PD Malfunction Story

[fleegs]

Thought I would pass this on because I am amazed at what solved it.

I bought an aluminum PD-S from a CPF member (Don had built it). I received the light and it worked not as great as I would have liked. When turning it on, the low would come on then go off then come on. But the second time it came on it was so close to the high that it would be hard to get it to stay on low. But the first low would sometimes go out if left there. Plus turning it off and making sure it was off and not between the lows was a pain. Since I picked the light up on the way to work I was messing with it at work. I went to adjust the Kilroy and it broke right off. Which Don mentioned to me he has never seen. Just my luck I am the first. Anyhoo, the light didn't even make it home before I broke it (hence the picked it up on the way to work comment). Well, Don being awesome and slightly skeptical that I broke the Kilroy off nana had me send it in for repair and only charged me shipping. What a guy! :thumbsup: Continuing on, I got the light back and it continued to do the low off low high thing. I was amazed I thought this would have been fixed by the repair. No matter how I adjusted the kilroy, down, up- it did not solve the problem. To skip a lot of things I tried to save typing...I started switching parts (piston, head...) with another PD I have. I narrowed it down to the body of the PD-S light. What the heck I thought. How could it be the body? So you know what I did to fix it and have it work just like my other PD (very smooth transition between low and high with only off, low, high)?

Pause. Enter all guesses now. End Pause.

I put scotch tape (only tape I have currently) around the piston to tighten it up in the body of the flashlight. The light works beautifully now. I still can't believe it. The piston must have been tilting making intermittent contact with the kilroy. But it was so reproducible.

I hope you enjoyed my story. I am so glad to have a smoothly working PD-S now. Even if it needs scotch tape to make it work! :candle:

rob

 

[mspeterson]

One of my PD's acted as you described when I first got it. I tried the head on a different, perfectly functioning PD body, and the head was fine. I noticed that the spring in the piston was shorter on the malfunctioning PD. When I switched the cut down spring for a full lenght replacement, the light worked like a charm. Don started cutting the piston spring to make the light easier to operate, IIRC, but I prefer it stiffer. My malfunctioning PD's spring was cut about 1.25 twists more than the spring cut by Don (which worked flawlessly from the moment I got it, BTW & FWIW!!)

The biggest problem I have had with my PD is when it died on me, wouldn't turn back on....long story short....Yep, the battery!!!

Were you using a crow bar on poor Kilroy?:nana:

 

[fleegs]

I have been working out.

That made me laugh. Nice one. Least I am first at something.

rob

 

[Oddjob]

I did the same thing. When I first got my PD-S I heard and felt kind of a clicking when using the piston for mometary high from having it on low. Both levels always worked but there wasn't a smooth piston push. After a few minutes I deduced that the piston was not perfectly aligned to push the kilory. I took the piston out and wrapped some tape around it near the opening. After putting it back in, the piston was centred in the body tube and was contacting kilroy properly. Voila no clicking.

 

[Kiessling]

The little clicks don't disturb me. Then again, the lights do work regardless.

 

[Codeman]

The clicks don't really bother me either, but I am tempted to put some teflon tape on my Ti-PD-S, as it clicks more than my other PD's.

 

[Aepoc]

Interesting...

It seems I have the opposite probem. Sometimes I apply too much nyo-gel to the o-ring on the piston. When I do this the excess gel goes between the body and piston causing the piston to stick... sometimes I will use the momentary and it will stay on longer then the time I have my finger on the piston. I have heard of some people just using a different lube for the piston o-ring. Not sure how this works but I know if I just use less lube then the PD works like new.

Thanks for the story

 

[Kiessling]

Nyogel gets sticky over time. It works well with Surefires, but the PD doesn't love it as much. There are quite some threads in this forum about lube (ahem), and there are several great options.
The obvious is Krytox 50/50 from the Shoppe which is the stuff Don uses originally on the lights. Teflon tape is another favourite.
bernie

 

[greenLED]

I solved the clicking "issue" by unscrewing the head a bit. Somehow that allows the piston to be aligned better. You could also extend the kilroy a tiny little bit outwards.

 

[McGizmo]

These lights aren't perfect by any stretch and the issues discussed here are good case in point. If I could sum up the nature of these underlying issues I would categorize the problem as based on guidance VS friction or free contact VS binding.

The function of the PD would have been easier to control and more consistent had I started with a larger diameter on the outside and worked my way in allowing more wall thickness to components and included some type of guide bushing on the front end of the piston, holding it to a tighter concentricity relative to the other components. The point is moot though since the light is what it is. There is a critical ring with an ID and OD dictated by designed dimensions and then subject to tolerance variations among the parts. Within this ring, the lip of the piston needs to reside as well as Kilroy's nose and the contact ring surrounding it. The front end of the piston as well as the contact ring and Kilroy need to have free room and clearance to advance and retreat within the sleeve without binding contact in the case of the piston and any contact what so ever with Kilroy and the contact ring made against the sleeve. The components need room for movement but not too much room that they can get sloppy and out of alignment with eachother.

When the piston is depressed to the point of contact with Kilroy and then further to make contact with the contact ring itself, the force against kilroy has an off axial vector which results in a bit of a side load transfered among the head, piston and sleeve. I believe this load varies among the lights and even from one activation to another on the same light. It is allowed room to express itself due to the float in the front end of the piston as well as to a lesser extent, the side play in the threads of the head to sleeve mate. I believe that it is possible in some cases for Kilroy to even pop into the interior bore of the piston lip. This can't be witnessed on a light because of where and when it takes place. I have been flattening Kilroy's nose to keep it from making undue contact with the threads when the head is installed on the sleeve but in doing so, I also increase the potential for Kilroy to not stick out far enough for optimal contact with the piston lip. I know what I am trying to convey here but no idea if I am being successful in getting the relationships of thesse parts across.

If I felt I had to rely on a teflon bandaid to insure proper function, I would go back to the design board but I have not deemed this to be the case. None the less, the teflon wrap on the front end of the piston makes a marked improvement on all of the lights I have tried it on. In the case of Fleeg's light here, I believe Kilroy can be further tweaked to bring proper function to the light without the need to restrict the off axis slop of the front end of the piston however Fleeg's fix is likely a better solution in terms of function as it directly addresses the weakness inherent in the design itself.

I am sorry that I didn't catch any intermittant issues in Fleeg's light when I had it in for repair. I will be happy to take it in again and make certain that its functionality has been rectified should Fleeg opt to go this route. In general and the vast majority of cases, the weakness described above is there but not to the extent of manifesting itself in a malfunction. There were sloppier tolerances in the Al PD's and in some cases a greater likelihood of mating parts actually getting outside of the critical ring mentioned above. Aside from a number of the lights audibly clicking when one goes from low to high but without failure of the light functioning properly, this case reported here is the first of its kind to my memory and knowledge.

Forgive the long ramble here but I wanted to let you guys know that I am not indiferent to these lights and their function and I wish to think myself reasonably versed in their function as well as weaknesses. When I state that these lights aren't perfect, I do mean it!

I should state as well though that I expect proper function despite imperfections and shortcomings in the design.

 

[Codeman]

... I know what I am trying to convey here but no idea if I am being successful in getting the relationships of thesse parts across.
...

Made perfect sense to me, though that may be of little comfort!

Seriously, the tolerances you'd probably need to eliminate the click might also add some friction, and certainly some cost.

 

[greenLED]

I know what I am trying to convey here but no idea if I am being successful in getting the relationships of thesse parts across.

I didn't know McGizmo spoke Chinese. :nana:

Actually, it all made perfect sense.

 

[PoliceScannerMan]

*Note to self, read this thread later* :thinking:

 

[Codeman]

If anyone thinks about using teflon tape to stop the clickies, don't bother. Unless you apply something to hold it in place, it simply slides up and down the piston - duh.

I think I'll keep my clicky!

 

[Oddjob]

When I first got my PD-S and was fiddling with I just used the first tape that was in my reach which was some half inch wide masking tape. I thought I would just use it to see if it eliminated the clicking and that I would find a more suitable tape later on. I just wrapped it once around and believe it or not six months later the piston is still working fine. I do put a tiny bit of lube on the tape when I lube the O-ring. Its a pretty low tech fix I know but I figured why bother changing it when it is still working.

 

[fleegs]

Hello. Thanks for the offer Don, I do not plan on sending my light in. I am very happy with the light, the person who sold me the light and the maker of the light. It now works great. I just wanted to share the story because the fix is so easy. My light did click and taping the psiton stopped it. I did not care about the click for some reason so I never mentioned it. I assumed the click was the piston "bouncing" over the first thread. I could control it somewhat with how I pushed on the piston.



Enjoy your lights!

rob

 

[:)>]

*Note to self, read this thread later* :thinking:

+1

When Don starts talking about stuff like "off axial vectors", then I need to go away, drink some caffeine and bring back a dictionary.

 

[Hodsta]

+1

When Don starts talking about stuff like "off axial vectors", then I need to go away, drink some caffeine and bring back a dictionary.

Ok, you are walking down a crowded highstreet with the single aim of getting to your favourate bar, which is directly ahead of you. This is your axis.

You are accompanied by your loving wife who spots a shoe shop on the right hand side of the road - totally off your axis.

The interaction between the conflicting requirement for beer versus shoes can create a vector or force.

If this vector is strong enough it may cause a diversion off axis resulting in a failure at the mouth/beer interface (analagous to that of the kilroy/piston). This can generally be avoided by the liberal application of tape prior to any shopping trip.

 

[Oddjob]

Ok, you are walking down a crowded highstreet with the single aim of getting to your favourate bar, which is directly ahead of you. This is your axis.

You are accompanied by your loving wife who spots a shoe shop on the right hand side of the road - totally off your axis.

The interaction between the conflicting requirement for beer versus shoes can create a vector or force.

If this vector is strong enough it may cause a diversion off axis resulting in a failure at the mouth/beer interface (analagous to that of the kilroy/piston). This can generally be avoided by the liberal application of tape prior to any shopping trip.

I love analogies. I use these kinds all the time to explain things. Well put!

 

[matrixshaman]

Ok, you are walking down a crowded highstreet with the single aim of getting to your favourate bar, which is directly ahead of you. This is your axis.

You are accompanied by your loving wife who spots a shoe shop on the right hand side of the road - totally off your axis.

The interaction between the conflicting requirement for beer versus shoes can create a vector or force.

If this vector is strong enough it may cause a diversion off axis resulting in a failure at the mouth/beer interface (analagous to that of the kilroy/piston). This can generally be avoided by the liberal application of tape prior to any shopping trip.

That's great! Vector analysis with analogy - cool!
I'm glad I had the opportunity of a McGizmo in hand from the passaround or I'd have to ask what the Kilroy is but I'm sure I got that one figured as I did look inside. It all made sense to me in reading this exactly what is happening. I wonder if a very thin nylon sleeve would help this?