Criticize my telescoping RTT platform design. (1 Viewer)

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I'm about a year out from starting to build a RTT camping trailer. Probably going to try to source a M101 or M1102 and modify the heck out of it. Need to get some welding experience under my belt before I tackle this project. Anyway, the idea I'm toying with is to have a telescoping RTT platform so that I can keep it low for towing/off road, but put it high at a camp sight. I'm experienced enough with electric linear actuators and pop-out designs to know that I don't want to go that route. Not reliable enough for off-road on what I could make on my budget. So the rough idea I have is to build a simple telescoping system but with pivot arms that would allow my RTT platform to move a little laterally while lifting one side at a time. It would only be a few inches at a time, but I'm not looking to do a huge lift. Here's some rough sketches I put together. While down and stowed, there would be locking pins keeping everything in place. When at the camp, I could pull the pins, then raise one side at a time a few perforated holes at a time. The RTT platform (green) could move along the arc of the pivot arms (orange) while the telescoping tubes (blue) are raised. This would allow the telescoping tubes (blue) to stay vertical and minimize binding in the trailer mount tubes (red). This is just a concept drawing. Nothing to scale or accounting for structural integrity yet. Likely would incorporate some easily attained struts to help with the lifting of the rather large and heavy RTT I am eying (23zero Walkabout87). Let me know what you think. Any critiques to make it better or abandon the project are welcome. Thanks.

This is also posted in expeditionportal too, if any of you are there as well.
RTT Telescoping design (1).png
RTT Telescoping design (2).png
 
I would keep it as simple as possible. While your yellow links add some flexibility, they need to be sturdy, reliable and easy to use. That will be difficult to achieve and I don't think be that useful. Also, you might consider the cargo area accessed from the tailgate on a slide out(s), as well as from the lid. Reason being that while traveling and having the tent platform in the lowered position, being able to access the contents sometimes can be difficult if limited to opening the lid - especially things in the front of the cargo area. The trailers that have the platform mounted to the lid gives the illusion that you won't have that problem - until you're camped and platform is raised and RTT deployed and staked down. So I think you're on the right track, just some fine tuning.
 
will you be able to lift and hold one side and at the same time put the pins in by yourself if you're alone? If not, maybe think of a self-locking or pawl system?
 
I agree the yellow/orange links seem unnecessary to me. I would make the top platform frame the same material as the bottoms, then just have the inserts go up into a cavity in the top frame .
 
It seems to me that if the yellow links -or something equivalent- were not there and you had the green frame directly connected to the blue risers, even with a pivot point at each corner, you could not lift the green frame one side at a time because that would bind, it would have to be lifted up while kept horizontal, which of course would be difficult to do.
 
It seems to me that if the yellow links -or something equivalent- were not there and you had the green frame directly connected to the blue risers, even with a pivot point at each corner, you could not lift the green frame one side at a time because that would bind, it would have to be lifted up while kept horizontal, which of course would be difficult to do.
Yep. That's what I'm hoping to overcome. I've seen folks do that, but seems it binds a bit and will eventually crack some welds. With this design, the vertical post can move vertically. There's still some binding that will happen, but I have an idea of adding some bungees to keep the pull direction vertical while the green is moved. This just a rough sketch for the design. Nothing is to scale and no structural integrity is considered yet.
 
One other way to do it would be not have the yellow links and instead have a slot in the little sideway tubes on top of the blue risers and have a pin ride in there. That would be fewer parts but may just be more work to fabricate so not obvious that this would be a better way to go. One thing with the yellow links though is that there will likely a fair bit of play overall given the numerous linkages, and the whole thing may just feel wobbly; but you can alleviate that a bit with having the top platform lay snugly on the risers with more of those little tabs you put in already.
 
I don't see any problems with the design. It is essentially 4 shackles. Trying to lift only one end at a time may not work. Will depend on how much compliance is in the pivot joints. It would be better if some sort of device (boat winch?) were employed to raise it all at the same time.

Let me ask this, for the small gain in height of this system, is it worth all of the trouble?

If the blue pieces are going to move within the red pieces I'll suggest that the sizes be inverted so that the larger tube isn't collecting dust into the joint. I'll also suggest that purpose made telescoping tube be used instead of tubes whose ID's & OD's might seem to work.
 
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I understand the concept of the shackles so that it doesn't bind, but the first change would be that you likely only need shackles on one pair of supports. That would allow the movement to prevent binding and the other supports would just pivot.
 
I just did a very crude analysis of this in SolidWorks and it doesn't want to move one side at a time. Both shackles want to move in parallel. I had hoped that it would move a little before binding, but I now doubt that it will. I think that you either need some sort of actuator, even if that it a simple hand crank winch, or there will need to be multiple people to lift it.

Or use some other mechanism like a X pinned at the crossing and with one upper and one lower end pinned while the other two ends slide.
 
I just did a very crude analysis of this in SolidWorks and it doesn't want to move one side at a time. Both shackles want to move in parallel. I had hoped that it would move a little before binding, but I now doubt that it will. I think that you either need some sort of actuator, even if that it a simple hand crank winch, or there will need to be multiple people to lift it.

Or use some other mechanism like a X pinned at the crossing and with one upper and one lower end pinned while the other two ends slide.
Thanks. I wish I knew how to do the same in sketchup. When looking at it, the design still doesn't pull the telescoping part straight up.the load will still be at a slight angle. I'm leaning more towards the what the person above you said, with one shackle and maybe an rod end bearing for the other mounting point
 
I think that I misunderstood the purpose of the shackles. The intent was for them to allow the telescoping posts to be at slightly different heights during the raising process? If so then they really would need to be double shackles.

Personally, I would not attempt telescoping as the alignment of all 4 posts to each other will be super-critical if the RTT isn't to wobble at either end of the travel range. If wobble is acceptable then the tolerances can be loosened and the alignment won't be so critical. I hate things that wobble uncontrollably.
Were I going to build something like this I would use an 'X' linkage where the linkage lay not quite flat on the trailer's lid when lowered and latched for travel. I would use a worm-drive, hand crank boat winch to raise and lower the RTT. It would simply pull the lower traveling ends of the X's forward to raise and slowly allow it to move rearward to lower.
 
I've been contemplating a similar setup, but using the slot method as described by @e9999. I've seen it work on another trailer I happened to see on a trip. You lift the end not slotted first, then the slotted end. Allows one person to deploy the platform.

One idea I've considered to "lock" any slop is to use a cam-lock similar to the quick-release on a bicycle hub at the joints atop each post.
 
Unless the fit of the telescoping pieces is fairly close (which could be a dirt problem) using a clamp only at one end of the female tube may not completely eliminate any play in the system. If you can grip the male tube over some significant length, then I would expect the play to be eliminated.

Bicycle QR's are attractive, but their M6 or smaller size will limit the amount of max force that they can generate to a level that I suspect is not great enough. I'll suggest bolts with 'wings' welded to their heads instead. Weld a tube to the near-side for them to pass thru and a threaded section to the far side for them to thread into. Lube the threads and the under-head with something that doesn't attract grit like motorcycle chain wax.
 
One idea I've considered to "lock" any slop is to use a cam-lock similar to the quick-release on a bicycle hub at the joints atop each post.


i think that cam and pin would be the way to go, if one or multiple cams fail there wouldnt be anything to stop it from a total collapse, the pins give another layer of safety and something solid for the platform to rest on instead of putting all of the load on the cams
 
To be clear, the cam locks I had envisioned utilizing at the slotted area, just to cut down on any rattles once deployed in the highest position. I plan to use traditional pop-pins on the upright structure - the four main posts.
 
This is the trailer I saw. He used latches to hold it down at all 4 corners, but you can see the slot design up close in the second pic. Each of the four posts has a strut/piston inside (like your rear hatch does) to assist with lifting. I wished I had taken more pics while I could but I think this conveys the "hinge on one end/slot on the other end" design well enough.

IMG_9704.JPG


IMG_9715.JPG
 
Someone likes to weld stainless steel. Unusual coupler for the US. His orientation will result in water and grit getting between the two telescoping tubes. Put the female on the top and all of those troubles go away as if by magic.

The problem that I see with the slot and the horizontal flat directly underneath it is that both are competing for control when the platform is tilted. If you did pins at one end and shackles at the other, but orient the shackles so that they are vertical when at rest, either up or down, then you could have a no slop connection between the platform and the vertical supports. In that orientation the shackles would allow more angularity than you're ever likely to want to use.
 
Coil springs down inside the 4 (red or maroon) main posts to help overcome gravity while lifting the blue extensions might ease the action of raising the tent platform. Of course it might take a few trys & some experimenting to get the right size & "finely tuned". Someone suggested a boat winch, but I'm thinking the simpler - the better.
 

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