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Calling any engineers...
I'm looking at building a trailer using Aluminium honeycomb panels (alum. honeycomb core, with either alum sheet or fibreglass/epoxy sheet).
Just wanting to know how the numbers stack up against steel for rigidity. Eg: if AHCP has the following properties, what is the equivalent in steel plate/sheet.
Panel thickness 6mm 10mm 15mm 20mm 25mm
Section modulus W (cm2/m) 2.6 4.6 14.0 19.0 24.0
Rigidity E-I (kNcm2/m) 7100 21900 75500 138900 221600
Modulus of Elasticity (N/mm2) 7000 -
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I can't answer your question but am intrigued.
What kind of trailer - small baggage, car transporter, tow-a-van, teardrop camper etc ?
Will it have a separate chassis or will it be a monocoque ?
I suspect the strength of the panels will also relate to the design and therefore a comparison "like with like" of AHCP to steel might be not as simple as initially thought. For example an egg box is strong due to the design shape and not the strength of the cardboard.
Tell us more idc about the material and project as I assume it's the same stuff race cars are built from.
Paul h
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Jul 17, 2013 10:06:46 GMT
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The honeycomb panels will be much more vulnerable to damage than steel, which is not really what you want on a trailer, depending on the usage. Once you break through the thin skin of the panel, then most of the strength is lost.
If you're planning on using it as a floor, then you would probably need to protect it on both sides. If you're using it as a structural member for a monocoque, then you will need to design it extremely carefully. I would assume that this is most probably going to be a camper, because for any load-carrying type of trailer then the durability and low price of steel will make it the hands-down winner.
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Jul 17, 2013 13:27:08 GMT
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It's kind of hard to explain without pictures, but my design is a sort of hybrid trailer. It's like a cage trailer in that it hauls stuff Motorbikes, gear, food etc, but has a lid with a flat folding tent.
The main drawbar and ladder frame would be steel, however the floor, lid and possibly the sides were intended to be AHCP. Using the weight's/sizes available, I can make the frame and drawbars come out to around 68kg. The floor and lid have 9.5m2 surface area, meaning in AHCP they can be as little as 16.2kg.
Add wheels, suspension and stub axles, then I reckon I could get this thing under 130kg unladen.
Reason why I'm looking at doing it this way is, in Queensland (Australia), self-built trailers with an aggregated towing mass of less 750kg don't have to go through ADR (Australian Design Rule) inspections. (Pretty expensive). By making the trailer as light but rigid as possible, it leaves more room for actual holding ability. With about 600kgs to play with, it would leave a lot of room for motorbikes, esky/fridge and food, tent and gear.
Given AHCP is usually used in aircraft floors, superyachts, motorsports, truck/trailer bodies etc, where weight vs strength is critical, I'm hoping it's rigid enough to cope with a couple of hundred kilos (remember it's sitting on a steel ladder frame) whilst being a decent saving compared to steel or hardwood. (Just for reference, 10mm Thick AHCP with fibre/epoxy top and bottom sheets is 1.7kg/m2, whilst 3mm plate steel is around 23kg/m2)
So Engineers, can you help me with the figures?
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mikeymk
Part of things
'85 Polo Coupe S 1.6 16v
Posts: 931
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Jul 17, 2013 13:49:35 GMT
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Horses, you wouldn't believe the damage they can do. They can kick or stamp their way out of a bank safe..
I rebuilt/restored a horse trailer recently, twin axle so it gets some twist unlike single axle trailers (although the largely steel body helps, consisting of angle iron frame and corrugated sheet steel rivetted into place with a sheet fibreglass roof). The frame was a simple one made entirely of said angle iron, L type for the inner framework, and rectangle box section for the outer A frame. The floor was ply chipboard about an inch thick, laying into the angle iron.
If i was gonna make a trailer for a car, i'd probably go with the same design. If for your needs, you could make one on a lighter duty scale.
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Jul 17, 2013 13:50:55 GMT
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That sounds like a really interesting project, but I think it would be better and cheaper to just start with a standard steel trailer and blow the 750kg limit out of the water. Assuming that you achieve a trailer tare weight of 150kg and are taking two dirt bikes at 150-200kg each, that leaves you with 200-300kg for your tent, eskys, fuel, spare tyre and all other gear. If you ever get tempted to squeeze in a third bike then you will be way over weight. If you want a decent mattress in your tent, then that is a fair few kilos just to start with!
If you do want to do it, then you really need a rough design before you can do any deflection calculations. Are you going to use a perimeter frame for the trailer? How many crossmembers at what spacing? Don't forget that if you're going to be sleeping in a roof top tent on the top of this thing, then it will have to have a decent support for the top.
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Most small dirt bikes (250cc)are less than 150kg. EG: the Yamaha WR250F is 118kg Wet. So 3 of those would be 351kg. (Kawasaki and Suzuki DRZ250 are 131kg, so still less than 400kg for 3 of them). I was actually only looking at putting pit bikes in there as campsite runarounds, so it would be lighter again.
If it was about cost, then I wouldn't build anything, certainly not with stuff mainly used in motorsport/aerospace/etc. As someone said; "Lightweight, strong, cheap - Pick any 2"
Drawbars are 2800mm long, with the ladder frame being (LxW)2500mmx1900mm. (This leaves 600mm width for wheels etc, as the max allowable width is 2500mm). the frame is then braced every 625mm or so with a cross bar (2500/4 sections(3 crossbars))
As for the lid, it will be removable. but at this stage, it will be 2500x1900 as well, with a x-brace to help support sleeping peeps. This will drop into the top perimeter of the "cage" (1400 off the ladder) which will have Rectangle/Square corners and angle rim. All this will be double bolted to the frame, with the top perimeter made from 90* angle.
That's the best I can describe it at this stage. When I get home and make the models (rather than just paper sketches) I'll post them for peeps to see.
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edwell
Part of things
Posts: 199
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Jul 18, 2013 10:57:34 GMT
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Have you looked into alucobond or similar? It is an aluminium sandwich with a polythene core, might be better for the sides / top. It is commonly used for siding panels on modern buildings but also for custom trailers and the like, comes in a variety of anodised finishes, and is very easy to work with. Not durable or rigid enough for the floor though. www.transport-industry.com/ti-cars-trucks.html?&no_cache=1&tx_realty_pi1%5Bpointer%5D=13sorry used the quick reply so copy and paste link |
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Have you looked into alucobond or similar? It is an aluminium sandwich with a polythene core, might be better for the sides / top. It is commonly used for siding panels on modern buildings but also for custom trailers and the like, comes in a variety of anodised finishes, and is very easy to work with. Not durable or rigid enough for the floor though. That's a good idea for the sides. It's the Alucore that I was looking at using for the bottom and top, but will probably be more expensive due to the higher amount of aluminium used. |
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drdick
Part of things
Posts: 359
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The figures in your first post are in really odd units but EI for a 3mm steel sheet seems to be 4725 in the same weird units implying that the 6mm AHCP is more rigid (this is a 7am coffee calc. so check it). So whilst it would look good on that measure I'd go with Waveman because those panels are easily damaged, any structural connections you make to the frame or when attaching the walls will destroy the continuity of the AHCP panel making it very weak.
Got a link to the source of the original numbers? I'd like to see especially as E for aluminium is 70000 in the stated units not 7000, maybe a copy and paste error?
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Last Edit: Jul 19, 2013 6:26:24 GMT by drdick
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BiAS
Club Retro Rides Member
Insert witty comment here
Posts: 2,230
Club RR Member Number: 147
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Jul 19, 2013 18:38:11 GMT
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What about an angle frame made of alu with the bits and pieces bolted to it, then use the AHCP to stiffen that. Not that much weight gain for the additional strength?
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(car+wheels)-rideheight=WIN
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Here is the original figures. www.alucobond.com.au/uploads/Alucore%20Downloads/ALUCORE_Product%20information_2010_lowres.pdfI've sort of scrapped the idea of using ACHP. They're hard to get a hold of for a decent price (AU$440 per sheet x6!!), and 2 plies of 0.5 aluminium sheet would have nearly the same strength that I need. I'll still be using as many lightweight materials as possible, but see the sense of using regular, off the shelf available parts, rather than full on custom stuff... Why do I have to design expensively? |
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