True to scale engines ?

[lawqbarr]

This thread is provoked by the discussion of the accuracy, or inaccuracy, of the Mercedes DIII engine offered with the Eduard W-4 which appears in Bughunter's latest build

To state the obvious --- Real engines have fixed dimensions

To keep matters simple,  please, let's just concentrate on gross dimensions such as length and width of block casting, circumference of cylinders at their thickest point, spacing between cylinder centres  etc ...   Details such as the length of the propeller mount/ extension of the crankshaft or other projections mounted at the rear of the camshaft or the mounting plates at the base of the block can of course be derived from the gross dimensions of the major components.
 
So, if we just forget "scale drawings" for present purposes ... Just how long in mm should a Mercedes 150 160 180 or Austro-Daimlier 200 engine really be in 1/48 or 1/32 scale ?

Many of us have noticed and commented on the fact that some kit engines are, or appear to be, decidedly "under-nourished".

No doubt a kit manufacturer might have to do some fiddling/ "down-sizing"  to achieve the fit of an kit engine where the real aircraft has a very closely cowled motor, but some kit engines clearly take that to an extreme so that  what's supplied is significantly ( and noticeably) under-sized .

Has anyone on this list or elsewhere ever done a comparison between 1:1 engines and the available kit and after-market in-line engines to  produce a guide as to the most dimensionally accurate options for each of the main types of WW1 in-line aero engines ?

Small Stuff have done a great job cleaning up both accuracy and detail with their terrific range of rotary engines but the ranks of most kit and after-market in-line engines are still in a bit of disarray

Any feed back gratefully received

PS does anyone do the Austro-Hungarian  Hiero 150 in 1/48 that is currently available ?

Regards to all
David 

[Bughunter]

At first thanks for mention my build
I'm not sure if I mentioned it in the build report:
I found a drawing on theaerodrome.com "from Fokker archives":


With the exact size of the mounting positions you can check your engine replication.

A polish museum has a huge digital archive, free accessible over the internet (but with a watermark on the scan, but that is ok for me). A lot of engine manuals are part of the archive, but I'm not sure about dimensions.
https://www.muzeumlotnictwa.pl/digitalizacja_archiwaliow/digitalizacja.php

Cheers,
Frank

[kensar]

I don't know of any such list of accuracy of engines made by different manufacturers.  Being dimensionally accurate is one thing, but the rest of the airframe needs to be dimentionally correct also for it to fit, which doesn't happen often.  So, in the end, it seems to me that you just need to get an engine that fits in the airframe you have (or build one that fits the engine you have).

[RLWP]

Because they are made to fit into models with over scale thickness panelling, chances are many model engines are undersized

Richard

[RAGIII]

Because they are made to fit into models with over scale thickness panelling, chances are many model engines are undersized

Richard

Some after Market engines are close like Taurus Models Rotary Engines. That is why they rarely fit in the kit cowlings 
RAGIII

[lawqbarr]

Thanks to each of Bughunter and RAGII for their responses

Using Bughunter's Fokker drawing it appears the overall length of a Mercedes engine in 1:1 is c. 1338mm ( I'm cutting off about 200 mm in 1:1 for the thickness of the prop and its boss )
 
That measurement converts (using this marvelous tool - http://www.scalemodelersworld.com/online-scale-converter-tool.html ) to c. 27.875 mm in 1/48.  Nearly all kit supplied engines are quite a lot smaller than that.

RAGII's right of course,  most accurately true-to-scale engines won't fit inside the thickened walls of a plastic kit's fuselage or cowling ...
but that fact doesn't justify fitting an exposed engine that's significantly undersized just because it was supplied with the kit

If you're doing an aircraft with a fully cowled engine then, of course,  the above is taking AMS to a completely silly degree - But if you do aircraft which were built or often flown with fully or substantially exposed engines, don't you want something that is as close to scale as possible  ?

In part answer to my own question about the Hiero 200 hp engine -
There's no after-market option I can identify - One of our Austrian modeller friends (Peter Plattner) was going to produce a 185 and 200 Hiero a few years back, but, to the best of my knowledge, that never happened.
 
The only kit I know of which supplies this engine is the Special Hobby or Blue Max Phonix DI/ DII

Regards to all and thanks again to Bughunter and RAGII
David