Lionel 622 doubleheaded with 675?

[IDM1991]

I ran our 675 "K4" at the head-end of a ten-car freight train (two modern ore cars, ten postwar cars, all with die-cast trucks), with the 622 NW2 switcher providing additional power immediately behind.  I tried this for three reasons:

1) Pulling power.  I often run a 2343 F3 "A" unit, and its two motors make for some spectacular pulling power.  I reasoned that the two single motors in the 675 and 622 would have a similar effect.

2) Traction.  The 675 doesn't have Magne-Traction, which the 622 does.  I figured that the combination of Magne-Traction in the latter (which I've been running in reverse - that is, "cab-forward" - for these doubleheading exercises), when combined with the heavy metal construction of the former, would aid in traction.  Previous experience (which resulted in a broken classification lamp) has taught me to never run the 675 by itself on my outer 031 loop without a Magne-Traction equipped locomotive somewhere in the consist.

3) Prototypical practice.  Out of deference to some steam-to-diesel and modern-day practices, I figured running a steam locomotive and diesel switcher up front would look rather interesting.

I generally use the 622 for very basic switching and as a helper engine slotted into the middle of long (nine or ten-car) trains headed by an MPC-era CPR SD24.  My question: is this doubleheading wise, or would it be too hard on the locomotives in question? 

[sir james I]

I don't see a problem as long the two engines run somewhat close to the same speed. The 622 is probably slower but the 675 is geared different and can probably handle a little push/pull.

[lionelsoni]

Speed compatibility is not likely an issue when both locomotives have series-connected (universal) motors, as these do.

When, at any particular track voltage, two permanent-magnet motors (like the "can" motors in modern toy locomotives) want to run at different speeds, the motors will fight each other.  The slower one can actually produce a negative torque to slow down the faster one.  Series motors never do this, even if the motor speeds are very different.  The worst that can happen with mismatched series motors is that the double-heading doesn't produce any benefit; but even that is unlikely.  

[sir james I]

Bob is the forum expert but I still prefer to run engines that are close to the same speed.