Aftermarket High Top Internal Structures. Strength/differences?

[eporter]

So it seems like 99% of aftermarket high tops/roofs are made of fiberglass. Some have wood supports molded in, some don't. It seems Fiberine and others offer the option of fiberglassing in wood inserts for rooftop solar panels/cargo racks, etc.

I recently saw this pic of a gutted ambulance high top, and really liked the added steel angle structure. I'm not sure how much strength this would really offer in a roll-over, but it's got to be better than just the fiberglass high top that's screwed/bolted to the existing van roof. I know the ambo boxes are rated for a roll-over, so I'm assuming this construction is for the same?

I've seen another aftermarket conversions with basically a mini roll-cage kind of construction/support in the high top area.

How much strength is really needed on these high tops? Does adding a tube structure offer enough benefits to offset the added weight high up?

 

[eporter]

 

[gmtech]

i think the idea is in a roll over it doesn't crush and you can still open the doors. as is why all class 3 and so ambos are made with tube aluminum and very strong. not like motor homes and other rv which are made of paper and twigs

 

[Smoker]

Near me in Massachusetts the only places I could find that would install a fiberglass hard top were converters for wheelchair and commercial transportation vans. They told me they would only install tops with steel roll cages because it was required by law. I don’t know DOT rules but that was their policy. The cages were custom fabricated and very beefy. But they also significantly reduced headroom in vans where a factory headliner was reinstalled. You could recapture a little space by carpeting around the frame.

 

[WVI]

I tend to think like Smoker. Comercial use would require more strength. It wouldn't be much in a full roll over unless it was tied all the way through the ody, maybe to the frame. But, that strength on top, would only need to be there for a split second to possibly stop a full rollover and thats hugh.

 

[Corneilius]

My Mark III top has a 1" square tube bar that goes up and over, connecting the body on both sides. Its roughly above the side doors. It doesn't inspire a lot of confidence but its better than nothing I guess. The top itself is a fiberglass honeycomb that is actually quite beefy.

 

[kevman]

Our raised top is essentially a sheet in the wind. We took out the upper cabinets to do some work on it and the entire top just marshmallows down the road. Every time you hit a bump you can see the side bulge out and the top come down. So how much strength is needed? Apparently not a lot. Haha. That said, I try not to drive it at the moment until I can get some cabinets back in to hold the top up. I'm also going to try and tie in roof rack mounts for future use like solar to the main body.

 

[eporter]

Kevman looks like you've got a huge bubble top, those must get floppy without any internal bracing!

I'm pretty sure most conversion vans are similar; just fiberglass and some wooden cabinets/bracing?

 

[jblaze5779]

I was thinking about cutting out the roll cage in my ambo (similar to the OP's pics). It reduces headroom, adds weight and in the end I don't suspect it will do much in the event of a rollover.

 

[Len.Barron]

I was thinking about cutting out the roll cage in my ambo (similar to the OP's pics). It reduces headroom, adds weight and in the end I don't suspect it will do much in the event of a rollover.

Most of those flat topped ambulance hightops will sag out in the middle without some type of support, I agree the way they did it isn't very elegant/efficient but you'll probably regret just eliminating it if you don't do something to replace it.

 

[jblaze5779]

Most of those flat topped ambulance hightops will sag out in the middle without some type of support, I agree the way they did it isn't very elegant/efficient but you'll probably regret just eliminating it if you don't do something to replace it.

I can see your logic but the top never actually touches the roll cage. There is about ~ an inch of space between the steel and the fiberglass across all the rollcage ribs. It's definitely not secured at all to the rollcage.

 

[gmtech]

while cleaning my ambo's roof. I but a knee on it, and it flexed quit a bit it cant be more than 1/2" thick if not more like 1/4". I think the support structure should be left in or like [U]Len.Barron[/U] said do something else to support it.

 

[jblaze5779]

while cleaning my ambo's roof. I but a knee on it, and it flexed quit a bit it cant be more than 1/2" thick if not more like 1/4". I think the support structure should be left in or like [U]Len.Barron[/U] said do something else to support it.

When installing my max fan I had the gf get up and sit on the top to cut the hole. She was alright but I've never attempted to get on top as I know it's probably a bad decision. You could probably add a vertical rib along the length of it to prevent flexing in the wind but you still wouldn't be able to walk on it.