2001 Suburban Pop Top Conversion

[sallf]

I used some extra aluminum square tube I had to test the concept, thinking I might need to use steel (spoiler alert, I do), sandwiched that with steel bar and picked up some longer bolts so I could bolt it to the same bolts that are coming through from my rack.







Next I drilled some rivet nuts into the top of the truck. It's a shame because I was hoping to use the original ones from the original rack but the topper ends up sitting right on them when it's centered on the roof. That's probably the biggest downside to the female mold is it was difficult to see exactly where it was going to hit the roof...at least that's what I'm blaming it on.

The rivet nuts were probably the biggest pain in the --- I've had yet on this project. If you've never worked with them you can install them by cranking down on a bolt while holding a slip nut in place with a wrench. My first issue was the slip nut they sent me was so small that I couldn't get any of the 3 wrenches I have in that size to hold just the nut. My very standard wrenches were all too thick and would grab the bolt in addition to the nut. Seriously, who has a wrench that thin!

I ultimately solved it by doubling up on nuts, but that wasn't before I tried some less successful things and ended up with some not so great rivets. There were some other complications, like the edge of an internal rib that runs down the truck which I hit it with every hole I drilled; which caused the rivet to not sit flat. I spent a few hours trying to use the dremel to cut into the rib which was exhausting. I figure worst case I'll pull out all of my interior upholstery and run bolts.






I don't have a picture of it bolted, but on the left here you'll see the super strut I ended up using. I'm hoping I'll be able to use it to mount the scissor lift, gas struts and bed platform so I don't have to drill any more holes.


(metallic original rivets, with gold new ones in the background)

I ran some silicone around the edge, attached the bulb seal and got it on top. I had to cut a couple slits to get it to go around some corners, but I think the silicone should keep me waterproof.







Lastly I crawled up through the sunroof and bolted it to the truck (my dog gets anxiety when I open a car door and she can't get in, so she's spent a lot of time in her copilot chair this project).




I'm out of pictures, but I lifted it up about 2 feet from the back and could see the aluminum tube wanting to bend. Dropped it back down and have some steel 1"x1" square tube that I can pick up tomorrow. I got the thickest gage I could find but it's possible that the steel can't handle the 3' cantilever either. I'm hoping it'll be okay but at this point I really won't know until it's up there.

My other options are 1.5"x1.5" square steel tube which I can get at 1/4" thickness (should be overkill) or more likely I'll mess with my model scissor lift and find a way to add more angle when it's lifted, which will reduce the length of my levered arms.

Looking forward to wrapping this stage up so I can get to the fun stuff like wiring, lighting, interior design and CUTTING OFF THE ROOF...which is honestly the only reason I started this project .

Appreciate any thoughts or ideas! Also I haven't been able to find anyone in the Denver/Boulder area that wants to sew canvas sides for me, so looking for a connection there if anyone happens to have one. I know boll_rig went through Colorado Camper but I can't get them to answer the phone.

 

[sallf]

I made a little more progress over the past few weeks but have mostly been educating myself on physics, forces and levers...specifically what won't work as a lifting mechanism. I was able to get my modified lift to get the topper up, but as I was inching up the gas struts to get them in the right spot, one got caught... and I didn't notice... and the torsional forces bent the lift arms.


I used two floor jacks to help me inch it up...it was a little more precarious than I'd like to admit.



And here's where it started to twist after one of the struts got caught. Not great.



Ultimately I think this design works well when it acts more like a hinge, similar to how it's used on westys or the old VW buses, and not so great when you're trying to make it lift straight up. Lessons learned and fortunately I didn't ruin anything other than the steel strips.

Anyways on to lifting mechanism #3.

Initially I was staying away from the basic scissor lift because I was having trouble finding a sliding track that I thought might work. I must not have looked that hard because Unistrut (Superstrut) makes an industrial trolley that fits in their standard track. Holy ---- wish I had tracked that down a couple months ago, could have saved some time! Here it is in the track.



So, I picked up some more 1" steel square tube and put together a standard scissor lift. I quickly tested it with my existing gas struts since I've already purchased them.



It might have worked with the gas strut, but I'm pretty tired of doing things the wrong way, so I found a couple 12v 18" stroke 1,000 lb actuators from Firgelli Automoations, moved the scissor lift back a little on the strut, and bolted everything to the strut and the strut to the roof.



One thing that surprised me is you can't move the motor side of the actuator, and since they stick pretty far out to the right, the one on the right side would have gotten in the way of the topper closing. You also can't simply flip it because the bottom comes down too far and it won't mount in the standard bracket. So I ended up stacking another piece of Unistrut and then bolting the bracket to that. Works well but the clearances are a lot tighter than I would have liked.



Next up, the horizontal bar of the scissor lift was also a little challenging to think through without a welder, but I ended up running 1/2" threaded rod through the steel tube and sandwiching the tube with a few 1.25" bearings. Locked that all down with a couple nuts and then to reinforce rod, I sheathed it with a piece of conduit and locked that down with a couple more nuts.




Also, the slot of the actuator arm wasn't deep enough to reach the mounting hole in the trolley so I had to grind it down a bit.




Feeling much better about this direction. My only major concern is the start angle of the scissor lift is going to be really low and even with 2K lbs of force, I might need to add some help to get it up the first couple inches. Not 100% sure what my weight and angles are, but If I guess 140lbs and 2 degrees to start I would need closer to 4K lbs of force (this scissor lift calculator has been great to me).

I'm thinking I could get x2 ~6" 50lb gas struts and mount them vertically towards the middle of the roof. If I put a platform on the ends, they could catch the roof as it comes down to help with those last few inches. Don't love that I might need to add more things to the already crowded space, but don't know what else to do at this point. I thought about some torsion springs but then I'm fighting the potential 4K lb lever force so it seems much easier to fight the ~140lb weight instead. Any thoughts?

More detail pictures and pictures of a new wood panel interior to come!

 

[rayra]

so you are driving on the scissor? I'd thought the scissor was just for alignment and motion control with pnueumatics providing the simple lifting force against gravity. I might not have this in my mind right, laboring under a lot of handicaps right this evening, but it seems you've built a structure and mechanism that has multiplied the force required, rather than the opposite? I would have thought in the simplest structure / mechanism you'd just have to release some catches and the pneumatics would drive it up until some physical stop / limit was reached, say in the scissor intersections, like on a mechanical pencil compass, just a bent tab or thru bolt, so the scissor can only extend so far. And if you balance / match the load and pneumatics it should just risely relatively slowly and not be a mother to force back down.
I may have misunderstood your design and very likely am not properly envisioning it.

 

[sallf]

so you are driving on the scissor? I'd thought the scissor was just for alignment and motion control with pnueumatics providing the simple lifting force against gravity. I might not have this in my mind right, laboring under a lot of handicaps right this evening, but it seems you've built a structure and mechanism that has multiplied the force required, rather than the opposite? I would have thought in the simplest structure / mechanism you'd just have to release some catches and the pneumatics would drive it up until some physical stop / limit was reached, say in the scissor intersections, like on a mechanical pencil compass, just a bent tab or thru bolt, so the scissor can only extend so far. And if you balance / match the load and pneumatics it should just risely relatively slowly and not be a mother to force back down.
I may have misunderstood your design and very likely am not properly envisioning it.

@rayra good questions, I might not have done a good job describing the evolution of my lifting mech. My original designs were using pneumatic gas springs to lift the topper, and you're right that the scissor lift, in that case, was just for alignment and motion control. This was complicated because the gas spring doesn't put its full force against gravity the whole way up. If the gas spring was perfectly horizontal when the topper was down, it would actually be pushing 0 lbs against gravity. This is not a great design for a scissor lift because finding the balance between a gas spring that is strong enough to give you good assist at low angle, yet weak enough that you can still pull the topper closed was pretty much impossible.



So, enter the new design (which is actually exactly how boll_rig did his). The new design is using linear actuators to push the legs of the scissor lift. Similar to the low angle issue of the gas strut design above, when the scissor lift is all the way down, it takes a lot more force from the actuators to fight gravity (screenshots from engineers edge).




----


My issue is that when it's all mounted, my angle will probably be pretty close to 1 or 2 degrees. So I need something that will help me reduce gravity weight for the first few inches, until the angle is 4-5 degrees and the 2K lbs from the actuators will be enough. I'm thinking a small gas strut (maybe two with ~ 50lbs of force) which catch the topper on its way down.



That's the best idea I have so far, definitely open to better ones!

 

[Hillbilly Heaven]

Curious about overhung load when open. One arm of the scissor is fixed at the bottom and the two top points get closer together as you go up. This means that when the scissor in the up position is only supporting either the front or back half of the top. One of the top points when in the up position needs to be at least at the center point of the top or ahead of it.

 

[rayra]

I see what you are doing and it is sort of what I was envisioning and envisioning as your core trouble. You've created the bind you are trying to overcome, by having the actuator push the foot of the flattened scissor. Your mechanism is basically starting up in a bind / bound position, putting a tremendous load on all those end points and the pivot axis. Wouldn't it work better if the actuator itself was one leg of the scissor, or at least driving against a point or attachment on the lifting portion, the actuator starts off with more of a lifting component to the motion (Ry?).

Or maybe use the actuator to draw the far leg of the scissor in toward the centerline and arrange the scissor armature itself to impart the vertical lift via some sort of pin or wedge that starts to open the scissor the moment the actuator attempts to move it.

I still am probably not imagining it right, btu I'm thinking of it more about leverage and moment arms and arranging things to more readily translate horizontal drive into vertical motion. Driving the foot of the scissor in seems more like you have to apply a lot of crushing force until the scissor finally gives in the only way it can. Which is going to wear it out or break it fairly quickly, I imagine. Or at least require a far beefier design than necessary. But I'm just skipping by, not really fully thinking it out. Might be barking up the wrong Newtonian tree.

There was an early point in Boll's design where I was thinking it would work by just rigging two pairs of pneumatic lifts AS the scissors. With a wire-actuated catch system built into the lid. The idea being to pull a ring, releasing catches on both sides, bracketing the pneumatics, freeing the pop top to pop. And to close you would stand in it, grab two handles fore and aft and just squat, pulling the top down until the spring-loaded / cable-released catches catch. The structure I envisioned then wouldn't / shouldn't take more than a few (20? 30?) pounds of force in either direction. Somewhat like the Liftgate on these Suburbans.

 

[sallf]

Curious about overhung load when open. One arm of the scissor is fixed at the bottom and the two top points get closer together as you go up. This means that when the scissor in the up position is only supporting either the front or back half of the top. One of the top points when in the up position needs to be at least at the center point of the top or ahead of it.

@Hillbilly Heaven that's another good question. When the topper is fully lifted the scissor lift is definitely not going to be centered under that weight. However the center point of the topper will be between the arms of the "X" (not by a lot, but it'll be in there). I'm hoping that means that the weight will not be levered.

Worst case scenario, if the weight does lever, the industrial hinges that I'm bolting to the topper should hold the weight lifting up as well as down.

Below is the best picture I have, so the "X" ends you can see there will both be fixed and the other ends will both travel (one via the trolley in the track and the other on the bearings along the top of the topper).



I'm also probably going to fix some guy lines in the front and back of the topper and they should help reduce any potential lever forces. The guy lines will cross (ex the ones on the left of the topper will pull to the right of the roof) which should also reduce torsional forces on the roof.

I'm pretty confident it will lift, the steel arms are thick, but my backup plan to that backup plan is I can always attach some metal legs when it's up and turn it into a 4 legged table. I'm hoping it doesn't come to that, but I sleep better thinking I can keep adding stuff and don't need to start over.

 

[sallf]

I see what you are doing and it is sort of what I was envisioning and envisioning as your core trouble. You've created the bind you are trying to overcome, by having the actuator push the foot of the flattened scissor. Your mechanism is basically starting up in a bind / bound position, putting a tremendous load on all those end points and the pivot axis. Wouldn't it work better if the actuator itself was one leg of the scissor, or at least driving against a point or attachment on the lifting portion, the actuator starts off with more of a lifting component to the motion (Ry?).

@rayra I like the thoughts. I think ultimately the issue is fitting 40" of lift inside a topper that's only 6" deep. Hard to do without levering some force somewhere. Making one of the legs an actuator, you'd still be dealing with that low angle force. If you think about it at 0 degrees that actuator would still putting 100% of it's power horizontally, unless I'm missing something. I did think about connecting it to the upper arm of the "X" as you mentioned but the 18" stroke would only give me about 17" of lift.

Or maybe use the actuator to draw the far leg of the scissor in toward the centerline and arrange the scissor armature itself to impart the vertical lift via some sort of pin or wedge that starts to open the scissor the moment the actuator attempts to move it.

I still am probably not imagining it right, btu I'm thinking of it more about leverage and moment arms and arranging things to more readily translate horizontal drive into vertical motion. Driving the foot of the scissor in seems more like you have to apply a lot of crushing force until the scissor finally gives in the only way it can. Which is going to wear it out or break it fairly quickly, I imagine. Or at least require a far beefier design than necessary. But I'm just skipping by, not really fully thinking it out. Might be barking up the wrong Newtonian tree.

There was an early point in Boll's design where I was thinking it would work by just rigging two pairs of pneumatic lifts AS the scissors. With a wire-actuated catch system built into the lid. The idea being to pull a ring, releasing catches on both sides, bracketing the pneumatics, freeing the pop top to pop. And to close you would stand in it, grab two handles fore and aft and just squat, pulling the top down until the spring-loaded / cable-released catches catch. The structure I envisioned then wouldn't / shouldn't take more than a few (20? 30?) pounds of force in either direction. Somewhat like the Liftgate on these Suburbans.

I like the last idea, feel like it's pretty similar to my initial thought. It runs back to that same issue though, the gas strut would need to be really strong to lift at a low angle, and when it's up and at a high angle you need a lot of force to overcome it (trust me I tried , two adults sitting on top of it didn't overcome the force). I think that design is better suited for a hinged pop similar to the westfalias or old VW buses. In those setups the force stays a little more consistent through the full lift, and then you have a big lever arm to help you overcome it.

I'm maybe foolishly, not too concerned about the wear on the parts as long as I can get the starting force under the 2K lbs that the actuators can produce. I won't be putting it up and down too often, the arms are 1/8" thick, 1" steel square tube and I'm using 3/8" bolts for everything. Again I just reducing that starting weight and I still think I should be able to get a couple 6" gas struts, mounted vertically to help me do that.

 

[rayra]

Might be as simple as human power to start the uplift as the actuator is turned on. Avoid the initial binding altogether.

I think a key to the arrangement is to have the scissors not start in a flat position, in a direct line with the actuator. If they are more of squat 'X' then the foldign action would have already begun when the actuator starts its push.

 

[sallf]

Might be as simple as human power to start the uplift as the actuator is turned on. Avoid the initial binding altogether.

I think a key to the arrangement is to have the scissors not start in a flat position, in a direct line with the actuator. If they are more of squat 'X' then the foldign action would have already begun when the actuator starts its push.

Totally. If I had had more foresight I could have probably started with 3-4 degrees. As it is I'll probably be closer to 1-2 degrees.

I've been thinking about human power. Might be the best, simplest solution. I'm going to get it mounted and cut my hole and I think that'll give me a better idea of what's feasible.

 

[CrazyDrei]

Sallf,

This is one heck of an awesome project. Your trial and error approach is very insightful to watch. Keep on positing pictures and sharing your story.

 

[sallf]

Sallf,

This is one heck of an awesome project. Your trial and error approach is very insightful to watch. Keep on positing pictures and sharing your story.

@CrazyDrei thanks! Can't say I'd recommend this approach but have definitely learned a lot. Not sure I could have done it any different though without more experience and/or better tools.

Cut the roof and finished the top of the interior, update to come!

 

[Chevrolado]

This is soooo cool! Well done so far!
Subscribing for the sheer inspiration of this custom work. So great. Well thought out and executed. Keep up the great work.

 

[sallf]

Finished up the top of the interior! Inspired by all the #vanlifers I decided to go with wood paneling for the top, really liking that look.

I started by laying 1/2" foam insulation to the top cavities. Just used duct tape to keep them in place until I could cover it all with wood.



Next up I fit a thin (1/4"?) piece of plywood to the inside as a base. Found some really light weight wainscoting-like cedar wood panels from Home Depot and snapped those together to get a dry fit.



Popped up a few sections at a time and simply glued them down with wood glue to the plywood base.



Lifted all that up, drilled a couple holes for puck lights and then glued the plywood to the fiberglass topper with with that same Loctite PL Marine adhesive I've been using for everything. I also bolted it on with the bolts coming from the roof rack. You can kinda see the holes for that in the side of the plywood below.



Glued a couple 1" thick common board runners to the side and drilled big holes so I can access the bolts coming through from the rack if I ever need to (hopefully I won't).




All went pretty smoothly up until this point. My plan was to cover those common board runners with overhanging white mdf. Idea being that the overhang would cover the gap in my wood paneling and also give me a sweet spot to mount some recessed led strip lights.

Long story short, the curvature of the roof of the fiberglass made these sides obviously not sit level. They both lean in. I probably could have solved this with 3/4" ply as my base, but that seemed like too much weight. Probably the better idea would have been adding some shims down the middle before gluing on the 1/4" plywood base...

Oh well... I ended up cutting a whole bunch of shims and gluing that to the common board. You'll also notice some thicker plywood on end to give the whole thing a little more support. Definitely not the most efficient but the white board (the strip sitting below with the tape measurer on it) seemed to have a good fit and, more importantly, sat level.



My phone must have run out of storage because I don't have a good closeup of it complete. So I'll have to jump to showing it mounted!




The front arm of the "X" (far left in the picture above) bolts to a big superstrut hinge, which bolts to a section of superstrut, which screws into the white board. The rear arms of the "X" run along a thin piece of aluminum which I screwed onto the whiteboard.

I used my floor jack to help it get started, and after it got up a few inches, the actuators were able to lift the rest of the way. My mini-gas struts get in tomorrow so I'll be able to test my assisted lift at the start! I have an idea...we'll see if it works.

With it up, I also taped out where I want the hole to be...



I drilled 1/2" holes in the 4 corners, as the rounded edges should make it a little stronger, and got to cutting...



This was a little scary since it's probably my final point of no return on this project...might have blacked out through part of it, but came out pretty good!



I know boll_rig went a full section further in his cut, which probably added 3-4 feet. I'm still considering this, but wanted to stop here and think about it a little more.

What do you all think? Should I add more space to stand and have to deal with a modular bed piece, or should I leave it as is and have an easier time with the bed?

Feels good to finally be able to stand up in the back!

 

[RPhil]

Awesome progress. Gives me ideas for the future of my Excursion.