HobbyKing.com New Products Flash Sale
Reply
Thread Tools
Old Mar 15, 2011, 02:51 PM
Registered User
Gluehand's Avatar
The windy west coast of Sweden
Joined Sep 2008
3,034 Posts
I just had to check it out....

A few years ago this Irvine Mills 75 was liberated from the attic of a retired hobby dealer who was selling off.....

It is still unused/untouched. The engine has yet to be "de-petrified".....in fact it is "factory petrified", as it was obviously run before leaving Irvine.

A quick ocular check for excentricity tells that...mm...yes, a little...
The hawk-eyed viewer will see that the crankshaft pokes just slightly upwards.

This divergence doesn't feel large enough to worry me though....I guess a thorough check of all old P/B diesels wouldn't leave us too many 100% true examples......in fact, judging by the outline of the casting doesn't tell us too much about the true angular precision - which may well be perfect internally....the eye may be mislead by the rough casting...it's the machining that counts...



Gluehand is offline Find More Posts by Gluehand
Last edited by Gluehand; Mar 15, 2011 at 03:42 PM.
Reply With Quote
Sign up now
to remove ads between posts
Old Mar 15, 2011, 03:53 PM
Registered User
JMP_blackfoot's Avatar
United States, OH, Galena
Joined Jul 2003
1,722 Posts
Quote:
Originally Posted by Gluehand View Post
...in fact, judging by the outline of the casting doesn't tell us too much about the true angular precision - which may well be perfect internally....the eye may be mislead by the rough casting...it's the machining that counts...
My thoughts exactly after now having seen three in this thread...
JMP_blackfoot is offline Find More Posts by JMP_blackfoot
Reply With Quote
Old Mar 15, 2011, 06:01 PM
Voices through wires? Ha!
Chas's Avatar
Joined Feb 2003
1,659 Posts
It isn't the symmetry of the crank in the casting that would worry me, rather that the liner will be out of whack with the piston. The liner seats on the casting, so if the crankshaft sits high it will alter the piston/liner timing. Perhaps 3/32" off center is "close enough".
Chas is offline Find More Posts by Chas
Reply With Quote
Old Mar 15, 2011, 06:26 PM
Registered User
Canada, ON, Hamilton
Joined Oct 2005
2,745 Posts
no kidding, just the facts

Chas, “My Irvine Mills also had an eccentric crankshaft but I don't think it helped any!” I thought you were just kidding! I was thinking about the previous post where the compression was set on the Ouragan using excentric crankshaft compression adjustment.
Now I see as I read on, our machining is a little off centre. Well, at least it’s not a square peg in a round hole!
When I was a kid I bought a “nice looking” Johnson .36. I could never start it. Later on I took it apart. I could see light between the piston and cylinder wall.
With this thread, everyone has certainly given enough information to write a small book.
For more comparisons:
Looking back for Mills diesels
page 22 post #324 CS replica
p17 #242
p11 #164
p3 #34 Doonside Mills
JohnAV8R is offline Find More Posts by JohnAV8R
Reply With Quote
Old Mar 15, 2011, 07:17 PM
Registered User
JMP_blackfoot's Avatar
United States, OH, Galena
Joined Jul 2003
1,722 Posts
An unusual PAW .09, with single rear exhaust and, I believe, a form of Schnuerle porting. It was developed for i/2A Goodyear racing, if memory serves right. Bought at Michael's Models around 1987.
JMP_blackfoot is offline Find More Posts by JMP_blackfoot
Reply With Quote
Old Mar 15, 2011, 08:03 PM
Voices through wires? Ha!
Chas's Avatar
Joined Feb 2003
1,659 Posts
No worries John, I know it's not that obvious (it escaped me in my fervorous lust at the model shop!) but I am sure it is detrimental to optimum performance on these engines. Like I said, can you imagine OS or Enya letting such an engine out of the gate?
Take the exhaust ports, drilled off line with each other...yes I know the originals were like that, but if you're going to make a modern replica do you have to faithfully reproduce the cock-ups? Yamaha made a copy of the Triumph Bonneville, but they didn't pre-drill the cover faces to accurately emulate the oil leaks; and my Pedersoli flintlock rifle conceals proper modern coil springs, thank goodness. I just think Irvine ballsed up a great project.
Chas is offline Find More Posts by Chas
Reply With Quote
Old Mar 16, 2011, 12:30 AM
Registered User
TLyttle's Avatar
Keremeos, BC Canada
Joined Mar 2004
2,639 Posts
"... but they didn't predrill the cover faces to accurate emulate the oil leaks;..."!! Stop it, Chas! I just spilled beer in my lap!!!
TLyttle is offline Find More Posts by TLyttle
Reply With Quote
Old Mar 16, 2011, 04:16 AM
Registered User
Gluehand's Avatar
The windy west coast of Sweden
Joined Sep 2008
3,034 Posts
Quote:
Originally Posted by Chas View Post
It isn't the symmetry of the crank in the casting that would worry me, rather that the liner will be out of whack with the piston. The liner seats on the casting, so if the crankshaft sits high it will alter the piston/liner timing. Perhaps 3/32" off center is "close enough".
Yeah... ....and maybe...

See the rough scetch below.
If the "figure" of red lines has true angles & dimensions, all is well, no matter if the casting looks like a potato......it's the guy in the machine shop that may mess things up a friday afternoon....

The A/A distance is, as you say, critical for port timing, and experience tells that some engines are more critical than others in this respect (on some examples, particularily small engines, even the thickness of the cyl.foot gasket will affect the function), while certain engines don't seem to get upset whatever we do.... (it's not magic, but closely related...)

So, a rough casting may make us suspicious at first glance, but it doesn't have to be that bad after all....


Gluehand is offline Find More Posts by Gluehand
Last edited by Gluehand; Mar 16, 2011 at 05:07 AM.
Reply With Quote
Old Mar 16, 2011, 01:20 PM
Voices through wires? Ha!
Chas's Avatar
Joined Feb 2003
1,659 Posts
I wouldn't mind a potato-shaped crankcase casting Gluehand....I could then build a replica of the Soviet "Commutater", and fool the e-power guys at the field...but frankly I can only see that you have confirmed what I said, that because the liner seats on a fixed point on the crankcase, it follows that any inaccuracy in the crankshaft position will alter the timing. Apart from looking like an Irvine copy of an Aurora.
Chas is offline Find More Posts by Chas
Reply With Quote
Old Mar 16, 2011, 01:33 PM
Registered User
JMP_blackfoot's Avatar
United States, OH, Galena
Joined Jul 2003
1,722 Posts
Quote:
Originally Posted by Chas View Post
...but frankly I can only see that you have confirmed what I said, that because the liner seats on a fixed point on the crankcase, it follows that any inaccuracy in the crankshaft position will alter the timing...
Inaccuracy in the crankshaft position relative to what exactly?
The "fixed point in the crankcase" is another machined surface. As such, it is the distance and squareness between this machined surface and the crankshaft bore which matter. Now, where is the reference from which all the rest was machined? The bottom of the mounting lugs?
JMP_blackfoot is offline Find More Posts by JMP_blackfoot
Reply With Quote
Old Mar 16, 2011, 01:45 PM
Voices through wires? Ha!
Chas's Avatar
Joined Feb 2003
1,659 Posts
The top of the casting where the liner flange seats, JMP. Does the machinist compensate for the out-of-whack crankshaft when setting this up? Doubt it.

If, as Gluehand calls it, the A-A distance is correct, then all should be well - but my own Mills ran as testament that they could not be bothered to get it right.
Chas is offline Find More Posts by Chas
Last edited by Chas; Mar 16, 2011 at 01:52 PM.
Reply With Quote
Old Mar 16, 2011, 02:45 PM
Registered User
Gluehand's Avatar
The windy west coast of Sweden
Joined Sep 2008
3,034 Posts
Mind, this is a non-expert thinking out loud...

When machining a crankcase casting, the most obvious starting point would be the crankshaft bore....

This done, next step would be milling the external mating surfaces.
If the milling jig consists of a mandrel (is this the correct term?), fitting into the newly made crankcase bore, the angularity and distances (e.g. A/A) would be perfectly true....even though the initial crankcase bore is slightly non-linear to the casting.....or in case of the proverbial potato...

So far so good...with a proper jig setup all should be well, the function of this engine would be perfect, even though the shaft appears to poke in some direction, related to the crankcase, as the shaft bore is the reference to the entire geometry...

However a poor/worn jig, or a poor basic setup of same, would obviously upset all good intentions...


Gluehand is offline Find More Posts by Gluehand
Last edited by Gluehand; Mar 16, 2011 at 02:55 PM.
Reply With Quote
Old Mar 16, 2011, 03:06 PM
Voices through wires? Ha!
Chas's Avatar
Joined Feb 2003
1,659 Posts
Yep, that's all fine GH - but IF my Auntie had knackers she'd be my Uncle. My Mills was as flat as the proverbial (and the liner had never been touched, so if it was backwards it came that way from the factory). I would certainly buy one of the later, CNC models, and my 1.3 is super, but I think there are some turkeys in that first clutch.
Chas is offline Find More Posts by Chas
Reply With Quote
Old Mar 16, 2011, 07:53 PM
Registered User
Joined Aug 2007
1,503 Posts
Hi

Can you really start them with no ether fuel and an electric starter as in You tube ????? Ive never tried

Just kero and castor ?
NX-687 is online now Find More Posts by NX-687
Reply With Quote
Old Mar 16, 2011, 08:06 PM
Registered User
Joined Aug 2007
1,503 Posts
Then again

I like the gooey mess and bleeding fingers and swearing to get my worn out silver swallow to run and then the wind blows it in on the lines and wrecks the model and the fuel tank leaks fuel in my car
NX-687 is online now Find More Posts by NX-687
Reply With Quote
Reply


Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Discussion Need help with two diesel engines ! cosmin Engines 4 Apr 18, 2014 08:18 PM
Diesel Engines Aeromister Engines 8 Sep 01, 2009 08:17 AM
WTB-Model Diesel Fuel slogo Aircraft - Fuel - Airplanes (FS/W) 3 Nov 13, 2004 10:42 PM
scale model of engines dw1122 Life, The Universe, and Politics 2 Apr 23, 2004 06:43 AM
diesel engines wyflyer_55 Fuel Plane Talk 7 Apr 22, 2002 03:45 AM