Together with his brother Ernst he founded Hirth Motoren, which we will see in another chapter. It seems that they made some engines just before or at the time that they started their motor activities with the famous HM-60. In the early 1920's. See Hirth.

“H. Hirth engine”

-It is a two-stroke radial engine, rather a cross one. Each cylinder group had two cylinders linked by their combustion chamber. Admission was made through the base of one cylinder and the exhaust through the base of the other.

"Double cylinder principle"

-As we see, the weight of the double connecting rod and piston required a counterweighted crankshaft.

-Here in Spain this operation principle we saw in the Italian "Iso" motorcycle engines, which were built here under license as well. At the Musée de l'Air et de l'Espace in Paris there is a sectioned engine with this system.