Question Suunto Transmitter Modification, Possible???

[Zef]

Has anyone else given any thought to modifying the cover of a Suunto transmitter by putting threaded inserts into the screw holes?

I dislike the idea of re-using the self tapping screws and the cover is apparently not designed for the screws to be repeatedly removed and replaced. In the past this was less of an issue as official battery kits that included replacement covers were available for purchase and DIY installation, but now the covers are only available to shops who want to charge labor to open, change the battery, and screw the new cover in place.

I have no idea if a threaded insert is made small enough for the holes....does anyone know? If they are made in a size that would fit, can anyone advise on the size and the size bolt that would need to be matched up? I have spare transmitter cover that came in an official battery kit that was purchased before the recall, where the transmitters were returned with covers with white "o" on them....we have 4 transmitters....I would be will to test this kind of modification out on one of them if the hardware is available.

It would be great if these can be modified to make them more user servicable than they currently are.

Any thoughts on this out there?

-Z

 

[Scared Silly]

I do not think is not enough sidewall for a threaded insert without going to a smaller screw. If there is an insert with a smaller screw, a washer would be needed so get enough surface area so to cover the original hole.

 

[Zef]

I do not think is not enough sidewall for a threaded insert without going to a smaller screw. If there is an insert with a smaller screw, a washer would be needed so get enough surface area so to cover the original hole.

The holes in the replaceable cover are 3mm in diameter. I believe the holes are smooth bored and the threads are cut by the sharp threads on the original screws when inserted the first time.

The wall thickness is rather thin at the top of the holes but gets thicker deeper down.

I have no experience with helicoils and such so have no idea how the sizing works, but was thinking perhaps an M3 helicoil screwed in to the hole with the diamond profile of the helicoil cutting its own threads into the walls of the hole, or tap the hole with the correct size tap for the helicoil. Then just get the correct size bolt/screw to thread into the helicoil.

The screws insert through holes in the base of the transmitter before they are threaded into the cover. The cover is sealed by an o-ring. If a washer is needed under the head of the screws/bolts that thread into the insert, I would think that would be inconsequential other than ensuring the heads of the screws do not pass through the holes in the transmitter base.

-Z

 

[happy-diver]

You know, the trick when re-screwing into plastics type formulations, is to follow the same path
So if the screw threads in easily it's found its place keep screwing if it's tight or stops back it out

So you are not retapping therefore removing unnecessarily extra material equals loss of lifespan

And then when the screw stops screwing you stop screwing so you don't displace more material

So if when you mess your hole up because you were using Schwartzys big arm as a torquometer

You grab some screws the next size up, and then next size up again until there is no more plastic

Whence thence you find these brass doovers to push in affixedly

 

[Zef]

You know, the trick when re-screwing into plastics type formulations, is to follow the same path
So if the screw threads in easily it's found its place keep screwing if it's tight or stops back it out

So you are not retapping therefore removing unnecessarily extra material equals loss of lifespan

And then when the screw stops screwing you stop screwing so you don't displace more material

So if when you mess your hole up because you were using Schwartzys big arm as a torquometer

You grab some screws the next size up, and then next size up again until there is no more plastic

View attachment 811365

Whence thence you find these brass doovers to push in affixedly

View attachment 811366

Yeah, that old rescrewing trick works ok for stuff that doesn't see 3000psi of air pressure, but the AI transmitter does so I want to avoid the occasion where the threads formed by the initial insertion of the screws are not compromised...as failure could occur while gearing up which could cause personal injury, or it could occur underwater where the transmitter floods and is kaput.

I thought about the type of inserts in your pictures, but I am not sure they come small enough for a hole with a 3mm diameter....if so they would be perfect....I don't want to enlarge the holes as that would compromise the relatively thin walls around the holes.

The idea is to thread in an insert in place of the original screws that hold the transmitter shut, so that there isnt reptetive screwing/unscrewing in and out of the plastic for battery changes or for pulling the battery for storage.

-Z

 

[Scared Silly]

Yeah, that old rescrewing trick works ok for stuff that doesn't see 3000psi of air pressure, but the AI transmitter does so I want to avoid the occasion where the threads formed by the initial insertion of the screws are not compromised...as failure could occur while gearing up which could cause personal injury, or it could occur underwater where the transmitter floods and is kaput.

While the transducer sees 3000 psi the case does not. The case might see at best 100 psi. If the case floods the electronics are going to go kaput. The chances of the transducer having a sudden spontaneous discombobulation are slim. Further, there will not be much air loss from a HP outlet which will leak out through OPV in the transmitter.

 

[Zef]

I was under the, perhaps mistaken, impression that the whole transmitter filled with HP air. How does the pressure, apart from the transducer, reduce to 100psi?

-Z

 

[lairdb]

I was under the, perhaps mistaken, impression that the whole transmitter filled with HP air. How does the pressure, apart from the transducer, reduce to 100psi?

-Z

It doesn’t; that plastic case isn’t a hundredth the strength required to withstand HP pressures. The case (if properly sealed) maintains 1 ATM, and is subject to dive pressures on the exterior from the water column (e.g. Δ4 ATM or Δ59 psi at 133 fsw; Δ14 ATM or Δ206 psi at its max rated depth of 492 fsw.)

The HP air is contained entirely within the machined steel fitting where the pressure transducer lives.

In static o-ring applications, the pressure squishes the o-ring into the groove, sealing the opening; part-to-part fit is (within limits) mostly about retaining and positioning the o-ring. In other words, the screws are not resisting any pressure; they are effectively just retaining the cover vs. mechanical trauma.

The sort of inserts @happy-diver mentioned are probably too big for the amount of marginal plastic available, but helical coil inserts could probably be used; the drill size recommended for Heli-Coil M3 is only M3.2.

That said, you may not need it. Again, the screw is not resisting any meaningful pressure; as long as you never gorilla the screws, they may be fine for many cycles.

 

[lairdb]

[…] reptetive screwing/unscrewing in and out of the plastic for battery changes or for pulling the battery for storage.

“For storage”? I do not see that recommended anywhere, and I presume the battery is lithium based, which pretty much eliminates battery leakage as a concern. ”200 dives or 2 years”, otherwise stop fiddling with it.

 

[Zef]

“For storage”? I do not see that recommended anywhere, and I presume the battery is lithium based, which pretty much eliminates battery leakage as a concern. ”200 dives or 2 years”, otherwise stop fiddling with it.

Huh, thats 2 things I learned today:

1. only the transducer sees the HP air when the tank valve is opened, instead of the entire transmitter housing.

2. Lithium batteries don't have a tendency to leak like alkaline and batteries made up of other compounds.

I wonder how many other folks out there are operating under similar assumptions that I was?

-Z