Not quite. We have 600 litres (150 gallons) of fuel, and 400 litres (100 gallons) of water, pull out kitchen, two spare wheels and tyres, (385/65 R22.5) and other storage boxes still on the truck.
Slide-outs - any reason to not use a DIY dovetail slide
- Thread starter SPF40plus
- Start date
Not quite. We have 600 litres (150 gallons) of fuel, and 400 litres (100 gallons) of water, pull out kitchen, two spare wheels and tyres, (385/65 R22.5) and other storage boxes still on the truck.
ITTOG
Well-known member
Not to mention empty trucks off-road all the time.
So, I'm looking at an alternative to the Dovetail Slide.
Its very simple, can be serviced easily, and should not require much lubricant to make it work. I want the mechanism to support the slide out without deploying the legs (while the camper is on the truck) and it needs to support the full weight of the camper which the legs are deployed and the camper is lifted off the truck. After some testing on some 1"x1" SHS I think there will be good transfer of torsional loads between the two parts of the slide, which will help to stop the box from twisting. FYI there will be more structure on the open end of the beams, but i've left this out for clarity. The angle is 125mm x 125mm x 10mm (5"x5"x3/8"). Here are some pics:
Closed:
Open:
And a close up:
Red Arrow: there will be either a brass or UHMWPE sheet between the plate and the internal SHS.
Blue Arrow: the lower plate is the stop, as it runs into the angle on full extension.
Green Arrow: 150mmx50mmx3mm (6"x2"x1/8") RHS is welded to ends of tubes and is the main structure for the slide out.
I'm hoping that this will allow the beams to resist loads in both directions, downward force on the camper when extended and without the legs being deployed, and then upward force from the jacking legs.
The other key feature is that it allows the floor to be fastened directly to the double beams, and for all fixtures to be bolted down and permanently fixed to the structure of the frame.
Any comments are welcome.
Its very simple, can be serviced easily, and should not require much lubricant to make it work. I want the mechanism to support the slide out without deploying the legs (while the camper is on the truck) and it needs to support the full weight of the camper which the legs are deployed and the camper is lifted off the truck. After some testing on some 1"x1" SHS I think there will be good transfer of torsional loads between the two parts of the slide, which will help to stop the box from twisting. FYI there will be more structure on the open end of the beams, but i've left this out for clarity. The angle is 125mm x 125mm x 10mm (5"x5"x3/8"). Here are some pics:
Closed:
Open:
And a close up:
Red Arrow: there will be either a brass or UHMWPE sheet between the plate and the internal SHS.
Blue Arrow: the lower plate is the stop, as it runs into the angle on full extension.
Green Arrow: 150mmx50mmx3mm (6"x2"x1/8") RHS is welded to ends of tubes and is the main structure for the slide out.
I'm hoping that this will allow the beams to resist loads in both directions, downward force on the camper when extended and without the legs being deployed, and then upward force from the jacking legs.
The other key feature is that it allows the floor to be fastened directly to the double beams, and for all fixtures to be bolted down and permanently fixed to the structure of the frame.
Any comments are welcome.
Attachments
Do you think the idea in the last post would be any better? My thought is that instead of binding like a dovetail likely would, this would create a jacking force instead. And, if for example the floor was twisted because one corner had drooped, then it would likely lift that corner. The downside being that the wall thickness needs to be thick enough so it has the strength to make that happen, and not dimple or kink.
I hope the pictures make the plan clearer. No box though - it makes it hard to see the mechanism.
Without getting into a ton of math that would probably just end up proving my incompetence, I would say that the 1” tube seems too little to me. If I was building my own with a design similar to yours, I would be thinking something like 1x2 or better 1x3 with probably a wall of 0.083 or something like that. My thought is that the overall greater height would result in less material used for greater stiffness and thus longer span between crossbars… less weight and more strength.
There are some trade-off considerations. I don’t think you said how thick your theoretical 1x1 was, but if it was, say 0.250”, you could definitely drill and tap it and not need captured nuts or anything like that, possibly making the build easier, but I personally like captured nuts or flag nuts for the flexibility of assembly position they provide.
A taller cross section with longer spans might also allow the legs to fold up underneath for storage, although I know you mentioned making the floor as thin as possible.
How are you planning to power the mechanism? Lead screw / linear actuator? Hydraulic? Pneumatic? Angry hulk pull? It might make a difference.
Given all the problems I can anticipate with slide outs, I might be tempted to get crazy and make something fold out or down instead. I guess it depends on the desired use of the space inside.
Have you sketched a floor plan yet?
There are some trade-off considerations. I don’t think you said how thick your theoretical 1x1 was, but if it was, say 0.250”, you could definitely drill and tap it and not need captured nuts or anything like that, possibly making the build easier, but I personally like captured nuts or flag nuts for the flexibility of assembly position they provide.
A taller cross section with longer spans might also allow the legs to fold up underneath for storage, although I know you mentioned making the floor as thin as possible.
How are you planning to power the mechanism? Lead screw / linear actuator? Hydraulic? Pneumatic? Angry hulk pull? It might make a difference.
Given all the problems I can anticipate with slide outs, I might be tempted to get crazy and make something fold out or down instead. I guess it depends on the desired use of the space inside.
Have you sketched a floor plan yet?
Alloy
Well-known member
I've seen full wall slides but they were a rectangular box without no step up.
Fabricating and keeping 5 beams aligned... you'll be having nightmares about alignment.
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Sorry for the confusion regarding the 1" x 1". This was just a test I did to see if the arrangement above would transfer torsional loads. Which it does reasonably well. With the larger tube, there should be less losses (better transfer of forces) from the same tolerances.
The arrangement in the images above uses 75mm x 75mm (3" x 3") SHS. I'm hoping once I do more maths that 65mm x 65mm (2.5" x 2.5") SHS can be used.
I like captured nuts too, I generally like the type which are installed like a pop rivet (rivnuts) because if they get stripped out, you can easily drill them out and install a new one. They can be hard to install in tight spaces though. In these areas I tend to weld a thick plate onto the tube and drill and tap that plate. This can save a massive amount of weight. I'll likely also use thin wall tube where possible (like 1/8") and weld plates on where the loads are highest so the tube doesn't bend or kink.
I am wondering if 75mm x 50mm (3" x 2") would be a better option for the two outer tubes, as they will save some weight and take up less space in the floor cavity (more space for insulation - for both temperature and to keep dust out).
If I have to I'll use ball screws. I like the concept of angry hulk pull though - unfortunately I don't think i'm tall enough to make that work.
But my preference is to use two roller chains (think motorcycle size chain), with sprockets mounted at each side of the main floor, and the chain attached to the slide out. This will make me stand at the rear of the truck and look at the place that I'm extending the slide out into. I'm hoping that a crank with a 20:1 ratio will be enough to operate the slide manually. This would mean that there is between 300 - 400 lbs (140 - 180 kg) of force to open and close the slide out.
Still arguing about the floor plan with the better half, but yes generally I know where everything is going. Most of the heavy stuff is above the rear axle, except the water tank, which is just behind the goose-neck in the picture. The slide out has the double bed, shower, toilet, and the dinette in it.
Have you considered the complexity of the drain line required to put the shower and toilet into the slide out? I would personally try and design something without a moving drain line, as that sounds worse than a slide when it goes wrong. Even with a cassette toilet, I assume you will want some sort of drain to a grey tank.
I’ll have to think about the rest.
Thanks for the comment, yes the grey tank and drain line in the slide out would be bad. At the moment I am looking at not having a grey tank, but am doing my research to see if there is anywhere we can't go (that we want to) without one. A local company is making prototypes of grey water recycling units that releases filtered water (not suitable for drinking), so the tank only has to be 10L (2.5 gallons) in size, and has a 12/24v pump that drives it. I'm on the list to try one of these.