Irvine Mills .75 replica

I have a "small" collection of the Mills ( and Replica) engines:

My .75 and 2.5 Aurora Mills:



Aurora K-Mills  (early edition is black / later just sand cast - no paint)75:



CS (Bodo) Mills 75 and 1.3:




Doonside Mills P-75 Replica-Russia:



Two Mills from Tower Hobbies ---- imported Irvines Mills 73 ( back in the mid 1980's):





Last is my "Limited Edition" .75 and 1.3 Irvine Mills which was sold .75 and 1.3 together in one box.
Four boxes --- Eight engines.


And more that I don't have photos of.

The best ones I like are the Boddington Mills. Best running of them all besides the one Doonside Mills which I used for many years in my 36" Freeflight Tomboy at SAM Champs contests.

Nice Collection mike !!

Hi sosam,

Would any of your mills 75's have a none slotted or small holed or hex holed crank case cover. The one I have has the deep circular large diameter depression, with opposite sided internal triangular webs, to engage with a suitable flat bar tool to unscrew the end plate.
The "carb" is tubular not square section, and the tank mounting plate has two alloy tangs .

The only numbers I can find are on the engine mountings upper surface, left being 42 and right being 765 or 785.

The compression screw is T shaped.

Any help identifying this engine gratefully received....pictures to follow....

Engine number is 765...

Engine has spi like a Cox........

The tank plate upper surface opposite the filling hole seems to have a T and a couple of other stamped markings.....

What you are describing is an original British made Mills 75-the numerals represent firstly a production batch-the '42' and then the engine's number within that batch-'765' or '785'. the round induction tube is normal for a British (and indeed Indian repro-the latter use the original British tooling-ie the manufacturing jigs and fixtures) A T-shaped compression screw however is not original-it should be L-shaped. Sub piston induction is normal-but the amount varies from batch to batch-some engines have virtually none, others quite a lot. I have no comment to make on the tank top markings..except to note that this is NOT a normal feature of British made Mills 75s

ChrisM
'ffkiwi'

ffkiwi might be correct that you have an "original" British made Mills.
I have one as well but never have run it.
The contra screw is an "L" shape and in the "bee" head is a little pin so that the contra "L" shaped screw is limited to 1 turn compression.
The SPI is about almost nothing that I can see.
The British Mills .75 that I have, was given to me as a gift from Allan Lacock from Australia for setting up and flying my old timers at the SAM Champs in Sept 2008.

Built a FreeFlight Tomboy for it for Allan to use his Mills in.
When he went back home, Allan said I can keep the Mills.

So, when Allan wants to fly FreeFlight he has a Tomboy to fly, but I let him use one of the "newer" Mills engines.

I'll have to dig around to find the engine (among the hundreds of Enya, O.S., PAW, and countless other mfg. engines) and take photos of it?

Thanks guys, this engine is in the "clean me" q, a light external clean and then the rear cover off ( red fibre washer ) to check for rod/cylinder issues, the run up.

Have seen a vidio of a mills with a T shaped compression screw version, the dad and his young lad one .

The beehive head does have the compression stop pin hole but no pin...
.
The tank top, the spray bar hex head has what looks like *pliers rash* and the tube looks like having a course thread, so may have been changed at some point. The needle adjust wheel looks as if it may be brass, and may be soldered onto the needle.....

Any comments on rear cover means of undoing/tightening, any clues there ?

Over......

Coxfledgling wrote:Thanks guys, this engine is in the "clean me" q, a light external clean and then the rear cover off ( red fibre washer ) to check for rod/cylinder issues, the run up.

Have seen a vidio of a mills with a T shaped compression screw version, the dad and his young lad one .

The beehive head does have the compression stop pin hole but no pin...
.
The tank top, the spray bar hex head has  what looks like *pliers rash* and the tube looks like having a course thread, so may have been changed at some point. The needle adjust wheel looks as if it may be brass, and may be soldered onto the needle.....

Any comments on rear cover means of undoing/tightening, any clues there ?

Over......

Can you take a photo of the backplate?

Now, on a PAW backplate the slot is curved and to remove that I use a slug/washer of the correct size that fits the curvature and clamp down on the washer in a vice (1/2 way), heat the engine up (heat is our friend) and insert the backplate on the engine onto the slug sticking up 1/2 way out of the vice and turn the back plate off.

Now if yours is a straight slot. I use a piece of straight steel and do the same thing as the PAW engine backplate.
Make sure that you are pressing down firmly on the front of the engine so that the backplate dosen't slip off the straight piee of steel!

Below are photos of how I remove the backplate on the Aurora Mills.

1.) Backplate on Aurora 75 Mills ( straight slot)


2.) Straight bar width is almost same width as back plate slot.


3.) Straight piece of steel clamped into vice (1/2 way in vice)


4.) Heat up engine with heat gun (covering gun) till it is extremely warm (HOT - make sure you are wearing gloves for this!)
Then line up the backplate slots onto the straight piece of steel in the vice.


5.) Now with the backplate slots on the bar ( and pressing down on the front of the engine - spinner end) turn the engine counter clockwise and remove the backplate.


Now if done correctly, you will have removed the backplate.

To reinstall the backplate you just have to do the reverse (but you don't need to heat up the engine and you don't need to use the vice either, just use the straight piece of steel as your wrench and screw the backplate back on.)

Yep, know about that method etc...

The back plate on mine has the *hole* but no means of undoing the plate via slots on the periphery etc..

Inside the hole, from the holes "sides" , to the hole floor, there are two things *webs*, inclines if you will, to allow a suitable steel strip to be inserted, sane width as hole diameter, so the strip butts up against the Webb's, to allow the back plate to be turned.

The Webb's do not cross the hole or connect to each other, they are individual.

I will clean out the muck and post a picture.

Seen on sceptre flight, mills 75 history, components picture on left, backplate hole, possibly hints at these Webb's/inclines.....no slots seen....

Ps, silly me, hex view is prop nut, doh !!!!!

You remove the backplate on an original Mills 75 by using a piece of round material-which is a snug (but not tight) fit inside the backplate hollow. This has a slot cut diametrically across the face just wide enough to clear the two cast in triangular webs in the backplate hollow. A piece of wooden dowel with a suitable sawcut will suffice-though the tool I use is made from alloy rod, with a tee bar handle at the other end.

some engines are like this and require a custom tool...I have others (not Millses!) in my stable that have a hexagonal shape for the inside of the backplate and you use a piece of hexagon stock to unscrew them; the Nelson 15 has a glowplug size male hex machined in the centre of the backplate and a normal glowplug spanner can be used to unscrew the backplate. Most screw in backplates though simply have the shallow slot milled ion the rim for unscrewing-and the straight bar method sosam shows above works fine...

ChrisM
'ffkiwi'

Thanks guys, but does this back plate *narrow down * the engines identification at all please ?

I suspect the fuel tank plate may have been changed at some point along with the compression screw .

The engine numbers look original, but research has not shown location other than on the side of the engine bearers, nine are left and right between bolt holes and only seen from above. I suspect the back plate is original also.

Anyways we shall see what is seen after a clean. It's coloured black and looks very much like other black ones seen.

Coxfledgling wrote:Thanks guys, but does this back plate *narrow down *  the engines identification at all please ?

I suspect the fuel tank plate may have been changed at some point along with the compression screw .

The engine numbers look original, but research has not shown location other than on the side of the engine bearers, nine are left and right between bolt holes and only seen from above. I suspect the back plate is original also.

Anyways we shall see what is seen after a clean. It's coloured black and looks very much like other black ones seen.

You are either confused-or else your research is inadequate. I have already told you that you have an original British Mills-and the basis behind the numbers-they are ALL like that-on all original Mills bros Mills engines-the 75, 1.3 and 2.4....a 2 digit batch number on the top of one lug and a 3 digit 'number within batch ' number on the opposite lug. You are perhaps confused by other Mills: the Irvine Mills 75s have a serial number stamped on the SIDE of the lug; the Australian made Doonside have a serial number stamped on the underside on the front of the crankcase below where the main bearing housing emerges ; the Russian made Doonside on the underside of a mounting lug 9often with the letter 'Z' on the other underside, and the Indian made ones have no serial number. Likewise the backplate with the internal webs in the hollow is ONLY found on the British made originals-and not on any others. take it as fact from someone who has been playing with these for 55+ years-and has examples of all the types I've mentioned... Your comp screw as previously stated is NOT original.

ChrisM