Gas struts suddenly failing

[m.tweedy]

The gas struts have supported the open lid very well until recently. They now cannot seem to take the weight and the roof closes virtually straight away. Cold? More importantly how do i resolve the issue.

Thank you.

[Peter Drew]

Most likely the cold. Try warming with a hairdryer and see if it makes any difference.

[Louis D]

You don't state how old they are.  Gas struts fail after about 10 years on car hoods (bonnets in the UK?) in my experience.  I never noticed cold having any effect.  I'm thinking your struts are undersized for the load and that you've gotten lucky up to now.  You could try get higher capacity struts, doubling up the existing struts, or adding a prop rod to hold it open, relegating the struts to an assistance functionality when opening.

[MARS1960]

Probably the cold temperatures, or they have lost gas over time.

[MARS1960]

2 minutes ago, Louis D said:

You don't state how old they are.  Gas struts fail after about 10 years on car hoods (bonnets in the UK?) in my experience.  I never noticed cold having any effect.  I'm thinking your struts are undersized for the load and that you've gotten lucky up to now.  You could try get higher capacity struts, doubling up the existing struts, or adding a prop rod to hold it open, relegating the struts to an assistance functionality when opening.

Undersized is a strong possibility hence losing gas before their time.

It could be the cold, the gas contracts and reduces output force in cold weather.

[m.tweedy]

Thank you all. The cold seems to be the likely candidate.

They are second hand car tailgate struts and could also be failing (£7.00 each is not a great cost to replace).

I did try a number of other ones in varying strengths before finding these held the roof open and closing it took a little pressure to pull it down. 

Thank you Peter I will try the hairdryer to see if that helps.

As it happens i have been using a clothes prop to keep it open as a temporary solution but do not like climbing around (have you seen my back).

[Davey-T]

The tailgate struts on my old Kangoo now barely support it, have to hold it  up when unloading to avoid banging my head, don't seem to be affected by cold though, just old age, bit like me 

Dave

[wookie1965]

I had to replace the struts on my 13 year old vectra after the boot lid crashed down on my head.

[RichM63]

Cold. The gas struts on the tailgate of my ML are fine in summer, but in winter I nearly always get 'brained' loading beer in the back.

[johnfosteruk]

5 minutes ago, RichM63 said:

Cold. The gas struts on the tailgate of my ML are fine in summer, but in winter I nearly always get 'brained' loading beer in the back.

As opposed to getting brained after you’ve unloaded the beer! ? 

[MARS1960]

5 minutes ago, johnfosteruk said:

As opposed to getting brained after you’ve unloaded the beer! ? 

Beat me to it .

[m.tweedy]

By jove i have got it.

Dew bands for gas struts-a new sideline..

[LightBucket]

You would be better off replacing with ones that are too powerful, and then releasing some of the gas till they are just right, there should be a release valve on them, this way they will last longer...

[m.tweedy]

6 minutes ago, LightBucket said:

You would be better off replacing with ones that are too powerful, and then releasing some of the gas till they are just right, there should be a release valve on them, this way they will last longer...

Been there and released too much. Woops. Hence the cheap second hand ones.

[Louis D]

2 hours ago, m.tweedy said:

have you seen my back

Is that your back (neck?) X-ray in your avatar?  Ouch!

[m.tweedy]

Just now, Louis D said:

Is that your back (neck?) X-ray in your avatar?  Ouch!

lower back ouch YES

 

[JOC]

In my experience with car boots it's going to be the cold.  The gas expands less when the strutt is cold.  The seals could also contract or crack in the cold letting some gas escape 

[Shibby]

The ones on my car boot expired when it was only 4 years old!

If you haven't already, I would add some sort of locking "mechanism" e.g. a safety wedge that you can pop in when open. The thought of it dropping down on your telescope is not a nice one!

[Sp@ce_d]

Ah mine failed on the tailgate last weekend in the cold. Unfortunately my wife was using my car in the dark. Opened the boot turned to grab shopping from trolley not noticing it was stuck halfway! End result a lot of blood from thankfully a small head wound.. gave me a fright when she got home looking like a scene from “Carrie” !!

[m.tweedy]

On 13/12/2017 at 10:10, Shibby said:

The ones on my car boot expired when it was only 4 years old!

If you haven't already, I would add some sort of locking "mechanism" e.g. a safety wedge that you can pop in when open. The thought of it dropping down on your telescope is not a nice one!

Thank you. A clothes prop makes a good safety wedge. Fortunately my scope does not protrude over the top

 

[Stargazer33]

A similar thing happens with car tyre pressure. The extreme cold causes the metal wheels to contract. This in turn pulls the rim away from the tyre and so lets out a bit of air (especially if you hit a pot hole). The air inside the tyre also cools and so takes up less volume. That's why it's important to check your tyre pressures especially during significant temperature changes.

[Charic]

I would just replace them. If you could source a more substantial gas strut, it could be more beneficial, maybe last longer, even through the colder snaps!
The cold can affect the oil (damping) and the Nitrogen (spring?)

[MarkyD]

Vauxhall Vivaro Tail Gate struts are pretty robust

[m.tweedy]

4 hours ago, MarkyD said:

Vauxhall Vivaro Tail Gate struts are pretty robust

They were actually from a Vauxhall vectra

[Jannis]

Isn't the gas in those just locked in by a rubber seal? I'm thinking that while cold itself will affect it significantly, it's also possible the rubber seal have been damaged?

I use linear actuators myself, so it can't be compared, but i do notice that every night i've been outside and it's been moist that they have been completely covered in ice after just a couple of hours.
When i'm closing the roof it's scraping of quite a bit of ice. For electric actuators this isn't a huge problem, but for a gas strut i wonder if this could lead to the rubber seal failing rather quickly?

If icing isn't an issue for you, then it's most likely just that they are worn out, or just not strong enough for use in the cold. Replacing them with a slightly a larger model is probably the best and easiest solution.

Alternatively you could do like me and use an actuator instead. Unlike a gas strut they will "lock" in any position (no risk of getting hit by the roof), and naturally requires no physical work to open and close. There's also no seals to really worry about being damaged by ice.
However, there are some downsides to it also.. It's maybe a bit more expensive, requires a battery + switches (or a remote), and if it should ever fail in an open position there it no way to close the roof without removing the unit.
My roof also got frozen stuck once by a madly thick and strong ice layer, causing one hinge to be ripped off and another to bend. This doesn't seem to be an issue with your design though, but if you do go for actuators, don't underestimate how strongly you might need to attach those hinges...