Please review my pop top design

Factoid

Three criminal heroes
Having zero response from CCV to my many calls and emails over the last several months compounded by concerns over their installation/service reputation, I have decided to design and build my own electrically operated pop top. I have significant design and build experience over the last 30 years and feel confident in my ability to execute, but have no experience actually designing a pop top. If I went the CCV route, I wanted to install the top myself anyway so this is really about ensuring I have a solid design. All comments and questions are welcome!

First, the starting point. I have a 1976 LR 101 FC Radio body that was significantly modified by the PO. It is sound mechanically and has many desirable modifications, many on the interior. I’ve posted a couple of pictures below of the starting point.

I plan on purchasing a Fiberine top. Approximately 16” with a flat base flange. Fiberine will build my top with wood reinforcements of my choosing. I have 67” x 120” of flat roof to work with, so keep in mind that all of the dimensions in my crude drawings below will be adjusted based on he actual top and position on the roof that I choose. There’s an old saying in the military, “if the terrain doesn’t match the map, go with the terrain.” Therefore, I will adjust to the “terrain” of my vehicle.

Please look past the crudeness of my sketching to the engineering that supports it and let me know what you think. As I said, all comments and questions are welcome.i plan on starting late spring this year. Thanks!

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CoyoteThistle

Adventurer
I'm no engineer but I played around with lots of different roof lifting designs for our camper, including one similar to yours.

Have you done any force calculations? Most important to figure out is when you're in the down position, how much force from the actuator is pushing "out" (the horizontal vector) and how much is pushing "up" (the vertical vector, the one you care about to lift the roof). The smaller the angle is when closed (the acute angle opposite the 6" leg of your right triangle), the less force goes to the vertical vector. At a relatively flat angle like you have drawn, you might only be getting about 10% of the 400# of force from your actuator pushing up.

IIRC, the formula for figuring this out is pretty simple (just a sine function I think).

Super cool rig by the way!
 

Factoid

Three criminal heroes
Thanks, Coyote, I appreciate the input!

Calculating the load is a simple trigonomic vector calculation. I have all the weights except the top and the variable there will be the required wood reinforcements. I will calculate the load at various points, particularly at the closed position when the most force is required. The linier actuators I spec'ed can be upgraded to 900# for a few dollars more and most importantly, the static hold rating is the same as the push/pull rating. They also have a very reasonable wireless remote set up. Another option I'll experiment with is moving the pivot point from 50/50 to 70/30.

The disadvantage of designing one pop top from scratch is all the additional trial and error tests required to get it right.
 

mgmetalworks

Explorer
My $0.02....

I played around with a similar design to the CCV mechanism for a while and eventually abandoned the idea for two reasons.

1) It's inefficient. More lift with less actuator stroke is achievable with different designs. This may not be a big deal for some but with the actuators needed to lift the amount of weight that you'll probably have, lots of stroke means lots of time waiting for up and down. High load actuators aren't quick in other words. "Lots of time" is a relative term I'll admit...I'm just not into waiting 90 secs for something that can be done in less than 5.
2) It requires two actuators to work. I built a lifting top trailer for tailgating for a client many years ago and it had 4 actuators. It was a giant pain to keep them sync'd enough to put the top up and down without binding. After two seasons of fighting it, we ripped them out and put in a single motor system that drove gear boxes at each corner. Expensive? sort of. Complicated? not really. Bomb proof? YES! even if the motor craps out, there is a mechanical means of raising and lowering the top. You're likely looking at all the same actuators I've looked at... What are you going to do when (not if) one of them takes a dump? By yourself are you going to lift the top enough to take the weight off, disconnect the actuator that's bad and carefully lower everything down? That last few inches will be pretty heavy won't it?

I'm working on a single actuator design (and a no actuator design) for our pop tops. I looked long and hard at the way CCV does theirs and I just can't check all of our boxes doing it that way. Granted, I probably have a much different philosophy about pop tops and the weight up high on vans than others do.
 
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Factoid

Three criminal heroes
Thanks, Michael, that is great perspective and exactly the kind of input I'm looking for prior to digging in too deeply. I appreciate it!

I too considered several approaches, including the four lift approach, which I rejected for exactly the reasons you stated. Compounding my challenge is the weight with a 16” wood reinforced top and 70 pounds of solar panels and assorted lights, trim, etc. I considered a spring loaded assist, but if you've ever seen a garage door spring let go, the thought of that next to our sleeping bodies was a bit too much. I also looked at a single actuator, but as I compared the complexity and fabrication work required, returned to dual actuators. As for time to raise/lower, a 40” 400# actuator takes about 30 seconds under load which I can handle. I do remain concerned about plan B if an actuator fails and have no real plan! Compounding the failure issue is how I access the failed actuator considering my desire to not remove much of the roof to preserve the structural integrity. I'll continue to noodle on that one
 

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