Fundamental Flaws in the Palm Pre Slider

[Brain_ReCall]

I've been analyzing the pictures of the Palm Pre tear-downs (see iFixit and Rapid Repair) and I wanted to give you my opinion of the design problems in the slider. Please note that I do not have formal cell-phone design experience, so what I say may require a dose of salt.

First off, a quick refresher of terminology. In the below picture, the green sections are the rails, which are attached to the lower keyboard section. The red sections are the two shoes, which are attached to the upper screen section, and ride up the rails when the phone is slid open.




The primary problem with the slider is actually the mirror. Palm wanted a clean, solid mirror on the back of the upper section which means neither the shoes nor the rails could interfere with the mirror. Since the keyboard on the front on the lower section couldn't have any of the slider mechanism interfering with it, this left very little of the phone where the two sections overlap. In fact, its nearly split evenly, 1/3 to the keyboard, 1/3 overlapping, and 1/3 to the mirror. Since the phone expands by nearly the same amount when slid open, that means any slider would have to move over the entire length of the overlapping section. This forced Palm to go with only two points of contact per side: a single shoe, and a plastic guide underneath to provide torque to clamp the rail into the shoe.

The next problem is the shoes themselves. They are not even to each other. The one on the left is longer than the right shoe. The right shoe is positioned higher on the rail and the right rail itself is also shorter. This uneven design creates an inherent point of rotation since the two rails have different points of contact.

The third problem is a bit of speculation since I don't have a Palm Pre to rip apart, but I bet they are using a mild steel for the slider mechanism. This design requires a stiff material to maintain position. A mild steel could bend easily (even if slightly), which would exacerbate the existing problems to create a more loose slider.


The way I see it, Palm has three options to seriously fix the slider:

1. Redesign the slider. Ignore the requirement to have a perfect mirror. Instead, swap the parts around. Put the rails on the upper screen section, and the shoes on the lower keyboard section. Extend the rails all the way up to the top of the mirror. Then, this would give you enough room on the sliders to have four shoes on the lower keyboard section. Make sure all four shoes are even, identical, and positioned at the four corners of the overlapping section. This is the best option, but obviously the most expensive and invasive.
2. Redesign the slider. Redesign the lower keyboard section in whatever way possible to create two equal length rails. Then, make both of the shoes identical and even to each other. This solution does not fix the primary problem, but may be enough to eliminate most of the oreo-twist that we would see. This works best when solution 3 is also implemented.
3. Use stiffer steel in the slider mechanism. This would help reduce the long-term loosening of the slider, but only works best when also employed with solution 2.

Please let me know what you think, but please keep it on topic to the design of the Pre's slider. Posting anecdotal evidence that you have/don't have issues with the slider does not help the discussion.

[scoobdude]

Screws instead of rivets would help alot as well. But besides that 2 of my bad sliders were do to the plasic being at off curveture (spelling) to each other. Meaning one piece was not going with the same size circle if that helps explain it.

Also if that is your phone, hid your hex.

[Brain_ReCall]

Originally Posted by scoobdude

Screws instead of rivets would help alot as well. But besides that 2 of my bad sliders were do to the plasic being at off curveture (spelling) to each other. Meaning one piece was not going with the same size circle if that helps explain it.

Also if that is your phone, hid your hex.

Screws to attach the shoes might help. Screws would be weaker than the rivets, but can be tightened if loose. Your change in curvature is probably result of the steel slightly bending.

No, its not my phone. Its a GIMP'ed pic from Rapid Repair.

[80sCartoon]

If you want to look at a strong slider look at HTC and Samsung sliders. When you slide them open, you notice that the top half is actually what holds the rails, and the shoes are in the keypad half of the phone. That allows the shoes to be at the upper half of the phone, which makes for a stronger hold when you slide the phone up, especially since you're sliding the rails themselves not the objects sliding on them.

Also with that design it doesn't matter that the shoes are so much lined up, it's that they're longer. The Pre's shoes are simply too short (I blame the ancient art of Chinese foot binding), so it's not so much that they're not perfectly symmetrical but that their short stature allows one to slide up the railing further (literal twisting).

The solution is simple,find a way to make the shoes a little longer. In a perfect world they would redesign the rails on the screen half like everyone else had done it but oh well. I mean this phone had a LOT of design innovations unique to this phone, and this is most certainly a noodle-scratching design from Palm's past ones. Just like the Blackberry Storm this was a test run, who knows how a second Pre will look and feel (not the EOS, mind you.)

[StoneRyno]

I had similar observations. But this slider setup not only allows for the twisting that we observe in varied degrees depending on if the mechanism is damaged or not as tightly pieced together as it could have been but it also allows for the two halves of the pre screen halfand keyboard half to pull apart from each other since the only point of connection between the two is approximately in the middle where those shoes sit on the rail in the close position. This also lends to making the slider worse since it too can bend the slider parts. Dropping the pre can cause the most stress on it and is one of the most likely scenarios to be the cause of the most damage to this slider. The 4 point contact type would more or less eliminate the twisting even after being dropped a number of times or at least spread the wear out over much longer period of time.

When I got mine on launch day it was pretty tight with only maybe 2mm of twist and the screen and keyboard halves were aligned flush. After dropping it twice (different occasions) the screen half overlaps the keyboard half at the keyboard end by about 1mm and the twist is about 4mm. I don't slide it open and closed a lot so right now it doesn't seem to have contributed to it but in time it most likely will and possibly before I'd be looking to upgrade to the next generation of webOS device.

[Bishounen]

Good Lord I hope it wasn't just to have a shiny back that Palm made that poor design decision.

The silly thing is that if they had mounted the rails on the screen side and 4 shoes (or two larger ones) on the bottom side they could have still had a nice shiny back. just simply have the outside (non-contact) of the rails mold to the outside edge of the slider. it would have looked just as nice and been significantly stronger.

Thankfully my pre hasn't developed any significant twist to it. It "jiggles" maybe .05 to 1 degree. So almost no looseness, even after being dropped onto a concrete floor and getting a small internal crack in the side. (it's in the screen material, but on the side of the Pre, so not noticeable.)

Of course, I totally baby this thing, and am getting the rubberized shell and screen protector from the Pre central store as soon as I can. Still, I do worry about the longevity of it. I suspect I'll be using that Asurion warranty. Hopefully I can nurse the Gen 1 Pre through until the Gen 2 models replace them.

Ah well, that's the price of being cutting-edge I suppose.

[fritzk3]

Here's a new one... so as of last night, my slider has somehow found a new hard-stop which prevents it from sliding to the completely open position - when the upper half hits this stop, the tops of the upper row keys of the keyboard are still covered such that I cannot read the symbols on them.

I've tried taking off the battery cover and removing the battery, to see if something had gotten lodged in the rails, but couldn't see or hear anything that would be causing the problem. I've also lightly hit the device with the palm of my hand on both sides to see if I could jar anything loose, or back into position. Nothing has helped.

Any ideas what could be going on here, or what I might be able to do about it? I bought the Pre on 8 Aug, and it's now 15 Oct. I don't have the TEP... any chance I can get this thing exchanged for free due to what appears to be a workmanship issue?