Gas spring lift strut recharge DIY - truck cap.
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- čas přidán 23. 08. 2024
- Lift struts are elegant and ingenious but so is the planned obsolescence from the manufacturer's view. Quickly rejuvenate them rather than throw them out.
-------------------------------------------Math Example-----------------------------------------------
If P1=400psi=2757902.8N/M^2 and Area A=38.48 10^-6 M^2 (7mm arm cross-section)
F=PA=106.124N
Weight=F/G=10.818kg or ~23.8lb. G=9.81M/S^2.
If the volume of the spring is conveniently cut in half when the arm is all the way in, then we have PV=constant so P1V1=P2V2 and
At V1 the spring supports 10.818kg. Sufficient for a light tailgate. It's that simple.
At V2 the spring supports 2 x 10.818kg.
Charging a spring with 7mm cross-section arm to 400psi will support 10.8kg. If the arm cross section increases to 10mm then 400psi supports (10/7)^2 times as much.
You my friend are a genius. These struts are getting waaaay too expensive
Thanks - great vid, right to the point with a clear quick explanation of the math/principle behind. much appreciated.
And in the end you save $20.00 minus your time and effort. I am lazy and will order off Amazon, but still an interesting video from a guy that's a whole lot smarter than me.
My john deere damper is one of a kind and is $120 for an aftermarket. If this fixes my problem, I'll do a backflip.
@@mightymightymightyman199 how’d it go?
@@bruhh8908 Haven't fixed it yet. Still working on my cub cadet tank48 zero turn's hydros.
This is a true repair video. Thank you
wow! that's not easy!! I will buy a replacement. thx for share your experience.
Thanks mate, it works! it was a bit hard to solder the brass tube against the steel tube but worked at the end. I wish there was a self threading valve!
Right on.Thanks for the thanks! Fight the power :)
Soldering is a skill one gets fast & good at.
Clean metal, patience, sufficient torch heat directed near but not directly at the site, flux core solder, and ideally leaded solder (lower melt temperature and works best).
Self-threading valve: Indeed, that would be handy. If such existed I think would still want to solder it, rather than rely on thread glue for seal. Solder that grabs, flows shiny and then freezes assures an air tight seal and gives extra assurance the threaded valve won't fly out - the tube wall is thin and the pressure is high.
The best i've seen so far! Thanks so much.
Wonderful video but I ordered a pair of oem Hondas for 30 bucks. So I would love to be as handy as you, but I’m just as handy installing new ones and that’s about it. Lol.
I like your thinking!
This is a good fix if there is nothing wrong with the seal. Putting air in adds oxygen which means it will eventually rust internally. If you are serious you need to use Oxy free nitro . If you aren't looking long term air will do.
If the fail was a fade rather than catastrophic, you know the seal is good enough. So long as the inner walls are oily it will outlast the truck, which is why I added oil in the rebuild.
You are right that oxygen is a rust factor but moisture must also be present. Doing the recharge on a low humidity day would help, but in practice I won't worry. Convenient access to free nitrogen ends all debate. Nitrogen's primary home is in repeated quick compression systems like a car shocks, racing tires or my dirt bike mono-shock, to avoid heat buildup. The deep question is how long does something have to last? It depends on how old we are :)
It went down to minus 19Celsius a few weeks ago and my springs still lifted as intended. Gratifying.
I know this is 3 years old but, is the seal not exposed to the elements on the outside of the cylinder? How much more damage would the oxygen do on the inside if it is already exposed?
How do they go bad ?, if it has a broken seal, won't it not hold any pressure?
No seal is perfect and the oil eventually finds its way out with the help of pressure and each time the spring is cycled. The worst is when people make the mistake of installing them upside down.
I expect hydraulic seals in construction equipment die faster due to dust, dirt, wet, and scratches. Seals don't break, but they do wear, causing graceful degradation.
good job
I think I will buy and use valve extenders, that way I can tap and screw in plus jb weld
Air compressor tank fill valves I have ordered
It's worth a try. Bear in mind the force pushing the D=7mm diameter valve stem out is 400psi x [ 0.25 pi D*D / 25.4mm*25.4mm] = ~24lbs. Wear eye protection :)
You want a snug threading job and the open question is how good the JBWeld epoxy bond to the outside of the metal tube is. With no extra effort you could add a few wraps of wire around the tube on either side of the valve to give something extra for the epoxy to grab. It does not have to look good, it just has to be good.
@@htpac yes it’s a lot of force… worth a try though.
very nice and quite interesting. the air will react to heat / cold more than the nitrogen. this will cause leaks and may effect the accuracy of its function. or it may not. who knows. still very interesting.
" the air will react to heat / cold more than the nitrogen ". how much? given that air is, you know, like 80% nitrogen.
@@cgoody3170 I make this assumption based on race car tire inflation when we use air the tire pressure increases as the tire heats up and the air expands. when we inflate the tire with nitrogen the heat from the tires does not affect the pressure in the tires resulting in a more consistent tire through out the race. I would assume the same would apply with struts. I could be wrong I been wrong plenty of times in my life so being wrong is no stranger to me. lol what are your thoughts?
Yep, you are wrong , NASCAR your talking extreme conditions to cause slight differences. A gas trunk spring filled with air or nitrogen in any weather condition would have negligible to nil difference.
@@madeleyinc then why would the manufacturer use nitrogen and NOT simply air? it would be much cheaper to pump air in them than to buy nitrogen. according to the strut manufacturers that I spoke to when doing the research for this video it was used for the very reason I stated. a car heating up in the hot sun can get pretty hot and that will increase the pressure more in an air filled strut verses a nitrogen filled strut. higher pressure means more likely to leak and lose pressure. of course this is all based off what my sources explained to me. it makes no real difference to me either way other than to provide accurate information obtained from the people who build and design these units.
@@daveknowshow The manufacturer use nitrogen is just for the safety reason. Compressed air(with Oxygen)+ oil = might explosion .
You can use the google to translate the article. kknews.cc/news/xnn55no.html
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Seems like a hell of a lot of work. Struts are pretty cheap.
Thanks for the video. Would you share what you used to get 350 psi? This is pretty high pressure with DIY compressor. Thanks.
Google "bicycle shock pump" or "bike shock pump". They are cheap and plentiful.
There ain’t no way you can get upto 350psi with a hand bike pump thats about 20 bars lol our high end Compressor at home only goes upto about 280psi
@@teammouse why not. its take time but its possible. Psi, bar, kpa is pressure of air. Its doesn't represent volume of air or whatever
@@ayn30 you know with a hand pump the higher the pressure gets the harder it gets to push the piston down at 20 bars it will be nearly impossible to compress even more
@@teammouse Hmm i think you dont understand how hydraulic and pneumatic work.
do you have a little mistake , the area of the piston in order to calculate de spring force, should be the external diameter of the cylinder wich is the body diameter painted in black, less the thickness of the wall multiplied by two, so the force will be higher than you cvalculated before
The calculation is correct since the "piston" in these is just for damping as in a similarly constructed . And to act as a end stop, that is what the o-ring is for, not sealing. Pressure is the same on both sides which gives the effective area of just the area of the rod.
Nice video but be careful with 400psi air which contains 20% oxygen.
perfect
What are the reasons to stop working of the struts
No seal is perfect, and no machining is perfect. You may lose a little gas with every cycle of operation, but I suspect failure becomes quick when the small squirt of oil inside from the factory finally is used up. That is a good reason to remember to ALWAYS install these with the cylinder up and the stem down so the oil seal can stay oiled inside.
Shucks no room on mine for the valve. Wonder how they fill them at the factory?
Mystery machine #1
czcams.com/video/vRvJuHEm6UI/video.html
Mystery machine #2 (better view)
czcams.com/video/uuDO1ScCx2s/video.html
I once imagined liquid nitrogen would be directly involved but the invisible hand of capitalism solved that. Holding a new small gas spring in my hand and looking down the top where the arm enters, and referring to machine #2 vid, there seems to be an integral valve just by virtue of the construction which is then especially sealed by the internal oil when you invert the spring to its default orientation.
The tank PSI can be huge and a regulator can step it down to what is called for.
This is awesome... skills
Fantastic video...really interesting and I would love to try and see if I can do it. My strut is leaking some oil and I wonder if I have bad seals and a recharge would be ineffective. Do you have thoughts?
Thanks.
If you can see and feel leaking oil then bad seals for sure, and I would not expect to salvage it. That would be a good strut to practice the fix on if you would value the practice. If it was the usual slow leak and you no longer get the lift you need, then your strut is worthless but a candidate for the fix.
@@htpac Great information, thank you. I'll try that when I can get a valve...
How to fix if it is leaking ?
Nice idea, but there's a reason why they failed. With age, the seals dry out and allow the nitrogen to leak out. They're just going to fail again.
Everything dies, that's true. I bought the cap well used 15 years ago so the gas springs may be 30 years old in 2022. I have had to spend a few minutes charging them once since I posted the video but they still work.
The truck itself and the deer it hit are no more, but the cap lives on as a bicycle shed.
Would it be next level if I attached the valve with the strut still attached to the vehicle? :)
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The Saudi moving vehicle tire change trick needs a new twist - and you've hit on it
How did u disassemble the strut? Please can you add a video for that
The ends are plastic and just unscrew, as shown.
Maybe your strut needs a pair of small vice grips to start it turning.
I think I gently held the plastic captive in a vice and gripped the strut by hand to rotate it.
I have 2 small, stainless steel bodied Struts that hold my hood up. There aren't any holes going into the strut. How did they charge them up from the factory? How can I release some pressure?
Confusing me there.. i have 2 gas springs off a treadmill, both are half the size girth wise but same length. Now from factory they are charged to hold 165 lbs of weight.. takes a lot to compress em. So hows that cross sectional thing work again?
To a good approximation, PV=constant, so as you reduce the volume in your treadmill gas spring, the pressure goes up accordingly. Obviously if the housing volume is huge relative to the arm, then the pressure change between arm position extremes will be small. If the housing volume is small relative to the arm then you can get a much stiffer spring since the pressure change will be larger.
The force on the sliding arm is proportional to the cross sectional area of it, since inside your spring, forces on the sides of the arm balance out, and only force on the end is not.
Are the two, together, supporting 165lbs, or are each intended to handle that much independently? 165lbs is not far off the weight of a minivan hatch and I expect you need higher pressure than a 400 psi bike shock pump can supply. If your springs are junk you always experiment or just cut one apart for interest and see what it looks like inside.
Yea theyre junked off of 2 different treadmills. So one each is only used on the things is to assist when folding up the tread parts. But these things are ridiculously strong with the piston arm only a cm around and the strut assembly is about 1/2”. But extended they are about 2.5’ long tip to tip and half is piston rod and half is the housing. I really want to drill ahole and tap it with a schrader but i tell ya everytime i go to crank down on the press my giblets just start fighting and wont let me do it.. ive seen many drilled open with just a little psst like a coke can but my luck ill level my garage..
Theyre labeled 550n and other says 165lb. I weigh i know 210 and when i put all my weight on one or the other it just goes down so slowly. Maybe im not putting all my body in a linear motion and all but jeez..
You said minivan springs are around that weight though? I was wanting to decrease the pressure to add as hood or tailgate assists but figure the pressures are way too much as they sit. And worried about buckling at the little shaft like when your wife sits on it wrong real hard and ya make that sound.. ya know? Lol Gguhoooohshit! Ha! That’s funny right there..
@@Z-Ack You make me grin and also motivated me to add some example calculations in the video description. Your spring arms are 10mm diameter and from your description, the pressure is way up there - maybe 900psi. You have to have caution & respect and be thinking when dealing with that kind of pressure or hurt yourself.
Assuming I had such a high pressure source, I would want to do an excellent job brazing or welding the valve because if it let go it could travel like an air rifle shot.
Why couldnt you just make a air chamber from a threded pipe put strut in and pressurise chamber
That's a fucking great idea m8... Drill it through, tap it, screw in a screw-on valve or just drill, flux and solder and have the valve hidden inside the strut holding fist...
Would adding carbon dioxide prevent rust from forming as quickly along with reducing the speed of the leek as it is larger than nitrogen?
Technically yes, since there would be no reactive oxygen. Interestingly, An apple farm near me keeps apples in cold storage for up to a year in CO2 filled rooms. I buy from them year round.
Molecule size certainly illustrates itself in a helium filled rubber balloon so a bigger gas molecule has to be better, qualified by the size of the hole, which we don't know.
Your good idea is definitely an improvement and here is how I would cheaply do it: fill a garbage bag with CO2 from a tank (fire extinguisher supplier 99%, or beer making 99.9%) and then charge the spring as I have done, but inside the bag. CO2 is heavier than air so no problem keeping it in the bag. Using car exhaust might be nasty but I'll never admit I think it would work fine :)
I don't feel rust is primary or even secondary problem though. Internally the shaft is rubbed with oil every time the spring cycles, and the default resting position is compressed, protecting the internal shiny arm from the elements.
A deer wrote my truck off but I'm keeping the cap as a small woodshed so I can run the gas shock experiment indefinitely.
A better way to avoid needing to solder valve is to get a dry ice and throw it in the cylinder and reassemble it quickly. One drawback is getting the right pressure. Too much dry ice might cause the strut to rupture/leak, too less, lifting force won't be strong enougj
cheaper to just replace them and alot easier lol
It fails to fix the issue that caused the initial lots of pressure to begin with. The new air will just leak out faster and faster. What a waste of time. Just buy a new one.
It is still working without another pump up. It took me less time to fix them than to drive to the store and back. I put in more oil than the minimal amount from the factory so maybe that was the main issue. Also, don't operate these upside down or they won't last long.
Maybe. Gas is going to always be leaking out at a certain rate. After years of existence, even a perfect strut will deflate. If this fix lasts a year between charges, it is worth it. The real question is, Why don't all struts come with valves?
You should at least try to hit the seals with acetone. It should cause the leak to stop.
Way too much work
How many times are you going to smack your mouth like damn that shut is so annoying
Why don’t you show us how you did it instead of all that pv=nrt crap? We don’t give a damn about the gas laws... we want to see you fix it so we can do it the same way! Jibber jabbering wasting video... just show us. That’s what video is for.
Such gratitude! But I understand you paid big $ for expert advice and you expect it to be professionally rendered.
Honestly I think this is the first video I’ve ever gave a thumbs down to.. The video would have been much more useful without the science and video actually showing the work being done and the working result ie the gas strut fixed.
Plumbing soldering skill is a prerequisite. There are videos dedicated to that. Watch and do. Experience will bring you to the difference between a good solder joint and a "cold" one, which is the crucial thing you need to know. Get a feel for that and it is easy.
Science: aspiring to be ignorant of a few basics is a blindfold for the mind. Don't trust me..."trust the science" :)
@@htpac So the point of the video was to show everyone how smart you are versus actually showing the work done in real time. Got it. I stand corrected. News flash smart guy anyone can post a video talking from a high level of understanding about a variety of subjects they are well versed in. For example I happen to be an network engineer. It wouldn't be hard for me to post a video that was intended to show how to redistribute EIGRP into OSPF Then go in depth from a high level of understanding about the protocols, never actually showing me configuring anything only then say Voila all done at the end! Yes it would make me look smart but wouldn't do much for helping the person watching the video actually accomplish the task at hand.
Schrader valves are so cool! Here's a video on how to install one onto a spray can to make it reusable. czcams.com/video/doLPFPeJ6JE/video.html