asking the factory by email. As of Dec. 2013, they are sold by the "redfin" retro diesel engine distributor:
http://www.redfinengines.com/product...y/accessories/
I expect the R/C carb for a PAW .049 would do just as well. It is readily available from a number of distributors. An intake adaptor would be required though.
Last edited by fiery; 12-01-2013 at 10:34 PM.