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the Daily hi thread
Jim Tyler Article 'Crush test Dummy'
- Thread starter Backgardenplinker
- Start date
Mike Woody Watkins
Member Extraordinaire
I met Jim a while back in his workshop that features in his articles. Really nice chap and very interesting. We had a great morning.
That’s not me, it’s my good friend and fellow member 1311mikeg.
That’s not me, it’s my good friend and fellow member 1311mikeg.
Meal Dot
Member Extraordinaire
The bloke is a hero for springer types. About the only reason I read any of the weak-kneed airgun rags. Properly investigates the issues around jumpy pellet chuckers. Good man! 
Vangard
Member Extraordinaire
I liked to read Jim's articles in the airgun mags. He realy knows his stuff.
1260engineer
Member Extraordinaire
Im going to be the stick in the mud here .
This is a totally pointless
the reason being. in the cylinder the piston seal is constrained by the cylinder walls .which means any measurements outside of the cylinder are ...
for a true reading to check any seal compression . the seal would need to be put in a short ring cylinder and the gauge would be set on the tail stock not the seal.
then you have another problem. the seal material now contained with nowhere to expand becomes a soild in the confined space.
Ive personally been through this yonks ago when i first started making seals .
part of work out the relief behind the sealing edge . the seal on the piston is placed in a dummy cylinder end then i compress. then im able to run a feeler gauge around the rear edge of the seal . to make sure i had clearance.
this is done to make sure as the seal starts to build pressure the seal body does not introduce drag to the cylinder wall .
This is a totally pointless
the reason being. in the cylinder the piston seal is constrained by the cylinder walls .which means any measurements outside of the cylinder are ...
for a true reading to check any seal compression . the seal would need to be put in a short ring cylinder and the gauge would be set on the tail stock not the seal.
then you have another problem. the seal material now contained with nowhere to expand becomes a soild in the confined space.
Ive personally been through this yonks ago when i first started making seals .
part of work out the relief behind the sealing edge . the seal on the piston is placed in a dummy cylinder end then i compress. then im able to run a feeler gauge around the rear edge of the seal . to make sure i had clearance.
this is done to make sure as the seal starts to build pressure the seal body does not introduce drag to the cylinder wall .
@1260engineer - I did precisely what you suggest using a TX piston and cylinder. The reason I measured the unconstrained seal diameter under compression first was to be able to compare the difference in the axial compression when the seal couldn't expand sideways, and it was significant. This was of no immediate benefit, but added to our knowledge at a time (ten years ago) when we knew diddly squat about the subject.
Two months later, I published a follow-on article describing how I measured the kinetic friction of the seal as it travelled up the cylinder and the air pressure increased. Perhaps @Backgardenplinker might have that one?
Two months later, I published a follow-on article describing how I measured the kinetic friction of the seal as it travelled up the cylinder and the air pressure increased. Perhaps @Backgardenplinker might have that one?
Backgardenplinker
Member Extraordinaire
1260engineer
Member Extraordinaire
Hi Jim .Warning before doing experiments always check out the workshop window for blokes in white coats
Most folks think us blokes spending hours and hours in sheds and workshops doing this stuff are nuts .
Im playing with a strange idea at the moment to do with piston bounce and the piston seal .
Tiz something i came across by accident 30 odd years ago making my seals .
But now seeing what was happening on with the oscilloscope. Im now chasing that accident to see if i can turn it into something.
1260engineer
Member Extraordinaire
Cheer mateI will have a look through the folder today and see if i can find it
chouchin66
Top Tier member
Since we're on about seals...
In an irregular bore would leather perform to better efficiency than a synthetic counterpart ? Better ability ( withhold a rotating piston) to conform to an out of round condition ? How much more efficient is synthetic vs. leather ?... Hydraulic rams & water pumps still use leather seals... Inquiring minds.
In an irregular bore would leather perform to better efficiency than a synthetic counterpart ? Better ability ( withhold a rotating piston) to conform to an out of round condition ? How much more efficient is synthetic vs. leather ?... Hydraulic rams & water pumps still use leather seals... Inquiring minds.
You're absolutely right to look for precedents before wasting time, of course, but in experimental engineering it's best practice to measure whatever you can whenever you can; sometimes it comes in very useful, other times less so.
Warning before doing experiments always check out the workshop window for blokes in white coats
Most folks think us blokes spending hours and hours in sheds and workshops doing this stuff are nuts .
Im playing with a strange idea at the moment to do with piston bounce and the piston seal .
Tiz something i came across by accident 30 odd years ago making my seals .
But now seeing what was happening on with the oscilloscope. Im now chasing that accident to see if i can turn it into something.
Backgardenplinker
Member Extraordinaire
I found a few more of Jim's articles on piston seals which i will make new posts for. Hopefully the one in question @1260engineer & @JimPlas
As you can see i have plenty here including a number from Mike Wright. Some may not be complete or muddled.
As you can see i have plenty here including a number from Mike Wright. Some may not be complete or muddled.
1260engineer
Member Extraordinaire
Mike Woody Watkins
Member Extraordinaire
@Backgardenplinker ‘s complete set of Airgun World magazines compliments his comprehensive collection of carpet slippers and beer tinsYou need to get out more mate your playing card are starting to smerk
!
chouchin66
Top Tier member
I availed myself of the Readly app..." flipped through" years worth of back issues, specifically to read Jim's tech.articles...well worth the price of admission & zero shelf space required.