Mitchell B-25
Paralleling the Engines

An illustrated guide on how to align a multi-engine model.

Click on Thumbnails

#1 - Use a vertical surface that is flat in a 4' length & vertically level for 2'. Place the fuselage 90 to the wall.

#2 - Measure the distance from the wall to the end of each engine crankshaft. This distance MUST be the same.

Anchor the plane so it does not move. The plane can be any distance you want from the wall to the crankshaft as long as both measurements are the same.

Put both propellers horizontal, the same way.

#3 - Measure the distance from the wall to the tip of the propeller keeping the tape measure 90 to the wall & prop tip. Make sure you use the same location on both tips of the prop on each engine for your measurement.


#4 - Record each measurement for each engine prop tip.

#5 - For each engine, subtract the smaller distance from the larger prop tip distance.
   Engine A = 18 13/16 - 18 1/2 = 5/16
   Divide 5/16 by 2 = 5/32
   Move the left tip forward 5/32 & the right tip 5/32 back. This puts both prop tips
18 21/32 from the wall. To accomplish this, I needed to shim the left side of the engine mount forward .039. Do the same for the other engine (B). My engine "B" was shimmed .033 on the left side of the engine mount.

#6 - Now both engine prop tips are 18 21/32 & parallel to each other.

#7 - NOTE: There is a bit of debate about offset. Some builders put both engines with some offset such as 1 to the side and 1 down or many combinations therof. I personally like my engines on multi-engine aircraft 0 & 0, just my preference.
NEXT: Engine Testing at Ash Creek Field
Back to B-25 Page  Back to Home

Search this Web Site