PBT spacebar warping with ambient temperature

[minho]

A bit of an odd problem that I wonder if anyone has found the solution to:

My 6.25u PBT spacebar shrinks with the cold (temperatures fluctuate between 60-75F in my apartment currently because I just roll with whatever temperature it is outside in the winter). This results in the two lateral stems being closer to each other, and the stems rub against the stabilizer, causing the spacebar to get stuck in the down position.

Any thoughts on how I can fix or prevent this? Has anyone tried "stretching" out a spacebar before? (ie heating it with a hairdryer and then pulling gently?)

I could get a new spacebar, but i really like this set and would rather keep it all uniform and cohesive. I know long PBT keycaps are a bit harder to manufacture because of these issues, and I'd rather stick with all PBT if possible.

Thanks!

[Leslieann]

If it's a temp and thermal shrinkage problem odds are not the plastic shrinking but the metal stab and the plate changing. Plastic dimensions remain pretty constant up until hit the TG temp which this is nowhere near, metal constantly changes. Right idea, just blaming the wrong component. The cap may still be warped though and it may be hardening at colder temps not allowing it to flex enough to compensate.

First of all, do NOT use a hair dryer. Plastic doesn't soften like metal because it doesn't conduct heat the same way. You need to bring up the heat in very small increments over a long period of time to avoid hot spots. People are just not good at this.

Check your spacebar stab for bind. I've seen them rub cases, rub the pcb, twisted, and just poorly made. Maybe swap the plastic bits with another one and see if that helps. It may just be a bad bit of plastic.

Is this a hot swap board? If so, remove all the switches, loosen the PCB and plate, allowing them to shift, now put the spacebar switch and cap, then the other stabilized switches and caps, then re-tighten and finish assembly. Tolerances on hot swap is far more critical than soldered as the switches are not free to shift before soldering. Will this fix it? maaaybe.

Another fix may be to simply install a stiffer spring in your spacebar to overcome the issue. Considering the size and weight of the spacebar and that it's handled by your thumbs you can often go up 5-10grams in spring weight and not even notice really.

Finally, there is no guarantee a different spacebar will be better, but you can buy just space bars and not whole cap sets so that may be worth a shot.

[typo]

Leslie is very correct about Hairdryer. It is not a regulated heat gun. You have no clue what you are applying. This most often goes pretty wrong pretty fast.

This is OT but it is warm and dry in here. My custom MX space bars have done fine. Stock New R2 Topre Bars have not done well at all. I just find it sad that Topre gave in to the pressure to supply PBT space bars and perhaps did not do the best job out of all companies. You would have thought they had this down.

You know space bars are long. This is precisely why many companies are hesitant. This is what often happens. I would say in the future keep it cool and RH up. I will guess that your room is just like mine. I mean I own the entire very large home but oddly hang out in one room. The entire place is much too warm. Our HVAC is so efficient I hardly care. Regardless high temp/low RH inside just destroys your entire home. Although I doubt it is 35 below zero by you and I do not mean the wind chill. Maybe keep them in a cheap cigar humidor if not in use. I am not kidding. I would gather most folks have more keycaps than keyboards.

[minho]

If it's a temp and thermal shrinkage problem odds are not the plastic shrinking but the metal stab and the plate changing. Plastic dimensions remain pretty constant up until hit the TG temp which this is nowhere near, metal constantly changes. Right idea, just blaming the wrong component. The cap may still be warped though and it may be hardening at colder temps not allowing it to flex enough to compensate.

First of all, do NOT use a hair dryer. Plastic doesn't soften like metal because it doesn't conduct heat the same way. You need to bring up the heat in very small increments over a long period of time to avoid hot spots. People are just not good at this.

Check your spacebar stab for bind. I've seen them rub cases, rub the pcb, twisted, and just poorly made. Maybe swap the plastic bits with another one and see if that helps. It may just be a bad bit of plastic.

Is this a hot swap board? If so, remove all the switches, loosen the PCB and plate, allowing them to shift, now put the spacebar switch and cap, then the other stabilized switches and caps, then re-tighten and finish assembly. Tolerances on hot swap is far more critical than soldered as the switches are not free to shift before soldering. Will this fix it? maaaybe.

Another fix may be to simply install a stiffer spring in your spacebar to overcome the issue. Considering the size and weight of the spacebar and that it's handled by your thumbs you can often go up 5-10grams in spring weight and not even notice really.

Finally, there is no guarantee a different spacebar will be better, but you can buy just space bars and not whole cap sets so that may be worth a shot.

Thanks for the detailed reply!

Using a Ducky Shine 3, which unfortunately is plate mounted and not hot swappable, so using a stiffer spring, or even just replacing/adjusting the stabilizers would require me to desolder all of the switches, remove the PCB from the plate/switches, and then perform whatever modifications I want to perform.

I think finding an alternate spacebar might be my best bet here... thanks for the warning against heating up my current one 

[Polymer]

On the flipside...

Many people have taken a hairdryer to their PBT spacebars with good success...and in fact, it is the only realistic way to do this for most people.

Given you don't seem to have other options...simply seeing if your spacebar is already a bit warped and might need to be twisted slightly is probably a worthwhile option vs looking for a completely new spacebar...

I'm a bit surprised a relatively small change in ambient temp is doing that to your spacebar though..

[Darthbaggins]

Thought I had heard of a hot water method to getting them as close to true as possible

[bkrownd]

I also have a warped PBT art spacebar.  I'm guessing that it would have to be put in a jig with 3 aligned mounting posts before applying heat to get the post holes to re-align.  It's the misalignment of the 3 post holes that causes the binding.  However, if temperature changes caused further regular misalignment then it's probably a lost cause. 

[Darthbaggins]

I would almost think, with said jig - almost use something like a stabilizer that could pull it to true (of course if the stabilizer is true as well). 

[Leslieann]

Many people have taken a hairdryer to their PBT spacebars with good success...and in fact, it is the only realistic way to do this for most people.

I'm a bit surprised a relatively small change in ambient temp is doing that to your spacebar though..

I'm surprised as well, it's likely the difference between rubbing and rubbing too much or grease thickening. On the other hand, that's a pretty decent temp swing on a product not really designed for it.

As for the hair dryer, how many people try that and fail, more specifically how many never reported that it failed.
This is a MAJOR issue on the internet. People read of someone else doing it well and they start blaming themselves or not want to look stupid. I've seen this an insane amount of times on 3d printing forums where absolute garbage engineering ideas gain traction because no one wants to counter the narrative. Same with Instagram and social media, people tend to only show the high points or the major failures for e-points to get the internet points.

[Leslieann]

Thanks for the detailed reply!
Using a Ducky Shine 3, which unfortunately is plate mounted and not hot swappable, so using a stiffer spring, or even just replacing/adjusting the stabilizers would require me to desolder all of the switches, remove the PCB from the plate/switches, and then perform whatever modifications I want to perform.
I think finding an alternate spacebar might be my best bet here... thanks for the warning against heating up my current one 

You're welcome.
Hard mounted actually means it's less likely to be an alignment problem between the switch and stab, I've really only see the issue on hot swap.
Desoldering one switch with braid isn't terrible,  it's when you have to do an entire board that it gets old real fast so if it does come to that, remember, it's only two (or 4) points to desolder. You could probably do it without any desoldering tools if you're careful, it's tricky but I've done it to various electronics, it;s not even that unusual as there is special solder for this purpose even. I would have a replacement switch handy though just in case you damage that.

[Riverman]

I also have a warped PBT art spacebar.  I'm guessing that it would have to be put in a jig with 3 aligned mounting posts before applying heat to get the post holes to re-align.  It's the misalignment of the 3 post holes that causes the binding.  However, if temperature changes caused further regular misalignment then it's probably a lost cause.

I think having a jig is more important than anyone lets on, but no one makes one that I've seen.  I've bought quite a few sets of PBT keycaps with slightly warped space bars, but they all worked.  The manufacturer's molds must keep the posts straight, and it's probably just the sides that shrink and warp while it's cooling.  The only space bar I've had that would bind on a couple of keyboards was one I straightened myself on my workbench with a heat gun, I'm sure because straightening the spacebar got the posts out of whack.  It worked fine before I messed with it.