OP
SP MK5 rebuild ?
- Thread starter HenrikBP
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halocline
Contributor
Are you saying you have 2 MK5s that have different pistons from each other? That's not right, ASAIK there's only one MK5 piston type, at least for the later ones. If they're still apart, take a photo of each and post it. If what you are saying is true, there's a chance someone put the wrong piston in your reg and you might need to use a different type of seat. I don't get the "slim" shaft bit; those shafts must be exactly the same diameter and length or you'd never get the reg to work. Is it possible that one of these regs is a MK5 clone and not an actual MK5? Please post photos.
You can get both conical and flat filters from the trident catalog.
You can get both conical and flat filters from the trident catalog.
OP
HenrikBP
Contributor
Yes, I have two late model MK5s (5 LP ports and standard size HP and LP port threading), and the two pistons have a slightly different profile with one having a slightly thicker section at the base of the piston. I've tried to illustrate below:
On the piston to the left you can see how the piston stem has a thick base that stops well before the section of the stem that passes through the regulator body. The stem part of both pistons is identical in diameter, and overall length is the same as well.
Sorry, the thick piston base is in the reg I just assembled and I forgot to take pictures.
Btw. just to be clear, the 2 regs on the doubles is a MK10 on the right post and the MK5 on the left.
Henrik
R
redacted
Guest
I looked at a few of mine that I could get to and they all have the slight ridge. It does not appear that it serves any function other than they had to stop the machining of the sealing surface of the piston shaft somewhere. Unlike the Mk10 piston where the ridge is quite large, it is probably not enough extra metal to effect the cooling/freezing process. I'd bet some engineer simply realized an opportunity to reduce production costs by eliminating unnecessary machining.
I played a bit with the universal din retainer on the Mk5 but decided it is probably not a good idea. While it will seal and does appear to work if the saddle is modified or eliminated, I am not comfortable with where the tightening torque forces are being distributed. I suspect that all the applied torque is going into crushing the o-ring. With a correct retainer, I believe most of that torque is being absorbed by a designed bit of metal to metal contact which helps retains the torque spec.
BTW, unless you just have to have a new $135 tool, you can extend the range of your torque wrench by changing the length of the torque arm. I use a slide bar engaged by a socket that I cut grooves in to lenghten or shorten the torque arm. Should not be too hard to take that 40 in-lb setting down to the 30 to 35 in-lb range by shortening the torque arm. I used two torque wrenches to calibrate the setup as I was not real sure of the original torque arm length. But if your 1/4 inch drive torque wrench has a 10" torque are, you can use the slide bar to shorten that to about 8 inches which will give you 32 in-lb on the 40 in-lb setting. Then you can use that $135 to buy a couple more regulators. That grooved socket is also handy for engaging allen wrenches to torque those fittings when you don't have allen sockets.
I played a bit with the universal din retainer on the Mk5 but decided it is probably not a good idea. While it will seal and does appear to work if the saddle is modified or eliminated, I am not comfortable with where the tightening torque forces are being distributed. I suspect that all the applied torque is going into crushing the o-ring. With a correct retainer, I believe most of that torque is being absorbed by a designed bit of metal to metal contact which helps retains the torque spec.
BTW, unless you just have to have a new $135 tool, you can extend the range of your torque wrench by changing the length of the torque arm. I use a slide bar engaged by a socket that I cut grooves in to lenghten or shorten the torque arm. Should not be too hard to take that 40 in-lb setting down to the 30 to 35 in-lb range by shortening the torque arm. I used two torque wrenches to calibrate the setup as I was not real sure of the original torque arm length. But if your 1/4 inch drive torque wrench has a 10" torque are, you can use the slide bar to shorten that to about 8 inches which will give you 32 in-lb on the 40 in-lb setting. Then you can use that $135 to buy a couple more regulators. That grooved socket is also handy for engaging allen wrenches to torque those fittings when you don't have allen sockets.
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OP
HenrikBP
Contributor
Thanks awap. I gave the Universal DIN a few tries as well. But the shape of the shoulder that should hold the sealing o-ring as well as the threads in that area made it near impossible to get the o-ring to stay in place when I tried to screw in the retainer, which in turn made it unlikely that it would provide a reliable seal.
Torque wrench: Let me be upfront and admit that I'm a gadget freak and tool-a-holic, so any excuse to buy a new quality tool is hard to resist. That said, the torque arm is a great idea!
I would probably go for a torque arm length that would reduce the torque to half. That way the needed ~30 in.lbs. would be safely inside the rated range of the torque wrench. It should be possible to calculate how long the arm would have to be if I can determine the length of the "torque arm" of the wrench itself. I would guess it would be the distance from the center of the 1/4" bit to the base of the wrench handle. Well worth looking in to.
Spare $$ for regulators is a good thing no doubt, but I went through an eBay buying binge awhile back and should hold of for a bit
Henrik
Torque wrench: Let me be upfront and admit that I'm a gadget freak and tool-a-holic, so any excuse to buy a new quality tool is hard to resist. That said, the torque arm is a great idea!
I would probably go for a torque arm length that would reduce the torque to half. That way the needed ~30 in.lbs. would be safely inside the rated range of the torque wrench. It should be possible to calculate how long the arm would have to be if I can determine the length of the "torque arm" of the wrench itself. I would guess it would be the distance from the center of the 1/4" bit to the base of the wrench handle. Well worth looking in to.
Spare $$ for regulators is a good thing no doubt, but I went through an eBay buying binge awhile back and should hold of for a bit
Henrik
Since you guys keep bringing up the universal din retainer, would it work on a mk10 better than the mk 5? If so, has anyone got one they want to part with for a reasonable cost?
R
redacted
Guest
I believe the Universal DIN Retainer is good for all the more modern 1sts including the Mk10. But, if you have a Mk10 din conversion kit, the older style retainer that is part of that kit is fine.
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