How much frame does a standy need?

[angib]

Someone on the Fiberglass RV forum sketched out the frame to their 1970s Perris Pacer - another one of the 13ft fiberglass trailers based on the Boler, such as the Scamp still made today.



The Perris was slightly different as it had a complete bottom moulding including its floor, shaped like a bath tub. So that must have provided it with some body strength, though the door opening cuts away all of one side of it.

Now I've modelled and drawn this frame out because it helps show how little frame a trailer really needs. The (red) 3"x1-1/2" rectangular tube used for the A-frame and main rails is pretty sensible (10% heavier than a 2"x2" but 50% stronger vertically) but check out that 2"x1" (green) channel that replaces the main rail under the door opening!! That is a very small section, in a weak orientation. I can't think why they didn't at least use the same 2"x1" (purple) rectangular tube that runs across the trailer supporting the dropped floor.





In case it looks confusing - yes, they did mount the axle with its arms leading, not trailing. And there really are just two (blue) cross-members, both 3"x1" angle - the back one is mounted in its weak orientation (3" leg horizontal) as I think the dinette table pedestal bolts through it.

If you want you can download a PDF with greater resolution here: http://teardrops.us/userfiles/53/perris-pacer-chassis-2.pdf

Now this trailer probably weighed 1000-1500lb - they were pretty basic back then - and several have survived the 30 years since then, so we have to conclude that this is all the frame that's needed.

To be fair, the subject of the Perris Pacer did turn up because of a crack on the frame - amazingly to me, the crack wasn't in that little channel under the door, but was at the joint between the left side rail and A-frame, where the weld had cracked - presumably after 30 years of fatigue.

Food for thought?

Andrew

[brian_bp]

Thanks for the illustration, Andrew.

As already mentioned, the Perris Pacer is one of the descendants of the classic Boler 1300, and even the frame is similar. The drop under the doorway is a common feature of these as-low-as-possible designs, but the Boler used a wider sheet metal fabrication instead... it's still a weak point, perhaps, but the Boler 1300 frame usually fails near the joint that went on this Pacer... in the Boler it's a poorly bent section of square steel tube. Some people have reinforced under the door and dinette section, but the rest of the frame seems quite adequate for the task.

I agree that the channel under the door would be stronger as a box section, but what's the wall thickness of the channel? It's such a short piece that a very heavy section could be used without unreasonable weight. This reminds me of the section of many hitches for cars and small SUVs, which have a section of solid rectangular bar (instead of the square tubing of the rest of the hitch crossmember) to get around an exhaust pipe; it's far from optimal, but works in a short and thick enough piece.

The repair described in the FiberglassRV topic looks (in the posted photo in that thread) like a rectangular plate bent over the joint and welded around the full perimeter. It could have been better shaped, but seems like a decent solution... much better than one of the commenters in that topic suggests.

The leading arm configuration was selected to allow the axle to mount to the stepped-up section of frame, for the lowest possible ride height. The arms are always angled up, along the same theme. Ironically, today most owners who change anything about the suspension jack them substantially higher, often adding material to space the axle brackets down. If they're going to do that, it seems to me that they should modify the frame to take advantage of the higher stance to provide a more robust door step area, and to actually suit it to the suspension. Of course, that would require understanding their needs, and the logic beind the original design.

[aggie79]

Can you say why these small standies have a drop frame at the door? I assume that it is to keep the bottom of the door near the floor level to keep from having to step over a higher threshold.

When I first came across this website, I saw the Raven/Argonette profile and can't get that design out of my head. However, my first build, starting in about two weeks when the last of the parts come in, will be a teardrop.

This information is very helpful.

[Mini Renegade]

Hey Andrew, if the suspension units are `backwards` will they still work ok? I have been toying with the idea of turning mine around to move the wheels forward to reduce nose weight but thought it might bounce too much, any ideas??

[angib]

Can you say why these small standies have a drop frame at the door? I assume that it is to keep the bottom of the door near the floor level to keep from having to step over a higher threshold.

Quite right. In an attempt to explain how it works, I've added a tinted glass floor and a dotted line doorframe to this illustration. You can see how the floor lies inside and below the main frame rails, but steps up to miss the axle and comes out to the doorway through the dropped frame rail. I hope.



This also shows that if the axle were the normal way round, but the wheels were in the same place, the axle tube would run through the middle of the walking area!

Andrew

[angib]

Hey Andrew, if the suspension units are `backwards` will they still work ok?

This is only acceptable is the suspension has an 'Up' start angle - so that the wheel spindle is above the axle tube.

As you're in the UK and I presume you're talking about normal UK torsion axles, you will have a 'Down' start angle of 20-30 degrees and trying to run that sort of axle reversed would be bad - you would have little suspension movement on big bumps. I can give the explanation but be warned, it's long and technical!

Just to clear up any confusion for Merkan readers, standard torsion axles in Yurp are not available with a choice of start angles: you get the manufacturer's standard angle and that's it - unless you want to place an order a few hundred....

Andrew

[Mini Renegade]

Hey Andrew, if the suspension units are `backwards` will they still work ok?

This is only acceptable is the suspension has an 'Up' start angle - so that the wheel spindle is above the axle tube.

As you're in the UK and I presume you're talking about normal UK torsion axles, you will have a 'Down' start angle of 20-30 degrees and trying to run that sort of axle reversed would be bad - you would have little suspension movement on big bumps. I can give the explanation but be warned, it's long and technical!

Just to clear up any confusion for Merkan readers, standard torsion axles in Yurp are not available with a choice of start angles: you get the manufacturer's standard angle and that's it - unless you want to place an order a few hundred....
Andrew

Cheers Andrew thats what I thought as well, just wanted an expert oppinion.