Hi Guys,
For those interested,I provide a follow on to a previous post of mine
re. the difference between the various models of the OS Max H 40. I
found some old engine tests done by Peter Chinn-in Aeromodeller dated
Jan. 1971 he tested the dedicated H40-S,and it differs from the R/C
version in timing(open at 45 degrees ABDC,closes at 40 ATDC=induction
period of 175 degrees compared to 180 for the 40-SP and 195 for 40-R
the transfer & exhaust periods a modest 105 & 125 compared to 120 and
142 degrees for the 40-R). The combustion chamber shape,unlike the
high compression wedge type of the 40-P and 40-R,is a shallow type of
hemispherical as on the 40-SP R/C,but with a lower compression ratio.
The effective venturi choke area is quoted as 15.8 sq.mm. which is
roughly only one quarter that of the hot 40-R. The 2 hotter models
(40-P & 40-R)came with twin ball races,whilst the normal R/C 40-SP
and the C/L 40-S had a single rear race with a bronze front bush.
The 40-P had a single Dykes ring,the stunt version a single compression ring and the normal R/C had 2 rings. Hope this helps.
For those interested,I provide a follow on to a previous post of mine
re. the difference between the various models of the OS Max H 40. I
found some old engine tests done by Peter Chinn-in Aeromodeller dated
Jan. 1971 he tested the dedicated H40-S,and it differs from the R/C
version in timing(open at 45 degrees ABDC,closes at 40 ATDC=induction
period of 175 degrees compared to 180 for the 40-SP and 195 for 40-R
the transfer & exhaust periods a modest 105 & 125 compared to 120 and
142 degrees for the 40-R). The combustion chamber shape,unlike the
high compression wedge type of the 40-P and 40-R,is a shallow type of
hemispherical as on the 40-SP R/C,but with a lower compression ratio.
The effective venturi choke area is quoted as 15.8 sq.mm. which is
roughly only one quarter that of the hot 40-R. The 2 hotter models
(40-P & 40-R)came with twin ball races,whilst the normal R/C 40-SP
and the C/L 40-S had a single rear race with a bronze front bush.
The 40-P had a single Dykes ring,the stunt version a single compression ring and the normal R/C had 2 rings. Hope this helps.
RetredNed
Bob Allen