trailer wieght for an ultra light build

[MidTNJasonF]

I have decided on 5'X8' for my build but I need to keep the weight way down. I am stuck for the time being with a class 1 hitch (2000lb, 200lb tongue weight) and my tow vehicle is a Mazda 5. The Mazda 5 is not rated to tow in the US but the identical vehicle is rated at about 1350lbs in Europe. I would like to keep total weight to 1200lbs.

My build will be a toy hauler for my race bike and occasionally one of my street bikes. The motorcycles weigh approx 300 lbs. to 500 lbs. wet depending on which bike I take leaving me with a trailer weight capacity of 700 lbs. to 900 lbs. It will be a bare bones foamy build without water or significant power of any sort. Probably a battery, a couple LED's, a cooler, and a water jug on a shelf will be my only amenities.

I am on the fence for trailer and material selection.

Northern Tool has their steel 5'x8' listed at 265 lbs. http://www.northerntool.com/shop/tools/product_200356494_200356494
They also list an aluminum 5'x8' at 215 lbs. which saves me 50 lbs. at nearly 2.5 times the cost.[url]http://www.northerntool.com/shop/tools/product_200578601_200578601
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The Northern Tool steel 5'x8' looks very similar to the Harbor Freight 4'x8' heavy duty trailer but I would be forced to build out over the frame 6" per side and would have to incorporate the wheel arches into my design limiting the interior. I would assume its weight to be just under the Northern Tool 5'x

So if I want to go with Aluminum and 5'x8' I can spend $1300 or I can build something. The trailer design I have in mind would be 60 linear feet of square or rectangular tube. Not knowing the strength properties of aluminum vs. steel square tube I am unsure what wall thickness I would use if I sub aluminum for steel.

I worked up the chart below to compare weights and costs of the various options.



It may be tough to see due to size I guess. The important things are in the bottom two charts. If I can stick with 1/8" wall 2"x2" 6061 square tube I can build the frame for $262.59 and it will be about 67.5 lbs. Now that is just the frame itself including the axle, wheels, hubs, coupler, and lights. All of those items will add weight and cost. In comparison the same dimension and wall thickness steel tube would come in at $247.67 and 183 lbs. So a significant weight penalty for a very small cost savings.

Since a sheet of 1/2" ply is close to 50lbs and a sheet of 3/4 is close to 75 lbs that will add to the trailer as well since I will be counting on my decking to provide some rigidity. That puts me up to 117.5 lbs. for 1/2" and 142.5 lbs. for 3/4" decking on the trailer before axle, wheels, and other items. I still need to select those items and find some weights.

The question is can I use 0.125" wall aluminum tube or will I have to go to a thicker wall? 3/16" wall is not a huge weight penelty at 98.4 lbs. for the structure but is adds more than a $100 in the cost of materials. 2.5"x2.5" 1/8" wall would be a compromise between the two.

I have even considered Aluminum C channel as RandyG http://www.tnttt.com/viewtopic.php?f=50&t=54126 is using but I fear it may not be strong enough when for hauling the motorcycles. It would probably be fine for the light static load of the structure and camping equipment that would be in it but not for a 500lb motorcycle.

[pchast]

Interesting question...

If you will only ever have one bike in the trailer why not only worry about the tray structure you place it in?
The rest of your floor need not be as heavy or strong.

[MidTNJasonF]

Well I would have reinforcement under the front wheel Chock and under the tie down points that will be recessed into the floor. One concern I have is I may need to place the bike slightly off center. I want just a bit of shelf and a recess on the right side which would shift the bike 6 to 8 inches off centerline.

I basically need 3 feet in width for the bikes. My current plan has a 16" intrusion in the the right side out of my 5 feet. The closest my bikes centerline can be to the right edge is 34 inches. With 2" walls my centerline will be 28 Inches. Not huge but I want a strong trailer to support the off center load. What weight will be in the trailer other than the bike will be down the right side to help balance that out.

I due plan on adding gussets in the corners of the frame structure as well.

[MidTNJasonF]

uploaded a couple shots of my proposed design for the trailer.

[alaska teardrop]

Jason, I think the .125"x2x2 aluminum tube is fine for your floor platform depending on what axle you use & how it is mounted. Offhand I'd say that the 1/8"x2x2 steel tube is OK for the three tongue pieces, but that the 1/8"x2x2 or 3/16"x2x2 aluminum tube would not be adequate for a 1200# trailer.

By considering the trailer weight & tongue length, the correct tongue strength of various sizes & shapes can be determined. See here: viewtopic.php?f=35&t=56880

[MidTNJasonF]

Jason, I think the .125"x2x2 aluminum tube is fine for your floor platform depending on what axle you use & how it is mounted. Offhand I'd say that the 1/8"x2x2 steel tube is OK for the three tongue pieces, but that the 1/8"x2x2 or 3/16"x2x2 aluminum tube would not be adequate for a 1200# trailer.

By considering the trailer weight & tongue length, the correct tongue strength of various sizes & shapes can be determined. See here: viewtopic.php?f=35&t=56880

I had hoped to keep it all aluminum. I prefer to have it welded and would especially like to avoid a bolt on tongue scenario. I will have to do some research on the stress and yield properties of Aluminum tube compared to steel and see if a larger section size and/or thicker wall aluminum tube could be subbed in for the steel.

Thanks for the links. Looks like my proposed Composite design is a good but not ideal choice. I had planned on a 4' length of tongue forward of the frame. I could change that to an A frame design and gain significant strength and reduce the overall length of tube I would need. I will have to source a different coupler but that should be easy enough.

I plan on using these Reliable Rubber Torsion Axles http://www.northerntool.com/shop/tools/product_200335742_200335742 1000 lb capacity per stub for a combined capacity of 2000 lb. I planned on bolting them directly to the frame at a cross beam location with extra gussets at that location. I may even throw a 1/4" plate on as a gusset and to spread the load in that location if I feel it is needed once I have all the parts in hand.

I plan on hubs like these depending on what bolt pattern I need. http://www.northerntool.com/shop/tools/product_200442391_200442391?utm_campaign=bazaarvoice&utm_medium=Default&utm_source=AskAndAnswer&utm_content=Default

[MidTNJasonF]

Thinking out loud here but...

Going with 2"x2" .125 wall Aluminum for the deck, changing to an A frame design, and making the tongue A frame from 2"x2" .250 wall will only increase weight and cost slightly. There should be no problem welding the 1/4" wall to the 1/8" wall tube.

One problem I see is there appear to be no bolt on A frame couplers. All I seem to find are weld on couplers other than one very expensive 15k coupler for a 2 5/16" ball. Way more than I need. I may have to drill the coupler and mount it with two grade 8 bolts per side. 4 bolts of either 3/8" or 1/2" should have more than enough shear strength for the application.

A513 Hot Rolled as a Yield strength of 72,000 PSI, 6061 Al has a Yield strength of 40,000 PSI. I am thinking that going to 1/4" wall doubles the strength of the tube and hopefully doubles the Yield Strength as well. It may very well not be a linear relationship though.

[dwgriff1]

With all of that I am not sure the "ultra light" moniker fits. Might not even be lightweight by the time you are finished.

dave

[MidTNJasonF]

With all of that I am not sure the "ultra light" moniker fits. Might not even be lightweight by the time you are finished.

dave

From Coupler to tires including lights and a 3/4" ply deck the weight comes to 327 lbs. The previously mentioned all aluminum Northern Tool Trailer is 308 lbs with a 3/4" ply deck on it. That is the lightest 5'X8' trailer I can find specs on so far. Not far off from my total weight and I figured 14" wheels and a beefier frame.

That leaves me with about 375lbs for the structure north of the trailer frame. That should be fairly simple and allow me to come in under my 1200lb target goal.

Ultra light is a mater of perspective. For toy haulers it will be very light. When compared to a flat deck utility trailer with limited weight capacity it does not seem all that light.

[angib]

Sadly, you can't just compare the strength of steel and aluminium to work out equivalent thicknesses. Aluminium has a much lower point at which it will start to crack with repeated use (the "fatigue limit") compared to steel, so you need a bigger margin on aluminium, unless you say that the trailer isn't going to get used much and accept the shorter lifespan.

If you design an aluminium trailer to last as long as a steel trailer, it won't be much lighter.

[rowerwet]

if you want light weight, go with a foamie, till you get the bike(s) on the trailer and the bare weight of the trailer frame you've got a lot of weight to stop and go with on a small car.
I tow my TD with my 4 cyl Focus, I figure I'm around 1200 lbs with all my gear, towing at the 2000 lb limit for the focus in the rest of the world would not make for an easy drive and be very hard on the car.

[MidTNJasonF]

if you want light weight, go with a foamie, till you get the bike(s) on the trailer and the bare weight of the trailer frame you've got a lot of weight to stop and go with on a small car.
I tow my TD with my 4 cyl Focus, I figure I'm around 1200 lbs with all my gear, towing at the 2000 lb limit for the focus in the rest of the world would not make for an easy drive and be very hard on the car.

As I stated in my first post this will be a bare bones foam build. I am just trying to work out a way to get the base trailer as light as possible as well. There will be no plumbing and minimal 12v electric for a few LED lights. The only wood structure will be around the window, side door, and the rear door. I need some structure around the rear ramp door to support it since it needs to be strong enough to handle the weight of the bikes.

[KCStudly]

It looks like you are taking a very analytical approach, and I second that as a good approach.

Here are some random thoughts; just my $.02:
Save 60-80 lbs plus wiring weight and save all of the trouble of wiring light switches, etc. by using self contained battery operated puck lights supplemented by a headband lamp. For more area lighting, use a Coleman lantern; they burn a long time and give off a lot of useable light.

The front diagonal braces in your frame are redundant to the tongue A-frame, unless you need them for tie down anchor points.

You only plan on taking one bike at a time? What about your pit support gear (tool boxes, lever jacks, spare wheels/tires, tie down straps/brackets, fuel/oil/cleaning supplies, etc.)? You can't use the weight of the lighter bike to set your margin if you are still planning to haul the heavier bike, so subtract all of your cargo weight from that 700 lbs.

I would seriously consider looking at Angib's ultra light A-frame design with the heavier 3/4 ply floor and a perimeter of 1x or 2x cedar to stiffen the edges. I'm confident that you could build a very suitable foamie bike hauler using a lot less frame than you have drawn. Use the A-frame as the main front tie down anchor and stack your gear shelves in the front corners so that you can load along the centerline.

To go truly light, all you have to do is sharpen the pencil!

Anyway, welcome to the forum, and I look forward to following along on your project!

[rowerwet]

if you want light weight, go with a foamie, till you get the bike(s) on the trailer and the bare weight of the trailer frame you've got a lot of weight to stop and go with on a small car.
I tow my TD with my 4 cyl Focus, I figure I'm around 1200 lbs with all my gear, towing at the 2000 lb limit for the focus in the rest of the world would not make for an easy drive and be very hard on the car.

As I stated in my first post this will be a bare bones foam build. I am just trying to work out a way to get the base trailer as light as possible as well. There will be no plumbing and minimal 12v electric for a few LED lights. The only wood structure will be around the window, side door, and the rear door. I need some structure around the rear ramp door to support it since it needs to be strong enough to handle the weight of the bikes.

sorry missed that somehow...
would a single plank type ramp be lighter than the whole door being reinforced? then the door could hinge up to make an awning, made of foam it would be super lightweight. the plank could store under the trailer floor.

[MidTNJasonF]

It looks like you are taking a very analytical approach, and I second that as a good approach.

Here are some random thoughts; just my $.02:
Save 60-80 lbs plus wiring weight and save all of the trouble of wiring light switches, etc. by using self contained battery operated puck lights supplemented by a headband lamp. For more area lighting, use a Coleman lantern; they burn a long time and give off a lot of useable light.

The front diagonal braces in your frame are redundant to the tongue A-frame, unless you need them for tie down anchor points.

You only plan on taking one bike at a time? What about your pit support gear (tool boxes, lever jacks, spare wheels/tires, tie down straps/brackets, fuel/oil/cleaning supplies, etc.)? You can't use the weight of the lighter bike to set your margin if you are still planning to haul the heavier bike, so subtract all of your cargo weight from that 700 lbs.

I would seriously consider looking at Angib's ultra light A-frame design with the heavier 3/4 ply floor and a perimeter of 1x or 2x cedar to stiffen the edges. I'm confident that you could build a very suitable foamie bike hauler using a lot less frame than you have drawn. Use the A-frame as the main front tie down anchor and stack your gear shelves in the front corners so that you can load along the centerline.

To go truly light, all you have to do is sharpen the pencil!

Anyway, welcome to the forum, and I look forward to following along on your project!

I am a former Machinist, Quality Control Technician, Internal Auditor, and now Quality Assurance Manager with one degree in Mechanical Engineering and one in Machine Tool Technology. Over analyzing things is my forte. I am actually suffering from analysis paralysis at the moment and I need to break that cycle. I am actually going to look at a pre built trailer tomorrow that I may be able to pick up for a song. I want this done quick so a custom built trailer frame may have to come with build number 2.

Yes only one bike at a time and mostly the smaller of the bikes. My only heavy bike is my street bike and I normally just ride that. I am a light packer and camper. I have been camping off the bike with just a couple of 35l side cases and a 45l top case for years. I will only occasionally take the street bike when I want to base camp for a few days and explore an area. The race bikes are lighter and need very little support. I do not travel with spare wheels or tires, all the tools I need can fit in a typical hand carry tool box, I do not need a full chest, I do not need a generator to power tire warmers, and 1 5 gallon jug of fuel will get me through a couple practice sessions and a race. I might need two 5 gallon jugs but that is easy enough. Racing vintage bikes is fun and uncomplicated. I would have to factor in the weight of my 10x10 pop up canopy I take with me for the pits and a couple folding chairs.

I found a link http://www.angib.pwp.blueyonder.co.uk/teardrop/tear31.htm on the Angib trailer and I do like the design but I would be concerned that it would not have the support I need to haul the bike. I think I would have to reinforce it a good bit at the wheel chock and tie down points. Maybe up the center as well where the bike would rest/sit.