Hydraulic Torque Converter

[HoHun]

Hi everyone,

Here's a bit of information on torque converters similar to those used in the WW2 Daimler-Benz and in the late production Allison V-1710 aero engines.

Cut-away picture of a modern automotive torque converter:

http://www.kfz-tech.de/Programme/GGBild.htm?Bilder_Kfz-Technik_KupplungWandler_Drehmomentwandler04.jpg

The entire device of course is filled with hydraulic oil in a working example :-)

Red: Driving wheel (integral with casing)
Blue: Driven turbine
Bare metal between red/blue wheels: Deflection wheel (can only turn in one direction due to ratchet, free-wheeling in that direction)
Green: Direct drive (not implemented in WW2 aero application)

Small version of the picture with German explanation:

http://www.kfz-tech.de/Drehmomentwandler.htm

Hydrodynamic clutch (no torque-conversion capability):

http://www.kfz-tech.de/Programme/GGBild.htm?Bilder_Kfz-Technik_KupplungWandler/HydrKupplung03.jpg

With explanation:

http://www.kfz-tech.de/HydraulischeKupplung.htm

Another site with pictures and German explanation:

http://www.luk.de/content/de/products/productinformation/gearing-systems/automatic-gearing/converter_sv/HydraulischeDrehmomentwandler_lv.jsp

Schematics:

http://hometown.aol.de/HoHunKhan/Drehmomentwandler2.jpg

By the way, if you are American, chances are high are that you are the proud owner of such a neat hydraulic torque converter! It's an important part of your car's automatic transmission :-)

The "green" direct drive (lock-up) part is a concession to economic operation, as far as I know it was absent from WW2 supercharger drives because only a fraction of the engine power was routed through the hydraulic converter, and only about 2% of that fraction was lost to hydraulic "slip", so it wasn't worth the additional complication.

In automotive or gas turbine power plant applications, all of the power is routed through the torque converter, so a lock-up eliminating the slip once high rpm is reached is a very useful feature for improving efficiency there.

Regards,

Henning (HoHun)

[BPNZ]

Hi Hohun,

Thanks for the links

I have often wondered why a lockup device was not included on the DB supercharger drives.   It would have given some advantages (slightly more power) above full throttle height and probably reduced oil temperature at high altitude.   I understand this was a problem in the 601 series (high oil temp).

Oops I see you answered this

I still think it would have been a good idea up to the 605Ds.


Regards
Brian

[Charge]

I'm not sure if 2% more power would be significant if it would bring other issues with it. What if the lock would jam? The engine would blow to pieces in sudden dive. Just one more potential failure into an already complicated design.

The oil temp was a problem which was cured to some degree but AFAIK the pressure was prone to be quite low and this was a problem which was never completely solved. Even some sort of de-areators were tried but that did not cure the slightly too low oil pressure.
Not sure if this ever was a true issue of concern for 109 jocks.

Nice info HoHun.

-C+

[HoHun]

Hi Charge,

>I'm not sure if 2% more power would be significant if it would bring other issues with it.

Well, it's not even 2% more power - it's 2% more of what is spent on the supercharger. So if the supercharger might require for example 300 HP (which might be in the ballpark), a lock-up would recover just 6 HP.

>Even some sort of de-areators were tried but that did not cure the slightly too low oil pressure.

I'm not sure the de-aerators were tried in conjunction with the hydraulic clutch - I seem to remember something about engine oil.

Regards,

Henning (HoHun)

[Charge]

Sorry HoHun, I was not clear on this. I didn't mean the de-aerator had anything to do with supercharger clutching. Just that DBs had oil pressure problems and that was one possible cure recommended by DB designers which didn't work after all.

-C+