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Jocklandjohn

Lifting roof mechanism engineering advice please!

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I'm altering the lifting roof I made on my 110 to have hard sides (rather than fabric) so I can use it in winter. As part of the alteration I'm going to use linear actuators to raise the roof. However the method of attachment and mechanism to do this needs some engioneering input from an adult!

I dont have space to use the actuators directly attached to the upper and lower sections because there's not enough space. So it needs some form of scissor or other design internally. The space between the upper and lower sections of roof is only 3 inches and thats just enough to take the motor body for the actuator so I know they'll fit in the gap lying down (horizontal to the roof).

My engineering query is which method of lifting is the most efficient, either:

1) a scissors type action with all the points of attachment fixed and pivoting

or

2) a C type lipped steel channel laid horizontal with a wheel mechanism inside with the actuator pushing it forwards and as it rolls forward it pushes a rod up thats attached to the celing thus opening the roof.

Or maybe something else I've not thought about?

 

There is a possibility to mount them externally where they could work vertically, attached to the lower and rasiing sections with a single fastening at each end, but of necessity they would be hidden and awkward to get at if they failed so I'd rather have them internal and accessible so I can easily unhitch and use manually if needed.

I've not undertaken anything of this nature before so uncertain as to the stresses involved and how to best manage them for safety and functionality. Actuators I got are 18 inches long and 330lb push/pull (using 2).

Any thoughts?

Flysheet Van.001.jpeg

Flysheet Van.002.jpeg

Edited by Jocklandjohn

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I also don't know much about them, but I think I'd go with the second one. But have some springs to push it up a couple of inches to get it going. Ones just enough to lift the roof a bit, but weak enough to be able to overcome them with some over-centre catches to hold the roof down for travelling.

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Thanks. Yes the springs is part of what I've been contemplating too because the current setup has gas struts (x4) but because they start their operation 'lying down' they dont actually apply any force until the roof is lifted several inches (by my shoulder) after which they whuffle up nicely. I guessed it would be the same problem with the actuators. I did actually consider a couple of small actuators to initially move the roof up to start (& finish) but once I sat down and thought through how they syncronize with the main ones it got way too complicated.

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Smaller actuators just to give a little push upwards to start with wouldn't be hard to do. But it is a hell of a lot easier to just put a couple of springs in place (thinking something like a valve spring sort of size or even smaller).

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Using option 2 you could get clever and design in a slider on the end of the actuator where it attaches to the lever rod with a little ramp, so for a couple of inches of travel before it starts lifting via the lever, it's pushing the roof upwards on the ramp. You could use the same mech to lock the roof in place once it's down with an upside down ramp. I'm not near my pc or I'd do a cad drawing for you. Hope it makes sense! 

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1 minute ago, lo-fi said:

Using option 2 you could get clever and design in a slider on the end of the actuator where it attaches to the lever rod with a little ramp, so for a couple of inches of travel before it starts lifting via the lever, it's pushing the roof upwards on the ramp. You could use the same mech to lock the roof in place once it's down with an upside down ramp. I'm not near my pc or I'd do a cad drawing for you. Hope it makes sense! 

I like that a lot! :D 

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12 minutes ago, landroversforever said:

Smaller actuators just to give a little push upwards to start with wouldn't be hard to do. But it is a hell of a lot easier to just put a couple of springs in place (thinking something like a valve spring sort of size or even smaller).

I thought that but then thought through whats required - once the small ones start moving the big ones need to move too otherwise the small one is 'fighting' against the static one. Some electronics are required to sync the operation of all of them. I fear its not as eay as it seems!  (might be wrong though!)

 

6 minutes ago, lo-fi said:

Using option 2 you could get clever and design in a slider on the end of the actuator where it attaches to the lever rod with a little ramp, so for a couple of inches of travel before it starts lifting via the lever, it's pushing the roof upwards on the ramp. You could use the same mech to lock the roof in place once it's down with an upside down ramp. I'm not near my pc or I'd do a cad drawing for you. Hope it makes sense! 

I think I'm sort-of vaguely getting where you're going but would need a rough drawing to fully get my head round it!  Dont need to CAD it just a pencil sketch would let me understand. Is 75mm enough space for what you're suggesting?

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3 minutes ago, Jocklandjohn said:

I thought that but then thought through whats required - once the small ones start moving the big ones need to move too otherwise the small one is 'fighting' against the static one. Some electronics are required to sync the operation of all of them. I fear its not as eay as it seems!  (might be wrong though!)

I don't think they'd fight much.... you literally just need it off the surface for when the main ones aren't generating any lift.

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I was envisioning two separate buttons - one to start the small ones and then another to start the big ones. Howver that meant the big ones would be 'passive' during the initial action of the small ones. If both sets operated off the same switch then they'd all go together (which is fine) but when the small ones reached the end of their actuation I couldn't figure out whether all of them would stop or whether the small ones would stop and the big ones keep going until they'd reached the end of their stroke. (they auto-stop at the end of their action). What really did my head in was trying to figure out what would happen on the way down - I guessed the small ones would start to go down as soon as the switch was reversed which would mean that the big ones would have no 'buffer' at the end of the action when the roof is almost closed as the small ones woould have long since retracted.

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You only need a small nudge from the little ones then you can retract them straight away.

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But you may need a bigger nudge down from the little ones, the long ones may not have enough torque when right down at that angle.

I think this is what is being suggested by lo-fi is that the first part of the channel you have drawn a cross section of would be bent downwards, the actuator end would have a bit of teflon on it, and that acts as a wedge to lift the roof the first bit. Then, as it comes over the kink in your channel, it will contact the wheels (or through the middle of the wheels....) of the upright and start pushing on that. There's no need for the rod and the actuator to be physically attached...

You'd have to fiddle with the shape of the end 'pusher', to make sure it doesn't bind, or stop the wheels on the rod from rolling, but reckon it is doable. The roof, will also need something for the teflon to slide against. And you will need to mount the actuator at the same height as the horizontal section of the channel to avoid binding (well most likely).

Depending on where the end of the actuator is, and the room you have, you could get a few inches of lift this way.

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Where's SimonR when you need him? This is exactly his sort of thing!

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58 minutes ago, Bowie69 said:

But you may need a bigger nudge down from the little ones, the long ones may not have enough torque when right down at that angle.

I think this is what is being suggested by lo-fi is that the first part of the channel you have drawn a cross section of would be bent downwards, the actuator end would have a bit of teflon on it, and that acts as a wedge to lift the roof the first bit. Then, as it comes over the kink in your channel, it will contact the wheels (or through the middle of the wheels....) of the upright and start pushing on that. There's no need for the rod and the actuator to be physically attached...

You'd have to fiddle with the shape of the end 'pusher', to make sure it doesn't bind, or stop the wheels on the rod from rolling, but reckon it is doable. The roof, will also need something for the teflon to slide against. And you will need to mount the actuator at the same height as the horizontal section of the channel to avoid binding (well most likely).

Depending on where the end of the actuator is, and the room you have, you could get a few inches of lift this way.

I've only got 70mm of space between the upper and lower sections, and thats barely enough for the motor casing on the actuator. SO whatver mechanism is used needs to fit within that. If I take the timber lining off the lower section I might gain another 50mm.

What I do have is clear space at either end rear quarter. There's a void left between the 'furniture' at the end and the quarter lights/rear panel. Theoretically could fit a vertical actuator in there to give initial lift. I did toy with idea of putting a longer one in but the amount of angle it needs as the roof swings up is too much for the avalable space, but would be ok for a short push I reckon.

 

Flysheet Van.001.jpeg

Flysheet Van.002.jpeg

Flysheet Van.003.jpeg

Edited by Jocklandjohn

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Honestly, I'm quicker with CAD than I am with a pencil. This is what I had in mind - would fit in 70mm. Plenty of room for refinement, it's literally just a sketch :)

1.PNG

2.PNG

3.PNG

4.PNG

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Same thing, different take :) Though it does overcome the misalignment issue nicely, if there was to be one.

But yes, my solution could be made to work in the same way, reason for teflon was making it all nice and slippery, therefore easier on the actuator. :) 

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Bugger thats clever (and quick!). Ok I see the idea with the ramp - I was having trouble picturing how it would function. I llike the integral locking pin too!  Aha right need to get some serious thinking done here. Thanks so much for taking the time to do that!

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There's almost nothing as exciting as a problem with tricky constraints to solve. Bowie and I clearly thinking on the same lines :)

Keep us posted how you get on! 

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Will do! I'm currently getting the outer frame welded up. I'm tacking and my mate is doing the proper job with the expensive welding kit when he has time. Its basically utilising the roof with an inverted C channel to hang the sides off.  All will become clear if its a goer!

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It was inspired by this german vehicle I saw but with lower sides (for reasons of sealing onto the existing work I've done rather than a new build).

bdy201793774.jpg

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Have you seen how T5/T6 California roofs operate?

I had a genuine vw reclaimed caly roof fitted to my T5 van this summer it works on a pretty simple closed loop hydraulic circuit, the roof locks into the down position pretty much like you've described in your sketches, i.e. the lift cylinder locks the roof down when fully retracted.

I'd drop this chap a mail see if he has a motor/pump/cylinders assembly not attached to a roof, if anyone can get you one its him. - no fancy controls needed, just a switched polarity 12v supply.

https://www.kernowtransporters.co.uk/

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Back on the lifting mechanism again and have an idea and wonder if anyone can see any obvious flaws in it.

The idea that lo fi kindly drew in his CAD software is the route I'm exploring (bottom one) which is an elaboration of the pic I posted further up the post.

My main problem is I have no proper engineering kit to fabricate anything complicated, so as I did with my lifting roof I'm being creative with commercially available stuff.

What I've been looking for is an industrial track I can use to allow the lower end of the lifting strut to roll along - the track preventing it from being pushed sideways by the linear actuator. I had a brainwave and looked at hanging door track and hey presto came across this which is the correct height to fit the space I have, is not too expensive, and seems robust enough.

Basically I screw the hanging track 'upside down' onto the lower section of the roof, insert wheeled hanger and make a simple strut to lift and fastening for the end of my linear actuator. The roof weight is around  100kg, linear actuators 1500N push/pull each (x 2) and track/wheels rated for 75kg (in hanging mode).  Wheeled bracket usefully has a threaded centre to allow me to connect to, and I'll have to come up with some form of metal 'shoulder' designed into it to straddle the casting (to prevent it rotating.

The bracket should also be able to incorporate the 'flying wedge' idea lo fi came up with so I get that initial lift in the horizontal plane to take some of the pressure of the initial lift. 

Thoughts?

brundle.jpeg.57fe57f1bac74ac03527badef7e6c5f5.jpeglight-duty-top-track-2-metres.jpg.edb2631558219e2df8a17c8dd65adf9d.jpg4-wheel-light-duty-hanger-k075.jpg.a306283ffe715fbea3150f63720adbd0.jpg

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Shame you're so far away as I have some sliding track and wheeled units from a very very robust travelling ladder system that got scrapped...

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1 hour ago, FridgeFreezer said:

Shame you're so far away as I have some sliding track and wheeled units from a very very robust travelling ladder system that got scrapped...

Thanks for thinking of me anyway!  Dimensions are critical and the stuff I've linked to might just be wide enough/small enough to fit the gap I have available (out of all the stuff I've been looking at). Need to do some serious measuring, I've taken the fabric sides off yesterday so I can see in the gap properly, so a wee bit of measuring and scribbling is on the cards!

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What about 2020 aluminium extrusion or similar, tonnes of that being used in 3D printers (google makerslide for examples), much lighter and you can get all the bearings, brackets, etc. to match it.

KJN do Rexroth and "almost" rexroth in a variety of sizes mail-order cut to length, it's surprisingly strong (and has well defined specs so you can work it out properly).

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Well I was unaware of that treasure trove of stuff! Thanks for the heads up - will stick my head into it and see what I can unearth, but that looks really interesting. Who knew!

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