Pannier Latch Failure - Not Only The Lid Has This Issue

[Brillot2000]

Hey All,

I just experienced an issue with the Pannier Latch on only one side on NaTalie yesterday evening. The right lid has been very stubborn to close after opening it. I removed the seat and started with the spraying the mechanism with silicone spray lubricant. There weren't any changes to the issue. I then inspected the catches on the lid and they were fine. Further poking around under the seat and then I noticed a loose screw near the latch assembly front. Further inspection showed that the screw came from the latch assembly and the other screw boss on the saddlebag backing was broken off. That explains why the front latch could not engage and what was creating my issue. The rear latch was perfectly fine.

What to do in a situation like this? I need the bike for the rest of the week. For a temporary fix, I decided to remove the linkage rod between the rear and front latch. This remedy eliminated the hard closing issue and will get me through the week until I can disassemble the bike to attempt a remove to the back saddlebag housing. Unfortunately to gain access to the area where the latch attaches to the housing requires almost completely disassembling the backend of the motorcycle. I will attempt this later on in the week leading into the weekend.

This issue was probably caused by the former owners years of abuse. I wanted to let everyone know those screw bosses on the lid are not the only place that can fail. Also if they fail on the saddlebag housings, there is a significant more amount of work involved before you can attempt a repair to this area.

Wish me luck with attempting the repair to this area.

 

[Sojourner]

I bought my NT new-old-stock and it still has only 2900 miles on it. After flawless performance, this summer the left side pannier wouldn't open. (funny, as I was showing the bike off to a guy at work.....)

First note to all: Be VERY careful on how much you tighten ANY of those screws that go into plastic. I stripped two of them; one lid latch/hook, one on the latch mechanism itself (the one Bruce is talking about). And I've worked in automotive plastic trim for years and know damn well how soft this stuff is! And I still stripped them out! With hardly any torque! (I seriously didn't put much torque on the screwdriver.....)

Removing and reinstalling both panniers was actually not that bad of a job. It was 2-3 hours of slow tinkering in the garage, and requires very few tools. 10mm and I think 13mm socket and extension, JIS phillips.... Just beware that when you remove both side cases, the fender/taillight/license plate bit will just dangle from its electrical cord. I took everything apart, took both latch mechanisms out, cleaned off all the grease, and lubed with a lighter-weight lithium spray, the same WD-40 brand that I use on garage doors or car doors.

In my case, the issue is hand-latch part of the mechanism. I'm getting some binding from the part where the little finger-lever works the release. I think my situation is unique compared to what I've seen here.

I wish I'd taken pictures, because I normally like making how-to's, but my hands were greasy and I didn't want to grease up my cell phone.

If you dig into it, Bruce, note that there are 4 screws that hold the latch mechanism to the side case housing. Note that 2 of these screw bosses serve as 'locators' -- they poke just ever so slightly through the metal latch bracket. One is a hole, one is slightly slotted, if I remember correctly -- a 4-way and a 2-way locator. Those provide the alignment of the latch mechanism, and should be tightened first, before the other 2 screws. It's difficult to see down in that dark plastic crevice.

I've got an idea in the works for how to make some hidden releases, where I can stick my finger in the little air holes forward of the panniers and push a little linkage to open my bags, if I have a problem out on the road. I don't want to get stuck with a situation like I had at work, where I couldn't open my left pannier, and therefore couldn't remove the seat.

 

[junglejim]

Yep, mine were broken there too. I removed the entire latch assembly (and the seat latch) and gave them to someone here on the forum. Then I added the external lockable latches from Southco. My NT was then 13 oz lighter.

 

[Brillot2000]

Removing and reinstalling both panniers was actually not that bad of a job. It was 2-3 hours of slow tinkering in the garage and requires very few tools. 10mm and I think 13mm socket and extension, JIS Phillips... Just beware that when you remove both side cases, the fender/taillight/license plate bit will just dangle from its electrical cord. I took everything apart, took both latch mechanisms out, cleaned off all the grease, and lubed with a lighter-weight lithium spray, the same WD-24 brand that I use on garage doors or car doors.

Thanks for the information. I had half the backend apart a couple of times before, that included the installation of the top box on the last go-around. I need to take it down even further this time, at least for the right. I will inspect the leftside in greater detail at that time.

 

[Sojourner]

Edited my post so no one looks for WD-24! (?)

I also added a SW-Motech Alu-rack, so that will have to come off now if I ever need to take the grab handles off again, to get to things like side cases.

 

[coaster]

The only lasting solution is to mount external latches, the flimsy plastic post arrangement will almost certainly fail given enough time.

 

[Sojourner]

All things will fail given enough time.

 

[Brillot2000]

All things will fail given enough time.

Being that I am an engineer. I can tell you that this was designed to fail. Also, that the design engineer thought it was adequate at the time.

 

[RedLdr1]

Also, that the design engineer thought it was adequate at the time.

Or much more importantly the marketing and finance dweebs thought it was adequate....:rolleyes1:

 

[junglejim]

Being that I am an engineer. I can tell you that this was designed to fail. Also, that the design engineer thought it was adequate at the time.

I think engineering has changed over the years. Many products are "designed" by the marketing department to sell to a particular market they have identified for a certain price which will be an advantage over any competition. Then the legal department makes adjustments to keep the company from getting sued. THEN the engineers have to figure out how to make the item for the price specified by the marketing department. OK, so this is a bit overstated, but the concept is certainly in use in today's commerce. The engineer no longer is charged with making the best product or the best functioning product or the longest lasting product. Manufacturers are in business to make money, not the best products.

 

[Warren]

I have been in marketing for 40 years. I have never told engineering how to design a product. We communicate features and benefit that customers are looking for and then a price point they are willing to pay. Engineering decides how best to accomplish that. Our legal department is also never involved in product designs. They do review all marketing and instruction documents to make sure we do not make unsubstantiated claims and that the appropriate safety warnings are provided in the manuals.

 

[Brillot2000]

I think engineering has changed over the years. Many products are "designed" by the marketing department to sell to a particular market they have identified for a certain price which will be an advantage over any competition. Then the legal department makes adjustments to keep the company from getting sued. THEN the engineers have to figure out how to make the item for the price specified by the marketing department. OK, so this is a bit overstated, but the concept is certainly in use in today's commerce. The engineer no longer is charged with making the best product or the best functioning product or the longest lasting product. Manufacturers are in business to make money, not the best products.

I a Nutshell, it is like that to a degree these days. It depends on the sector you are in though. We cannot forget about "Planned Obsolescence" as well.

 

[Sojourner]

Actually, I'm an engineer as well -- automotive design engineer for a good while, and a more general project/product (with CAD) engineer currently. The latch mechanism is complicated; key lock, release to 2 bags, 2 finger levers.... And to get it to latch and unlatch smoothly, and to latch it tightly and water-proof when closed.....it's a tall order. I think it's lacking in robustness, but it's not that the design team was negligent. Any little bit of manufacturing variation in that latch mechanism could make a difference between working and not. I really think they gave it a solid go and gave it their best shot. The only way it could have been better is for them to either have spent more time benchmarking other designs and previous designs, or having someone with a lot of latch mechanism experience on the team.

Having been in automotive engineering for many years, you would be amazed at how often the wheel is reinvented. There's a lot of talk of 'lessons-learned', but very little follow-through on it. I was frustrated with my previous company; it seemed like every time we designed a door panel, it was like it was almost the first time we'd ever designed a door panel. This is automotive. Now take that to motorcycles where the demands are less stringent (i.e. there isn't J.D. Powers surveys to satisfy!)

When I was at Fisker Automotive in Irvine, I was responsible for the door trim on the Fisker Karma. They were using a Corvette electronic door latch mechanism. I was responsible for making a cable-operated emergency release lever. Being safety-related, it made me nervous as heck. If you drive your Fisker into the water and the power goes out, you now don't have a way to electronically release the door. Hence the backup lever. I can feel for folks that design these things. There's only so much testing that you can do, and then it has to go into production, and you hope it works.

 

[mikesim]

The main problem is that the plastic bosses that the self-tapping screws are in eventually weaken due to the stress of the self tapping screw and crack apart. If only they would have molded in metal bosses that were threaded and used conventional screws, this problem would have never occurred. This sadly is experience from hindsight. In engineering an old maxim is that you learn very little from your successes, but a great deal from your failures.

Mike

 

[Sojourner]

Putting screws into plastic bosses is actually such a common practice that there are specially-designed screws for it, and plenty of good design standards. You'll find plastic screw bosses in cars all vehicles, be it Kia or Bentley.

Threaded metal bosses in plastic parts is referred to as 'insert molding'; the threaded inserts (often brass) are put into the injection molding tool, and then the plastic part is molded around it. It's used for things like grab handles, which are subjected to a high load. But it's rare because it's expensive. Screwing into plastic is extremely common, from the plastics in your Lexus to your kid's Mattel toys to the laptop I'm typing on.

The plastic bosses in the panniers could have been more robust, but for the sake of not going too far off-topic, I'll refrain.

 

[DirtFlier]

Making the plastic towers about twice as thick would have solved a lot of ills and the cost increase would have been nil.

 

[Sojourner]

Yep. Normally the concern with making thick screw bosses is that they cause 'sink' on the visible surface, which we call the A-surface. When the plastic is molded and then cools, it shrinks, leaving a visible dimple defect in the surface. This often limits how robust the boss can be; the thickness of the boss can only be about 50% of the thickness of the wall it's on. However, on the pannier lids for example, the screw bosses are not on the A-surface, they're made on a pocket (which we call a 'doghouse'), which is exactly what they should have done. With this, the can make the bosses as beefy as they want (80-90% of wallstock), but for some reason they didn't. So I chalk it up to inexperience of the designers; they just plunked the 'standard' boss in their CAD model and figured they were done.

 

[DirtFlier]

I think the base of the tower can remain as-is but they should have done away with the taper and just made it straight up-and-down. The tower being thicker at the top would have alleviated a lot (not all) of the cracking at the top.

 

[Sojourner]

Y'all are learning way more about plastic part design than you had intended.

I don't exactly recall seeing the taper when I did my pannier work, but there is a certain amount of taper that is needed for the injection-molding process, so that the part releases and can be ejected from the tool.

One other lessons-learned is that if you put a very small counterbore on the inside diameter of the screw boss, it helps prevent a crack from initiating from the screw cutting threads into the plastic.

Anyone here want to start up our own motorcycle company? I'll be the engineer of the plastic bits.

 

[coaster]

Or much more importantly the marketing and finance dweebs thought it was adequate....:rolleyes1:

This is the reason the flimsy arrangement is what have to deal with now.