8020 DIY pop top

[boywonder]

Originally Posted by Wisco150

Hey boywonder,


I will have to also figure out a size of the hinge mechanism as a whole in comparison to the fiberglass top to avoid having too small of a hinge

I’m designing the hinge to use 0.5” shoulder bolts.

I’m planning to use at least one gas strut on each side but will need to
figure out a weight estimate once I get a little bit further along. My goal is to take the fiberglass top to the local scrap metal yard and weigh it

Agreed, I was suggesting above that perhaps you could mount a very high force gas spring to each mech to help get some bias force to lift the roof in addition to the the other gas springs that you'll need. I expect you'll need some long travel struts near the front.


If you know anyone with free body diagram/static analysis skills you could do the calcs in excel; it would be a challenging but straightforward project. McMaster provides the start and end force for each strut so you will need the start and finish angles when the roof is fully down and fully up to make some plots. When you weigh the roof just assume the CG is in the center of the roof.

[Wisco150]

Hi campism, I’ve thought about vw lock mechanism for securing the top down. Once I get further along I’ll have to decide/see if that would work with how I cut the roof now roof and where the roof ribs end up.


boywonder, I’ve be looking online and reading about how to calculate placement and force needed to try and get a better understanding. Your bathroom scale idea is great and will be a lot easier than mine! My thought to check center of gravity was to set the roof of the edge of a 2x4 on a low saw horse and move it forward or back until it balances. Thanks for all the help! I’m planning to get some measurements today and start attempting to figure out the length of the arm lift mechanism that might be appropriate and then gas strut placement/length and force needed

[Wisco150]

Omen reference I’m also using is a lift bed I built using a hinge mechanism and metal bed platform from Rockler. I made the wood frame and followed the basics instructions Fromm Rockler for hinge placement. Since it’s the same lift motion as I’m looking for and although the fiberglass top is much larger I’m thinking I could scale everything to the size and weight of the fiberglass top. Here is a picture of the bed.

[boywonder]

Just assume that the roof CG is in the center...it'll be close enough. Balancing on a sawhorse will get you closer if you are motivated.

The whole objective force-wise should be to get the up forces balancing the roof's weight/down forces throughout the travel. In the case of the SMB PH roof, it's kinda balanced except for the first few inches of roof lift. The geometry of the crossbars requires huge forces at the start which are difficult to obtain.


This is a similar exercise to getting the spring preload correct on a sectional garage door. Too little and you can't lift the door, too much and you can hang from the open door and it won't pull down.


In your case doing a westy tilt type lift, your required forces are going to be roughly half, since you are only lifting one end.


I'll take a SWAG (scientific wild-ass guess) that the roof weighs 240lbs. I have no idea......

[Vanimal]

Hello Wisco, This is feeding right into my exact project. I have the Westy type hinge brackets but a cannot decide on if I want to go clam shell or straight pop top. I have one brand new never installed Fiberine for an EB that I have considered cutting down to 10 inch rise. I had EB tops and sold them all and kick my self for it. I do have a junk yard cabin boat style terraced top. It is low up front and steps up in the rear. I think the clam is much more stable in wind and deployment but I like the spacious feel of the pop top. My issue going on 4 years now is I want to do it right so I have finally poured a concrete slab the length of the side of my house to put a 2 post lift to facilitate the install. My excuse any way to get the lift. I don't think the canvas is an issue in the pop top but it can and will be in the clam style and will need focus on pattern. My grandmother use to sew and taught me so I am skilled in sewing as I use to make my kids halloween costumes and have done some car upholstery. The pop top style will be easier and the use of screw jacks will allow weight on top so I'm not worried on that. I just have to get to it.

[Wisco150]

Vanimal,

This is awesome that you are working in something similar. I love to see any updates or pictures you have for it!