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Club Mills!

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Old 06-25-2013, 06:02 PM
  #226
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Default RE: Club Mills!

Brokenenglish and Jon thanks for the replies. I would like to build the carb if I could get a dwg or sketch of it. I just tried to measure the opening under the piston skirt in the exhaust port. A #78 drill (.016")would not fit. Probably about .010" to .012". Will this affect idle with this carb? Thanks, Larry
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Old 06-25-2013, 06:39 PM
  #227
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Default RE: Club Mills!

G' Day Larry,

That's the subpiston induction.  It would have an affect on throttling but I doubt it would be that much or else Mills wouldn't have succeeded with their throttle design on this engine.

As far as I know engineering drawings of the Mills 1.3 throttle assy. are not in the public domain,  so if you wanted to make your own you would need to borrow a unit and "reverse engineer" it as I did then grind the various form tools and make jigs and fixtures, buy a square stock collet  etc.

Regards,

Jon
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Old 06-28-2013, 12:29 PM
  #228
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Default RE: Club Mills!

Not Mills but a variation on the Mills theme -
I recently came across a new (for me) LD engine, a 0.18cc.
This engine turned up on the local Swedish eBay site. I don't check that site very often but I was lucky this time.
A long time ago I purchased a couple of 0.1cc LD's and then a 0.6cc from a local friend, Ebbe Jensen, who visited Davidovice in Prague in the 80's. I didn't even know that there was a .18 version. It turned out that the seller of the 0.18 engine was also a friend of Ebbe's and had purchased the engine from him too.
Ebbe got to know mr. Davidovice and persuaded him to do two modifications to his original designs: 1) to install proper cast iron contra pistons instead of the aluminium ones that were used in the early versions (apparently popular practice in Czech diesels at the time) & 2) to install steel inserts for the compression screws on the micro diesels - tiny threads in plain alu head easily wear out.
The first photo shows the LD 0.18 - haven't tested it yet but it shows signs of having run and I'm sure it's OK. The other engines are good performers, all three sizes are lined up in photo two. - 0.1cc, 0.18cc & .6cc

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Old 06-28-2013, 03:20 PM
  #229
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Default RE: Club Mills!

Hi Larry, I built a 54" Quaker from a PVHC kit and flew it with an Irvine Mills 1.3. It flew quite well although certainly not over-powered with the Mills running just off flat-chat on a 10" prop. Enjoy! John

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Old 06-28-2013, 03:41 PM
  #230
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Default RE: Club Mills!


Quote:
ORIGINAL: balsaworks

Not Mills but a variation on the Mills theme -
I recently came across a new (for me) LD engine, a 0.18cc.
This engine turned up on the local Swedish eBay site. I don't check that site very often but I was lucky this time.
A long time ago I purchased a couple of 0.1cc LD's and then a 0.6cc from a local friend, Ebbe Jensen, who visited Davidovice in Prague in the 80's. I didn't even know that there was a .18 version. It turned out that the seller of the 0.18 engine was also a friend of Ebbe's and had purchased the engine from him too.
Ebbe got to know mr. Davidovice and persuaded him to do two modifications to his original designs: 1) to install proper cast iron contra pistons instead of the aluminium ones that were used in the early versions (apparently popular practice in Czech diesels at the time) & 2) to install steel inserts for the compression screws on the micro diesels - tiny threads in plain alu head easily wear out.
The first photo shows the LD 0.18 - haven't tested it yet but it shows signs of having run and I'm sure it's OK. The other engines are good performers, all three sizes are lined up in photo two. - 0.1cc, 0.18cc & .6cc


I once owned a Czech "START" diesel, which was without question, the absolute worst engine I have ever owned in my life. Istill think the name was an inside joke as you really couldn't get it to do that.
The MVVS I have are really sweet.
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Old 07-02-2013, 06:00 AM
  #231
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Default RE: Club Mills!

Ed Carlson has Mills 1.3 carburators. I received one in the mail 3 days after ordering, wow. It looks pretty good. I couldn't find anything on the thread. It's .188 dia. and seems to b a couple threads more than a 3-48 tap. I used 1/4-28 on my engine. Should be easy to make an adapter and epoxy the carb in. Larry
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Old 07-02-2013, 06:07 AM
  #232
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Default RE: Club Mills!

Tried to post a photo on the previous post. It didn't go through. Will try again. Larry
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Old 07-02-2013, 06:45 AM
  #233
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Default RE: Club Mills!

From what I remember, I think the Tarno carbs for the TD 049/051 fit Mills engines.
Before people started making RC carbs for Mills, the Tarno Cox carburettor was used and it works well.
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Old 07-02-2013, 06:46 PM
  #234
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Default RE: Club Mills!

For the record Mills .75 and 1.3 venturi thread is 1/4" major dia. by 40 TPI.  Thread form almost certainly would be Whitworth which means a 55 degree thread angle vs. 60 degrees adopted by the USA and the various metric systems.

Proprietary taps and dies are available within the UK and Australia as 1/4" x 40 TPI in the "Model Engineer" series.  This covers a small range of thread diameters in either 32 or 40 TPI.   Could of course single point screw cut such threads on a Lathe capable of machining Imperial thread pitches.  Also could adapt others carbs. like the Tarno Cox TD 049/051 unit by Dremel/filing the carb. and epoxying into the crankcase for those that accept such an approach. 
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Old 07-02-2013, 09:54 PM
  #235
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Default RE: Club Mills!

Jon,
Is my memory playing tricks on me? I'm fairly sure that I read somewhere that the Tarno carb can be screwed directly into a Mills, with no mods or bodging, even though not technically the same thread... Although I appreciate that this may not be your standard of engineering!
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Old 07-03-2013, 01:48 AM
  #236
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Default RE: Club Mills!

Hello brokenenglish,

Cox TD 049/051 venturi thread is 1/4 x 32 UNEF. (Unified Extra Fine) so maybe with a large enough wrench the Tarno carb can be fitted to a Mills........ Most likely can be forced in a couple of threads and whoever tried it might have been happy with that.

I'd prefer to have something properly fitted with correct thread as the "she'll be right" approach as we say here I Aust. usually preceeds some catastrophic failure. I used to fire Engineers and Fitters who were "she'll be right" exponents. Saved a stunning amount of money for companies. They were called "botchers" back in the UK.

Jon
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Old 07-03-2013, 03:40 AM
  #237
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Default RE: Club Mills!

Quote:
ORIGINAL: aeroland

Hello brokenenglish,

Cox TD 049/051 venturi thread is 1/4 x 32 UNEF. (Unified Extra Fine) so maybe with a large enough wrench the Tarno carb can be fitted to a Mills........ Most likely can be forced in a couple of threads and whoever tried it might have been happy with that.

I'd prefer to have something properly fitted with correct thread as the ''she'll be right'' approach as we say here I Aust. usually preceeds some catastrophic failure. I used to fire Engineers and Fitters who were ''she'll be right'' exponents. Saved a stunning amount of money for companies. They were called ''botchers'' back in the UK.

Jon
Jon,

I believe that the Mills 75 has a 1/4" x 40 ME (Model Engineering) thread.

Taps and dies are available in the Hunter Region.

I gently tried a Cox 1/4" x 32 tpi UNEF carby in my Mills and it engages for a few threads only.

An adapter might be easily produced though for this Cox TD Carby available from Cox International.





A male ME 1/4" x 40 tpi on one end and a 1/4" x 32 tpi unef male on the other should work fine.


Ray
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Old 07-03-2013, 04:12 AM
  #238
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Default RE: Club Mills!

A number of years back I modified two Irvine Mills 1.3 cc diesels for USA R/C SAM Texaco event to use carbs other than stock. One was a custom carb with a 2 mm intake. The other a Cox .020 carb unmodified. Both set ups gave longer motor runs on the fuel allotment. Of course at reduced RPM. Both the custom and Cox carbs would better hold a setting than the stock carbs. Both carbs had much finer needle valve threads than stock. Both engines were flown in a Commando along with a stock Mills 1.3 cc diesel. All three engines donated to SAM a couple years back. The two modified Mills would make great engines for scale free flight models. Jack
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Old 07-03-2013, 07:01 AM
  #239
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Default RE: Club Mills!

Jack, there's an easier solution. The Mills 1.3 can be run with a Mills 0.75 carb. (same threads - all original Mills 75 and 1.3 carbs are interchangeable).
The only problem is that both carbs (the 1.3 and the 0.75) are designed to be used with the integral tank, which is no longer possible, unless you want to run the 1.3 on the 0.75 tank...
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Old 07-03-2013, 12:18 PM
  #240
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Default RE: Club Mills!

Jack's engine shown above were both Irvine Mills, not original ones. Irvine made many changes to the Mills 75 design when they produced the Irvine replica-I would not automatically assume that the original 1.3 carb or throttle (1/4-40 thread) would fit an Irvine 1.3 (though this IS the case with the 75 replica)-in any case the Cox unit mentioned above offers an alternative-albeit requiring an adaptor. Brokenenglish's suggestion of switching 75/1.3 carbs certainly works on original and Indian replicas.....and I've used it myself as an overrun failsafe on FF models-even with a 75 carb and tank fitted a 1.3 runs for well over a minute-but that's a lot better than the 4 minutes I can get on the original 1.3 tank.

Somewhere here I have a couple of different 1.3 carbs-one from Dave Banks of VA mini diesel fame, and the other from John Goodall of 'Model Engine World' and 'Barton Model Products' fame. IIRC the latter were actually made by Dunham Engineering sometime in the eighties.

ChrisM
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Old 07-03-2013, 10:14 PM
  #241
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Default RE: Club Mills!

Yes Chris,
Also in the eighties, well-known English collectors Keith Harris and Arthur Fox (my friends and both sadly deceased) made a run of .75 and 1.3 RC carbs, similar to the original Mills one. Keith gave me a couple which I still have. They work well.
The operation stopped when Keith became justifiably cross because someone, that he considered a friend and to whom he'd sold a few carbs, was advertising and reselling them on at twice the price! It wasn't me!!!
Actually, I can't remember who it was, but I'm sure it wasn't John Goodall.
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Old 07-04-2013, 12:07 AM
  #242
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Default RE: Club Mills!

I've always found John Goodall to be a total gentleman, and beyond reproach in his dealings-and I've had quite a few with him-going back to the early 1990s when he started MEW-to which I contributed a number of articles over the years. I've even visited him on a couple of occasions, on my rare trips to the UK. There are a few others in the business though, whose reputation is not quite so snowy white..............

I'll post photos of the carbs mentioned in my earlier reply tomorrow......

ChrisM
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Old 07-04-2013, 02:03 PM
  #243
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Default RE: Club Mills!

OK as promised here are the photos-first up the Dave Banks throttle fitted to a Mk2 series 2. Note that the tank on the throttled one is quite a bit bigger-in fact double the capacity-at 10mls, of the standard Mills 1.3, measured at 5mls [these are both accurate volumetric measurements done with solvent, not just estimates, on the tanks of the two engines in the photo]. Less obvious is that the tank and throttle are an integral unit-the tank assembly rotates (through about a 75 degree arc) as the throttle is moved-as does the NVA-which is machined integral with the throttle barrel. Also fitted is a throttle stop screw adjustment-which is lacking in the earlier Mills throttles and copies thereof.

The second set of pics is the 'universal' Mills throttle-believed to be manufactured by Dunham Engineering-universal in the sense that it fits a 75 and 1.3 (but not the 2.4-the thread diameter is too small!) This one has a body machined from 3/8" square bar, and a steel barrel. No throttle stop as such-and neither has an airbleed of any sort-though one could be fitted to the Dave Banks version without too much difficulty-and the 'Dunham' one could have a fixed airbleed drilled through the barrel at 90 degrees to the normal full throttle opening [but this would have to be done by trial and error-starting with a very very small hole and opening up gradually and incrementally until satisfactory performance is achieved.]

ChrisM
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PS a niggling afterthought prompts me to mention that I think the 'universal' throttles above were not specifically made for Mills, but were applicable to several vintage engines with the same 1/4-40 venturi thread-the Oliver Battleaxe (which was produced by Dunham as a replica) being one such example........
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Old 07-06-2013, 03:05 PM
  #244
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Default RE: Club Mills!

I finally got the carburator fitted and running. Had some problems. Screwed all the way down the needle wouldn't seat. Got it to seat after taking material off the spraybar and nut. It still allowed too much leakage to lean the engine. I unsoldered the needle and lapped it to the seat. Now I can lean the engine for best rpm. I recently got a tach so was able to check rpm before and after putting the carb on. With a wood 10-4 prop it turned 5850-6k rpm. With throttle carb The best I can get is 4850-4950. It idles and accelerates very well. Better then my PAW engines. How does this compare to other 1.3 Mills engines. I think this carb is for Aurora Mills 1.3 engines. Larry
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Old 07-06-2013, 03:49 PM
  #245
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Default RE: Club Mills!

Those revs do seem low-but your engine is a Mk1 series 1-the least powerful version of the 1.3-so it would be expected to be down a bit on revs regardless. Looking at the shot, the carb does seem to be a bit long in the shank-but that may be to provide clearance for the throttle arm (any reason why it could not move rearwards to operate?). From the problems you describe it definitely sounds like an Aurora carb......they're not noted for precision..........

How does the carb bore compare with the standard venturi-if it is significantly smaller then you would expect to see an rpm loss. I would not expect to see a huge speed range either-if you can halve the full rpm revs when the throttle is closed to the idle position then you'll be doing well. Equally-I would not expect to see a lot of throttle linearity either-more like 80% of throttling in the last 30% of movement....!

The OS Max-10 or 10FSR carbs have a good reputation when fitted to diesels around the 1.5cc size, so this would be an area to investigate, though a bit of machine work would be required to adapt one to a 1.3

ChrisM
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Old 07-06-2013, 04:24 PM
  #246
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Default RE: Club Mills!

Thanks Chris, The throat is slightly bigger then the venturi but there seems to be quite a bit of restriction in the throttle area with the spray bar going thru. I think that could be designed better. The front is long because it is epoxied into an adapter I made. It's .188 dia. with an odd thread. I should have shortened it by cutting the thread off. To redo it I would have to heat it quite a bit to break the epoxy loose. Not sure if that would give more power.

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Old 07-06-2013, 04:38 PM
  #247
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Default RE: Club Mills!

Well the Mills in standard form used a surface jet-and that does give particularly efficient fuel atomisation-so with a spraybar that's quite a different setup from the standard. I just see the length of the carb shank in your photo and think 'thats a very long intake tract'-which may or may not have a negative effect. The trouble is-the only way to optimise this is by tedious trial and error-and that means experimenting with the carb and venturi bore (and length!) altering only by a few thou or tenths of a mm at a time. You could expend a lot of time and effort to little useful outcome......
FWIW I generally use the Topflite 10x3-1/2 nylon on my 1.3s..............it seems a very comfortable load for them

ChrisM
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Old 07-06-2013, 06:35 PM
  #248
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Default RE: Club Mills!

Lo and behold-whilst perusing my archives (both extensive and voluminous!) I happened by sheer chance to be trawling through the Dec 1987 issue of RCM&E and found (in the monthly vintage column by Mike Whittard) the pics below. The lower one shows the Mills 'universal' throttle I posted several posts above fitted to the various Dunham Oliver Battleaxe replicas-confirming my suspicions above that it WAS a Dunham Engineering product.

ChrisM
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Old 07-06-2013, 06:58 PM
  #249
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Default RE: Club Mills!

My 1.3s act just like the .75s: put fuel in, flip and off it goes. Can't ask for much more than that.
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Old 07-06-2013, 08:21 PM
  #250
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Default RE: Club Mills!

A demonstration of the above statement. An English Mills .75 fitted with a PAW .55 spinner nut and Aurora NVA and tank assembly. One choked turn, a few flicks and it is off.

This one has first class fits showing very good performace on a Master Airscrew 8 x 3 propeller.

http://www.youtube.com/watch?v=6ej8JTtbq4I

I like this beauty as a perfect use of a Mills

http://www.youtube.com/watch?v=35ASuAt61O8
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