Teardrops n Tiny Travel Trailers

tony.latham wrote:

The first set of struts were too light, the second were too strong...

Did you get them from McMaster? They haven't blinked on returns in the past.

T

Yes, I did get the struts (and a lot of other hardware for the build) from McMaster. They may not be the least expensive, but they have an incredible selection, quick delivery, and great customer service including returns. I kept the "too strong" pair of struts thinking that the struts may lose lifting capability over time. However, so far, the middle selection has held up well although they do get a little wimpy in cold weather.

aggie79 wrote:

Tom&Shelly wrote:Did you use Dan's calculator to find the attachment points and spring force?

Tom

Tom, I didn't use the calculator. I did the "Kentucky windage" method of lifting the hatch, guessing the weight, and dividing that weight by two (one for each side). This gave a rough starting point for the strut rating. The first set of struts were too light, the second were too strong, and the third set was just right.

The calculator may eliminate the guesswork and expense, but given my experience, I would also consider a strut length that is available in a range of strut ratings. If you have to increase or decrease the rating, you don't want to also have to move the mounting points.

Sounds like good advice! Thank you Tom.

Tom

aggie79 wrote:

Tom&Shelly wrote:Did you use Dan's calculator to find the attachment points and spring force?

Tom

Tom, I didn't use the calculator. I did the "Kentucky windage" method of lifting the hatch, guessing the weight, and dividing that weight by two (one for each side). This gave a rough starting point for the strut rating. The first set of struts were too light, the second were too strong, and the third set was just right.

The calculator may eliminate the guesswork and expense, but given my experience, I would also consider a strut length that is available in a range of strut ratings. If you have to increase or decrease the rating, you don't want to also have to move the mounting points.

This is how I did mine too. I got lucky the first time. But I did try 3 or 4 different mounting locations. One spot did not work at all, wouldn't hold the hatch open. Moved 6" and all is good. Like was said in a few post up the it takes a little effort at the start of opening it but then gets easier. My wife can do it now that I have a handle to lift from.

Todd

KTM_Guy wrote:

aggie79 wrote:

Tom&Shelly wrote:Did you use Dan's calculator to find the attachment points and spring force?

Tom

Tom, I didn't use the calculator. I did the "Kentucky windage" method of lifting the hatch, guessing the weight, and dividing that weight by two (one for each side). This gave a rough starting point for the strut rating. The first set of struts were too light, the second were too strong, and the third set was just right.

The calculator may eliminate the guesswork and expense, but given my experience, I would also consider a strut length that is available in a range of strut ratings. If you have to increase or decrease the rating, you don't want to also have to move the mounting points.

This is how I did mine too. I got lucky the first time. But I did try 3 or 4 different mounting locations. One spot did not work at all, wouldn't hold the hatch open. Moved 6" and all is good. Like was said in a few post up the it takes a little effort at the start of opening it but then gets easier. My wife can do it now that I have a handle to lift from.

Todd

Good information Todd, thank you. I'm looking to design the struts so they help hold the hatch closed--I think that's an advantage to help keep dust and water out (as long as they aren't putting to much force on the seals). We'll design in a handle to make the initial lift easier.

I've enjoyed looking into how the struts work, by looking at Dan's spread sheet and hearing how you and others have designed yours. It's a bit of practical mechanical engineering. To paraphrase (and clean up) an old Monte Python joke: I'm really an electrical engineer, but this is my Summer vacation!

Tom

Good information Todd, thank you. I'm looking to design the struts so they help hold the hatch closed--I think that's an advantage to help keep dust and water out (as long as they aren't putting to much force on the seals). We'll design in a handle to make the initial lift easier.

I think it's a big deal that the struts are working to keep the hatch closed. You wouldn't want the latch system to stop working while you're barrelling down I-90. It'd spoil your mileage.

And I think a handle is a must.

I probably spent about thirty hours looking for one that I liked for this build. Here's the one I ended up with:

https://www.ebay.com/itm/Marine-Stainless-Steel-Grab-Handle-9-Oval-Safety-Hand-Rail-for-Door-Bath-Boat/223485096795?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649

It's got a nice base to spread the force. I'll add a couple of T-nuts on the inside.

Tony

tony.latham wrote:

Good information Todd, thank you. I'm looking to design the struts so they help hold the hatch closed--I think that's an advantage to help keep dust and water out (as long as they aren't putting to much force on the seals). We'll design in a handle to make the initial lift easier.

I think it's a big deal that the struts are working to keep the hatch closed. You wouldn't want the latch system to stop working while you're barrelling down I-90. It'd spoil your mileage.

And I think a handle is a must.

I probably spent about thirty hours looking for one that I liked for this build. Here's the one I ended up with:

https://www.ebay.com/itm/Marine-Stainless-Steel-Grab-Handle-9-Oval-Safety-Hand-Rail-for-Door-Bath-Boat/223485096795?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649

It's got a nice base to spread the force. I'll add a couple of T-nuts on the inside.


Tony

That is a nice handle wish I saw this before I put mine on. Maybe a down the road upgrade. One of the things I forgot was backing for the handle. By putting is low on the hatch I was able to hit some solid wood.

Todd

tony.latham wrote:And I think a handle is a must.

I probably spent about thirty hours looking for one that I liked for this build. Here's the one I ended up with:

https://www.ebay.com/itm/Marine-Stainless-Steel-Grab-Handle-9-Oval-Safety-Hand-Rail-for-Door-Bath-Boat/223485096795?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649

It's got a nice base to spread the force. I'll add a couple of T-nuts on the inside.

Tony

That's similar to the one I used...and I'll "second" the need for a good handle with the backing substantial enough to anchor the handle.

I ended up going with shower handles for all of mine. Probably could have went with smaller ones.







Should be able to get back to the hatch this weekend. Was out of butyl tape. Finally got some. That and we finally got some break in the rain here in Oklahoma

I can't order springs until I get the hinge back on and verify my dead weight. I am pretty sure it is correct but I don't want to go through all of this again. I think with everyone's help/advice the hatch should be pretty solid by the time its done.

Started back on the hatch today. Got the hinge back on then a storm rolled up on me. This is what I got so far

Cleaned the old butyl tape off of the hinge and teardrop. Came right off of the hinge with a putty knife.




Cleaning off the teardrop side


On a side note I had thought about making quick disconnects for all of my electrical connections. In case I ever needed to take the hatch off. I figured meh I probably won't ever need to do that. It was a little windy so I had to strap the hatch up since I couldn't remove it all of the way. Now I wish I would have made the disconnects


I replaced the screws on both sides of the hatch (#10 1 1/2" long) Also added some 3M 4200 to the screws before I replaced the screws





This is when the storm came in. I managed to get this weighed real quick. My dead weight at this position came in at 80 lbs which previously I had it at 100 lbs



That is where I had to stop



I did input the new dead weight into the spreadsheet and then looked for some gas springs close the new force.

I found this one on McMaster https://www.mcmaster.com/4138t63
Extension Force = 100 lb
Extended Length 35.43"
Compressed Length 19.29"
Stroke Length 16.14"
Compression Force 136 lbs.





Then I found this one at Lift Supports https://www.liftsupportsdepot.com/lift- ... t-support/
Extended Length: 36.00
Stroke C [in]: 15.20 (Changed the stroke length in the spreadsheet see below)
Compressed Length B [in]: 20.00
Force (Lbs): 120

What you are doing looks right to me Wayne.

I'd noticed earlier that those McMaster Carr struts only come in 50 lb force increments, but with the spread sheet showing your requirement for 106 lbs, and with the 50 lb safety factor built in, wonder if 100 lbs would work okay? (I suspect so, but realize, if it doesn't, it means re-positioning your struct mounts.) Hope Dan offers his views...

Tom

wonder if 100 lbs would work okay?

Tom I was thinking it might as well

(I suspect so, but realize, if it doesn't, it means re-positioning your struct mounts.)

I was wondering since I could only find 36" gas springs instead of the recommended 39" how that changes the mounts?

The Ideal gas spring length isn't 60% of the hatch length at 36"

Which that should change the ideal attachment point 85% of spring stroke as well

DWT77 wrote:

wonder if 100 lbs would work okay?

Tom I was thinking it might as well

(I suspect so, but realize, if it doesn't, it means re-positioning your struct mounts.)

I was wondering since I could only find 36" gas springs instead of the recommended 39" how that changes the mounts?

The Ideal gas spring length isn't 60% of the hatch length at 36"

Which that should change the ideal attachment point 85% of spring stroke as well

The attachment points and required force are based on the length of the struts you purchase. The overall hatch length and ideal gas strut length are not used in the calculation for the required force. They are only used to determine the ideal strut length. The attachment points are calculated based on the overall length and stroke of the struts you purchase. The lower attachment point should be equal in length from your hatch hinge point to the overall length of your struts. The upper attachment point should be 85% of the stroke length from the hatch hinge point. The strut force required is calculated based on the dead weight of your hatch and the calculated attachment points of the struts that you purchase.

The 100 lb struts should work. Instead of having a 10% safety factor you will be closer to a 5% safety factor.

McMaster https://www.mcmaster.com/4138t63
Extension Force = 100 lb
Extended Length 35.43"
Compressed Length 19.29"
Stroke Length 16.14"

Based on the information that you provided on the 100 lb struts your attachment points should be as follows:

Lower attachment points on the galley walls: 35.43" from the hatch hinge point
Upper attachment points on the hatch: 13.72" from the hatch hinge point



These attachment points should allow for the proper lifting force and the struts to be compressed 85% when the hatch is fully closed.

The only other thing I would check is to get a longer prop stick and try to measure the dead weight of the hatch from the ground level. In your picture it looks like your prop stick is at an angle while you are measuring the dead weight. I am not sure how that would affect the true dead weight, but it would be easy to verify. The prop stick should be plumb to give the most accurate measurement.



Dan

tony.latham wrote:

Good information Todd, thank you. I'm looking to design the struts so they help hold the hatch closed--I think that's an advantage to help keep dust and water out (as long as they aren't putting to much force on the seals). We'll design in a handle to make the initial lift easier.

I think it's a big deal that the struts are working to keep the hatch closed. You wouldn't want the latch system to stop working while you're barrelling down I-90. It'd spoil your mileage.

And I think a handle is a must.

I probably spent about thirty hours looking for one that I liked for this build. Here's the one I ended up with:

https://www.ebay.com/itm/Marine-Stainless-Steel-Grab-Handle-9-Oval-Safety-Hand-Rail-for-Door-Bath-Boat/223485096795?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649

It's got a nice base to spread the force. I'll add a couple of T-nuts on the inside.

Tony

Shelly picked this one:

https://www.amazon.com/dp/B071HSRYHZ/re ... 9CbW9MXQDZ

It is wider than our hands, and I like the 4 screws/bolts to spread the load. Plan to add blocking for it tomorrow.

Tom

Tom&Shelly wrote:

tony.latham wrote:

Good information Todd, thank you. I'm looking to design the struts so they help hold the hatch closed--I think that's an advantage to help keep dust and water out (as long as they aren't putting to much force on the seals). We'll design in a handle to make the initial lift easier.

I think it's a big deal that the struts are working to keep the hatch closed. You wouldn't want the latch system to stop working while you're barrelling down I-90. It'd spoil your mileage.

And I think a handle is a must.

I probably spent about thirty hours looking for one that I liked for this build. Here's the one I ended up with:

https://www.ebay.com/itm/Marine-Stainless-Steel-Grab-Handle-9-Oval-Safety-Hand-Rail-for-Door-Bath-Boat/223485096795?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649

It's got a nice base to spread the force. I'll add a couple of T-nuts on the inside.

Tony

Shelly picked this one:

https://www.amazon.com/dp/B071HSRYHZ/re ... 9CbW9MXQDZ

It is wider than our hands, and I like the 4 screws/bolts to spread the load. Plan to add blocking for it tomorrow.

Tom

A good find.

T


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