Gas Strut Calculation

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Gas Strut Calculation

Postby TimC » Sat Jul 13, 2019 2:24 pm

Hi all, been a while. I've just been enjoying the teardrop and have decided to upgrade to gas props for the hatch. Did some research and have been looking over danlott's calculator. I'm hoping Dan or someone out there can look over my photos and data and educate me on how this all works. I want to end up with the much talked about gas struts that help me raise and lower and don't put too much strain on my living hinge.

First my hatch length which comes to 51". Hope I haven't overdone the photos, just want to be sure my method is correct...

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Entering that data into the calc it comes up with an ideal extended length of gas spring in inches of 30.6" And, number of springs left at "2". This is where I become confused. I'm thinking I then go to finding gas struts that will extend to this value (or close) and enter the actual I find. I don't understand why I am doing this before I find out the required force of the gas struts as that will further limit my sources for struts, correct? So, I go looking around and the struts are either about 27" or 36". Nothing found so far around 30"

Let me add photos and data I've measured and see if someone can help me get to the next step. Using the following method I come up with a hatch that weighs 54.3#. Round that down to about 54 or less due to the 2x2 and other blocks of wood adding weight to the final number.

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The next four photos show the hatch and galley areas that the strut will attach to. The first two photos show that the current and hopefully final hatch end attachment point is 24" from the hinge. I'm OK if that is not a viable point to attach the hatch end of the strut. It would just make installation easier.

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Current attachment at 24" from hinge
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Below shows current prop stick and available area for new mounting point. I have a "blueprint" of the interior structure of the wall. If it's not possible to attach into "meat" I don't mind adding a large wooden plate on the wall to support the anchor of the strut.
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Total height available in this area to attach galley end of strut. A little over 40" of height.
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So, thanks in advance for your input so I don't end up drilling a plethora of holes testing the action of a set of struts. Also, if you have a source for struts that'd be super. I have looked at this guy on ebay and he seems to still have an abundance of options... https://www.ebay.com/usr/strut-your-stuff-here?_trksid=p2053788.m1543.l2754
Tim
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Re: Gas Strut Calculation

Postby tony.latham » Sun Jul 14, 2019 9:15 pm

I buy my gas springs from McMaster-Carr. They are not the cheapest source, but they have lots of different lengths and strengths.

What did the calculator come up with? :thinking:

T
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Re: Gas Strut Calculation

Postby Aguyfromohio » Mon Jul 15, 2019 6:42 am

We bought ours at Lift Supports Depot https://www.liftsupportsdepot.com/
I find they have the biggest variety.
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Re: Gas Strut Calculation

Postby TimC » Tue Jul 16, 2019 12:25 pm

Thanks Tony and Ohio

I was outta town a few days and didn't get around to figuring this out yet. I hope to get some struts ordered this week.

Tony, I did the calculation in so far as determining extended length. I have to use your sources then to figure out what is available before I can determine how to proceed. Again, I don't understand the part of the calculation that determines weight. Seems to me that should be one of the first parameters to figure out to determine what struts are available. I'm sure there is a good reason Dan set it up that way. There are many responses saying favorable things about results. When it cools off tonight I will give it another go. My northern midwestern blood can't take too much of this near 90 degree heat.
Tim
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Re: Gas Strut Calculation

Postby DWT77 » Tue Jul 16, 2019 12:53 pm

Tim I recently had a problem with my hatch and gas struts.

Here is the thread. It might be able to help you out
viewtopic.php?f=21&t=71668
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Re: Gas Strut Calculation

Postby tony.latham » Tue Jul 16, 2019 1:53 pm

I don't understand the part of the calculation that determines weight.


Have you seen Dan's graphic on weighing the hatch? http://www.tnttt.com/viewtopic.php?f=21&t=58263

Tony
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Re: Gas Strut Calculation

Postby TimC » Tue Jul 16, 2019 1:59 pm

Oh crap! I think I just got totally discouraged into putting struts on my hatch. No offense DWT77, I'm glad you posted that. I don't know how I would react to that happening to my baby.

It's really not that difficult. I just need to do a little more work with the barbells and if that doesn't work I have an old hardhat... :oops:

Tim
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Re: Gas Strut Calculation

Postby TimC » Tue Jul 16, 2019 2:09 pm

tony.latham wrote: Have you seen Dan's graphic on weighing the hatch? http://www.tnttt.com/viewtopic.php?f=21&t=58263
Tony


Yup, that's basically how I did it (see photo on my orig post). My mounted weight of my hatch is considerably lighter than a lot of folks hatches from what I have read on tnttt. I'm surprised by that (or my weighing method is faulty).

I'm hesitatingly looking it over again after seeing DWT77's post. I'm not sure I want to do this anymore, but, I will keep looking at the calculation description until I understand what's going on. Then I will run it through you guys one more time after finding the strut to get up my courage again...
Tim
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Re: Gas Strut Calculation

Postby TimC » Tue Jul 16, 2019 3:12 pm

All, I appreciate your interest and help, but, I am going to go another route. My calculations and matching a strut to them doesn't make sense to me and this is one area that the risk doesn't justify the rewards. I have a working system that just needs a little safety item added to make me more comfortable lifting the hatch. No dis to Dan whatsoever. There are many folks using the calculator and having success. If you are interested in this modification to your TD go for it.

I think I will just figure out a "safety" pole that I can quickly slip in to support the hatch as I am maneuvering the existing supports.

Tim
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Re: Gas Strut Calculation

Postby DWT77 » Tue Jul 16, 2019 4:31 pm

TimC wrote:Oh crap! I think I just got totally discouraged into putting struts on my hatch. No offense DWT77, I'm glad you posted that. I don't know how I would react to that happening to my baby.

It's really not that difficult. I just need to do a little more work with the barbells and if that doesn't work I have an old hardhat... :oops:

Tim


Tim once I got everything figured out it wasn't bad. The whole hatch ripping off was self inflicted. That thread does have pretty good detail on how to use the calculator and of course some issues to look out for.
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Re: Gas Strut Calculation

Postby TimC » Tue Jul 16, 2019 8:22 pm

DWT77 wrote:Tim once I got everything figured out it wasn't bad. The whole hatch ripping off was self inflicted. That thread does have pretty good detail on how to use the calculator and of course some issues to look out for.


That's good to hear. Glad you worked through it. Maybe I'll pursue it again in the future, but, it'll be after a full camping season rather than at the beginning or in the middle of one.
Tim
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Re: Gas Strut Calculation

Postby danlott » Wed Jul 17, 2019 9:31 am

The reason I start with the length of the struts is that everyone’s trailers are unique. The length of the struts and the attachment points will vary greatly for each person. Once you have figured out the ideal length of the struts bases on the overall length of your hatch you have to figure out what will actually fit.

Obviously the weight of the hatch is a huge factor too. The order that you figure out the ideal strut length, what will actually fit and the weight of the hatch does not really matter. You need to figure them all out.

Then you have to do the juggling act to determine your exact attachment points and required force based on what gas struts you can actually find. It can be confusing, but if you change one thing it causes everything else to change.

I looked through your pictures. To help determine a solution for you I would need 2 additional measurements. What is the distance from your hinge to the top outer corner of your top cabinet? What is the distance from your hinge to the top outer corner of your lower cabinet/counter top?

Image

I can help you figure out what might work for you and later on you can decide if you want to do it or not.

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Re: Gas Strut Calculation

Postby TimC » Wed Jul 17, 2019 8:57 pm

danlott wrote: What is the distance from your hinge to the top outer corner of your top cabinet? What is the distance from your hinge to the top outer corner of your lower cabinet/counter top?
Dan


Thanks Dan. After looking closer I was making some assumptions on inputs in the calculator that were wrong. Below is your calculator results for my hatch using the closest strut I could find to meet the requirements. I think I have this thing figured out, but, I hope you will check my work :)

The measurements you requested...
Distance from hinge pin (living hinge) to top outer corner of top cabinet = 12.5"
Distance from hinge pin to top outer corner of lower cabinet/counter top = 34.5"

Below is what I entered into your calc. I couldn't find a close match at Mc-Carr, so,
I used a strut I found at Lift Supports Depot; 29.87: ext lgth, 11.61 stroke, 74# force https://www.liftsupportsdepot.com/lift-supports-depot-4988e32-gas-charged-lift-support/

Hatch Lgth 51" Ideal ext lgth 30.6 Number Springs 2

Stroke lgth 11.61 Ideal att. pt 9.8685

Spring att. pt 9.8685 Hatch Dd wgt 54# Req force of springs 77

I hope that all makes sense. Tim
Tim
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Re: Gas Strut Calculation

Postby jiyuu4life » Tue Aug 13, 2019 9:33 am

First of all thanks to all in this forum (TNTT). It has been a great help in my build. I am currently ready to install gas struts. The calculator has been a great help and matches other calculations that I have found. My question is the calculator says "Required Force of Gas Springs in Pounds" 95 lbs. The actual door weight is 60 lbs. What is not clear is do I need two springs at 95 lbs each or 2 springs at 95/2=50 +-? Thanks Todd
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Re: Gas Strut Calculation

Postby tony.latham » Tue Aug 13, 2019 9:39 am

jiyuu4life wrote:First of all thanks to all in this forum (TNTT). It has been a great help in my build. I am currently ready to install gas struts. The calculator has been a great help and matches other calculations that I have found. My question is the calculator says "Required Force of Gas Springs in Pounds" 95 lbs. The actual door weight is 60 lbs. What is not clear is do I need two springs at 95 lbs each or 2 springs at 95/2=50 +-? Thanks Todd


You need two. Here's my video from yesterday:



I'll be snapping on two 90-pounders when the hatch is done. :thumbsup:

T
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