Is the LMS forward closure supposed to have an o-ring in the grove

SpaceX76

Well-Known Member
Joined
Jan 28, 2020
Messages
59
Reaction score
24
Location
Northern New Mexico
I am assembling my first LMS motor and noticed that there is a grove in the forward closure that looks likes it's for an o ring. I looked at the diagrams provided with the instructions and it looks like there is an o ring in the grove. However in both of the LMS kits that I purchased there are no o rings that fit that grove.
 

rcktnut

Well-Known Member
Joined
Oct 26, 2009
Messages
1,931
Reaction score
521
Location
Sheboygan WI
All the LMS motors assemble basically the same way. Never had any but having an O-ring on the outside of the forward closure assembly would be useless/ not needed although in the instructions the red ring around the bottom most groove looks like an O-ring. The epoxy should seal everything up, and the way the forward closure is assembled if there was an o-ring it would get all "smucked" up with epoxy and would not function like it should anyway. Post your question in the Aerotech thread, but I would say no o-ring needed.
 

AeroTech

Well-Known Member
TRF Supporter
Joined
Dec 17, 2009
Messages
1,111
Reaction score
2,823
The ‘F’ LMS were discontinued. The O-ring groove is an artifact of an earlier motor design where we were hoping to reuse the casing several times (“limited use RMS”). When everything worked correctly, we could get three or four firings out of a casing. However, we had occasional problems getting the O-ring to remain in the groove when the forward bulkhead was installed, so the idea was abandoned.
 

Tractionengines

Well-Known Member
TRF Supporter
Joined
Aug 29, 2020
Messages
802
Reaction score
750
Location
Northeast Ohio
AeroTech, THANK YOU for the explanation. It is so nice that you give us more than just a Yes/No answer. It helps us detail oriented types, fill in the blanks, about what we "see" and what we are "told".

Mike.
 

dpower

Well-Known Member
Joined
Jan 18, 2009
Messages
1,692
Reaction score
386
I miss the LMS motors, I like to fly the F27, but usually need a -6 delay, so the LMS F27-8 was great for that, just drill a couple seconds off before assembly.
 
Top