HestiaPi Touch ONE rivet replacement


#1

I just received my Touch and upon opening the package the 4 plastic rivets were scattered in the case. I put them back in place but they simply fall out if I turn the wallplate over.
The documentation states that ‘4 x 2.5Mx25mm hex screws’ and corresponding nuts should be used. The closest I can find are specified as ‘M2.5-0.45 x 8 mm Phillips Pan Head Stainless Steel Machine Screw’. I think the pan head should fit in the hex recess and I don’t see why one would want 25mm screws to go from the wallplate through the PCB. Has anyone else actually found the recommended fasteners?


#2

Ah… those rivets… A lot of people won’t like them… We don’t blame them.
The first 3D prints had a nice tight fit but then the mass order had some issues with precision and the rivets like precision. The problem is that the ring part of the rivet that goes to the backplate needs to stay put but it too lose. If you can add a tiny drop of superglue between the backplate and the ring (leave the pin of the rivet out till its completely dry) while holding the ring 1-2mm off the backplate that would do the trick.
The metal screws and nuts are an alternative but we didn’t want to have metal parts inside for obvious reasons.
Let us know if the superglue did the trick for you. Pushing the pin through afterwards should keep the PCB in place with no problem.


#3

If you are in the US where metric sized screws might be a little harder to find in the stores, a #2 or 3/32" diameter screw with matching nut will work. The thread doesn’t really matter so long as the nut matches the bolt.

I went to three different stores before giving up myself and just stealing a set of screws and nuts from an RPi zero case I had around an old machine I’m not currently using.

I never thought of the superglue idea but after losing both the pin and the receiver for one rivet (I think it fell down a vent) I gave up.


#4

I’m going with the screws as only one of the four ring parts of the rivets actually ‘grabs’ the pin, the other three do not hold the pin at all even if I have them pushed into the appropriate position. I’ll look for nylon fasteners but don’t hold out much hope. Given that every computer motherboard in a PC is held down with metal fasteners I’m not certain why the comment about metal parts not being desirable makes sense…


#5

The plastic of the case is not strong enough to hold a threaded screw so a nut would be needed. If for some reason this gets loose where mains runs, it will be a problem. Also moving the PCB while powered with the metal staying on the back panel can sort pins. This is not the case in computer motherboards where materials are precisely designed and cut but I can totally see your point for someone who knows what to pay attention on. It was a hard decision and the lack of space (height) limits the options so keep that in mind if you go for an alternative. Having the nut at the front (hex headed screw locked at the back of the back panel) allows longer screws to be used and a greater range of possible dimensions. Overtighten the nut is not required and actually not desirable.


#6

I ended up ordering M2.5-0.45 8mm screws & bolts. Everything fit well. It would be nice in the future to consider making a thicker wallplat that could be threaded for machine screws. I’ll actually get the thermo installed this weekend.


#7

We are changing the design for manufacturing as 3D printing is not good for our future plans.
Adding extra thickness to the backplate adds to the total height off the wall of the thermostat which already feels a bit on the thick side. We are considering FR4 material (what PCBs are made of) which can be massively produced, is strong while not thick (2mm) and can come in some colours. Shipped flat and assembled with soldering the joints. Still a long way to go…