Mills 1.3

[Ghosty]

Hi All,

I looked into making a Mills 1.3 engine as they are getting very hard to get.

Found a web site with plans Oz : Mills 1.3 plan - free download

Printed the plans out and studied for a few hours. Have found many mistakes in downloaded plans in the past.

Found a mistake, width of the starter block for the crankcase was marked at 1-9/16" wide. on plans the width of the crankcase is total of 1.654" a difference of 0.0915".

After double checking dimensions, I checked on what I had at hand. I had enough to get started with.

First got the material cut, then squared up and sized the block for crankcase.

Then marked out and drilled 4 holes for the mounting lugs, then drilled and tapped the 4 holes for the cylinder mounting.

Will move on to crankcase machining tomorrow.

Cheers

Andrew

 

[Ghosty]

Hi All,

Started the machining of the crankcase, setup, trued and centered, machined crankshaft pocket and bore, and threaded for backplate, thread is listed at 26TPI, as I can't cut imperial threads on my lathe, I used a 1mm pitch and the dia listed on the plans.

Then rotated the case, trued and centered then machined the cylinder bore.

Then moved to the mill, machined conrod relief, exhaust ports, and transfer port.

Will now move on to machining the outside or the case.

Cheers

Andrew

 

[Ghosty]

Hi All,

Got on with the outside of the crankcase/body.

Started with the base/engine mount lugs, then the top sides, then cut the sides to the angle.

Then machined up two jigs to hold the case to machine on the lathe.

Machined the nose of the case and then on to the mill again to machine the base of the case.

Then glass bead blasting to get the finish on the case, then back on the lathe to do the final machining(sorry no pics of machining) of case.

Great care is needed when you do this step so you don'y drive the tool into the case.

Cheers

Andrew

 

[Ghosty]

Last couple

 

[Ghosty]

Hi All,

P.S. Remounted crankcase to show final cutting of case. tool post compound set at 7deg for cutting.

Access for grub screw is through the crankshaft pocket.



Cheers

Andrew

 

[Ghosty]

Hi All,

Worked on the cylinder today.

Machined the first end out of square bar, thread should have been 0.540" x 26TPI, I used M14x1(0.551") as I cant cut imperial threads on my lathe.

Then, with a bit of 19mm hex bar, I drilled and tapped M14x1 to use as a jig to hold the cylinder , so I can machine the other end.

I machined down the other end to fit the case body, then drilled and reamed to 0.406".

Then I started on the cooling cap. Drilled and tapped M14x1, and checked fit of cylinder.

Machined the cooling fins, parted off, tapped for compression screw, then machined compression screw and assembled.

Cheers

Andrew

 

[Ghosty]

Hi All,

Started on the crankshaft today, machined the crankshaft bearings from bronze and installed in cases, then reamed to size.

Machined and tapped the nut from 7/16" hex bar.

Centre drilled the crank blank, and then machined the end down for the threaded end as per plans.

Then machined crank down to suite the bearings, then machined taper on shaft.

Machined the prop drive hub, cut slots to drive hub instead of using drive pins as plans.

Cut groves with tool on side, 15thou deep.

Cheers

Andrew

 

[Ghosty]

And a couple more

 

[Fluffy]

Well done Andrew. I like what you are doing, keep up the good work, it will be good to see them running.
Regards,
Don.

 

[Ghosty]

Hi All,

Started on the fuel tank/venturi today.

Machined the tank body from Perspex and alloy.

Machined needle valve from 1214, machined venturi/needle/jet in two pieces. Machined nut(5/16) from 10mm round bar.

Assembled needle/jet/ fuel tank top/venturi with loctite, when set drilled through and then cleaned out jet and needle threads.

Cut fuel tube piece and assembled fuel tank.

Cheers

Andrew

 

[Ghosty]

Hi All,

Started with conrod machining today.

Used a piece of 7075 10mm alloy plate, cut a 10mm slice off and squared up.

Marked out and drilled and reamed big and little ends to size.

Then machined to thickness, then machined centre section to thickness.

With the use of a 1mm(big end) and a 1.5mm(little end) drill bits I machined the outer sides to size.

Then machined the outer big, and little ends.

Still have the final finishing to do.

Cheers

Andrew

 

[Ghosty]

Hi All,

Finished of machining of the crankshaft today.

First machined up a jig to hold the crankshaft with correct offset for big end.

Fitted crank in jig and then machined the big end to suite the conrod.

Then moved assembly to the mill to machine the crank webs.

Cheers

Andrew

 

[Ghosty]

Hi All,

PROBLEM:- Getting small diameter cast iron round bar.

FIX:- Make your own.



I have some 40mm(1.575") round bar, cut length off of it, I have a 1mm(0.040") slitting saw, cut the round bar into quarters.

Pieces almost triangular, fit into 3 jaw and machine round.

Now have a piece almost 14.5mm(0.565") in dia, A lot less waste that machining the 40mm bar down to size, and I also have 4 pieces.

Now to make the pistons.

Cheers

Andrew

 

[Ghosty]

Hi All,

Up until now I have been making the parts for two engines. Now I will be working on just one engine at a time.

Started the most exacting part of the build. Started with lapping the cylinder, very messy part of the build.

Then machined and fitted the contra piston to the cylinder.

Then from the same blank, I machined the piston and then lapped for fit in cylinder, more mess.

Then cleaned in ultrasonic cleaner and then assembled complete engine.

We are almost there, now on to the starting bit before finishing the other engine.



Cheers

Andrew

 

[GailInNM]

Andrew,
Great build. I have a soft spot for the Mills as I flew on in a single channel escapement controlled radio control model in the late 1950's so it brings back memories.
I have also split cast iron stock in a manner similar to what you did. While I don't think it will affect your part, there is a problem with doing this on some parts. I appears that the continuous cast iron stock is softer or less dense in the center and gets progressively harder as you progress toward the OD. This has bitten me several times (slow learner !!).
First time was refurbishing the piston valve in a commercial Gauge 1 steam locomotive that was exhibiting the dreaded "Slide valve wear in and Piston valves wear out" syndrome and was leaking badly. The 4mm piston was stainless steel and was well made and showed n o signs of wear. The valve cylinder was part of the brass main cylinder casting and was well worn. Since there was plenty of meat to do so I decided to sleeve it with a cast iron liner. I reamed the casting to 5mm. After quartering a piece of cast iron stock, I turned the OD of the sleeves on all 4 pieces to a sliding fit in the reamed castings so they could be secured; with Loctite when finished. So far so good.
Chucking a sleeve in a collet in the lathe, the sleeve was center drilled, drilled and reamed to 0.0015 under size of the4mm required and then lapped to size with an adjustable brass lap, cleaning and checking for size often. I used the piston as plug gauge. When i made a final check the piston would enter the bore about 1/4 of the way on each end. Since I had quite a bit of experience lapping I knew I could easily detect any bell mouthing when lapping so I knew that was not the problem. I jammed it piston in the entry side and measured the run out. It measured close to zero both at the face of the sleeve and at the end of the piston. Repeating the test at the exit hole was very different. Near the face of the sleeve I had about 0.0015 TIR and the run out increased as I moved toward the end of the piston. This meant that the exit was no only not concentric, but was also coming out at a n angle. So I now kenew what the problem, but not what was causing it.
Rinse and repeat on a second sleeve with a new drill bit and I got the same results.
As I was out of ideas at this point I made up a small boring bar and after drilling a smaller hole I bored and lapped the two remaining sleeves an d they worked perfectly. So I moved on without knowing what was causing the problem.
Fast forward 5 years or so and I was building a small air cooled IC engine with a cast iron cylinder. The cylinder was mounted with 3 long 2-56 bolts that passed through the head and the 7/8" of fins and screwed into the cylinder mount. The 3 holes were drilled from the head end and the head test fit on the cylinder with the bolts, fitting perfectly. But, when I tried to screw it into the cylinder mount the bolts did not match the mount. After checking the mount I starting checking the cylinder. The holes at the head end were perfectly placed, but when measuring the holes at the mount I found them to be on a perfect bolt circle pattern, but the bolt circle diameter was 0.012" to small. Each hole had drifted inward toward the center by 0.006". It was then I realized that the small drills were being drawn toward the softer center of the bar. Easy to salvage the cylinder and most importantly I now knew what had been causing the problems 5 years in the past.
Gail

 

[Ghosty]

Gail,
I have found this with the cheaper grades of cast iron bar. Never had the problem with higher grades. you can tell the difference by the sound of the cuts, the cheaper grade starts out hard on tooling and is like machining alloy in the center, the better quality is the same right through.
Cheers
Andrew

 

[Ghosty]

Hi All,

Well after a little bit of playing around, "IT'S ALIVE", After about 20mins of runtime now it's swinging a 9x6wide blade with no problems.

Now on to the other engine.

Cheers

Andrew

 

[Ghosty]

Hi All,
Whats better than one engine running, how about in stereo, sorry no sound until 1:40min.
Cheers
Andrew

 

[Ghosty]

Hi All,
What is better than one engine running, how about in stereo.
Cheers
Andrew

 

[Ghosty]

Hi All,
And thus endith the build of these engines.
Now to build the planes for them.
Cheers
Andrew