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Old 12-08-2014, 10:41 AM   #11 (permalink)
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Ecky,

I use PowerPoint 2010 to do my overlays, put both pictures on one slide and drag the AST-II over the picture of the car. The AST-II will go semitransparent and you can see them overlaid quite nicely. Use the built in scale and rotate tools to make them match up.
Your car is already fairly boat-tailed in the back, making a trailer that continues the boat tail to reduce drag will result in a fairly small trailer.

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Old 12-08-2014, 01:12 PM   #12 (permalink)
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How is the quality of harbor freight's trailers? A lot of reviewers have given them good ratings but mention that they watch for the hubs getting hot. If I can make something for not too much more that has better suspension, is less likely to rust away quickly, and doesn't have crap bearings, etc. I would prefer that, but I'm giving consideration to spending $180-230 on one of those as a base and building on it. Working on some drawings based on one of those right now.
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Old 12-08-2014, 01:16 PM   #13 (permalink)
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I once made a trailer axle from a piece of 2" EMT (thin wall electrical conduit) by welding in a pair of front wheel spindles from the junkyard. I mounted the axle solid to the trailer frame. No springs, no suspension.

The trailer towed well on the highway without bouncing. I stress tested it with an estimated 1500 pounds of sand and concrete blocks. No problem. Another stress test filled it with firewood and pulled through a field watching the firewood bounce out. No problem.

I sold after several years. I ran into a friend of the new owner about 20 years later, and he said the trailer was still in use.
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Old 12-08-2014, 02:00 PM   #14 (permalink)
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Harbor Freight

*My trailer from the 1980s is essentially what Harbor Freight sells today.
*They go on sale regularly so you might get a price break there.
*I made a plywood flatbed,then created a top.
*The top is 1/2-" EMT,bent with an EMT bender and gas welded into a space frame,covered with 1/8" Lauan plywood/fiberglass,and cast fiberglass radii,laid up inside split PVC pipe 'molds.'
*The wheels were 13" from a CRX,reversed.(I had to grind the wheel centers to fit over the hubs.
*All-Season radials from Discount tire were okay for my light loads (1/4-ton max)
*As pulled,with no belly or gap-fillers I lost 2-mpg @ 55-mph (50-mpg) Denton-to-Los Angeles round trip.
*If you're spooked by the Chinese wheel bearings,you could pop in Timken or another brand.Just set enough 'slop' in the preload and use nothing but wheel bearing grease.


This is a study I did for your car.It is excessively long, enough for camping.As with BamZipPow's 1-wheeler,the idea was to get the streamlining good enough that you'd 'gain' mpg while pulling it.
Another:

This profile would be okay for plan taper
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Last edited by aerohead; 12-08-2014 at 02:02 PM.. Reason: spelling
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Old 12-08-2014, 02:26 PM   #15 (permalink)
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Much appreciated!

Here's a sketch I've made of HF's trailer with 12" wheels, as it had more complete data than the 8" version. There's still some missing data so I had to extrapolate some of the measurements.




From the front of the platform, I'd have about 33" to the bumper, which would almost allow 90° turns.

In the interests of keeping tongue weight down I would like to keep most of the weight approximately over the axle, which may necessitate moving it forward given the taper, or perhaps extending the trailer back another ~24 inches, giving a total usable area of around 40" x 72". The front looks like it should be roughly 15" above the platform which doesn't leave a lot of room for taper, but if I need to haul more I could always leave the cover off. If I extended the box forward another 12 inches it would allow for a depth of approximately 19-21" but I'd be eating into my turning radius.

What do you guys think?

~~

One thing I'm confused about:

Heavy Duty Utility Trailer - 870 Lb. Capacity
40-1/2" x 48" Small Utility Trailer - 1090 Lb. Cargo Capacity

^According to the overview, both of those trailers have the same height despite one having 8" wheels and the other having 12" wheels, but I'm skeptical. Would the trailer with the smaller wheels really have the same deck height?
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Old 12-08-2014, 05:36 PM   #16 (permalink)
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They would have the same deck height at the hitch but not at the wheels.
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Old 12-08-2014, 11:42 PM   #17 (permalink)
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Quote:
What am I doing wrong here?
This is IMHO only, as you will probably have your trailer on the road before I have mine.

I suggest that it's the next step you need to look at, The trailer box 50% outside The Template in both the top and plan view. You could put a little template on the trailer box.



Personally, I like this one. You could take a size-graduated set of inner tubes, string they on a bungee between the trailer and car and then inflate them. Match the body color with Plastidip S.

Or make it like a bouncy castle.

It would like like a caterpillar or the larval stage of a flying car.
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Old 12-09-2014, 07:03 AM   #18 (permalink)
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I think you have two main options. One is to make a small trailer that continues to follow the template off of the car which may actually help MPG, but has limited inside space and usability. The second, as Freebeard mentioned, is to make a larger trailer which will have more space and usability, but may actually slightly hurt MPG.

It is all about your intended use. If you are planning on dragging this thing around all the time, I would suggest option 1. If this is just an occasional use trailer for specific hauling needs, I would suggest option two.

For an option 1 trailer, I think you will need to use some sort of gap fillers to get to a net positive effect. Freebeard has some ideas above, and you can also look at Aerohead’s pictures and BamZipPow’s trailer. I would also be wary of using a harbor freight trailer axle for a 100% follow behind the car everywhere trailer, depending on how much you drive it may not be designed for that much use. I think the swivel wheel trailer as BamZipPow is using is the best idea for this sort of trailer, as it simplifies the gap fillers and would maximize interior space and since you wouldn’t have to worry about turning radius, but you would need to be cautions of your new tail sticking out the back.

For an option two trailer, I would build something like the white trailer Aerohead posted. Make it 48”+ between the wheelwells to maximize utility. Even if you lost 2MPG pulling it, you would still be lightyears ahead of anything else that could haul that much stock. Only use it when you need it.

Lastly, don’t forget safety. Your car probably would be able to have a class 1 or 2 hitch at the most, using a 1.25” receiver. Make sure your trailer will not exceed the recommended capacity of the car or hitch. If the weight of the trailer is going to be significant compared to the weight of the car, I wouldn’t attempt this without trailer brakes. I know that you know all of this, just keep it in mind.
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Old 12-09-2014, 03:33 PM   #19 (permalink)
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axle width/deck height (leveling)/wheel diameter

I wanted to mention that the smaller trailer has a C-Channel axle,with stub-axle hubs captured by clamps.
Narrowing the axle would be straight forward if you chose to do that.
The frame members would have to be re-drilled for the new width,depending upon how much you shrunk the dimensions.
It would allow some flexibility with respect to the axle location.
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I suppose that the receiver tow bar could be customized for a proper vertical ball position to keep the deck level.
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The 12" wheels should have a rolling resistance advantage over the 8".If you can get the 14"s on there,it would really slow down the wheel bearings.
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Old 12-09-2014, 04:40 PM   #20 (permalink)
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Thanks for the tips. My intended uses for this trailer will be mixed, though at a later date I may choose to go with two different ones for different uses, or detachable tops to go on the platform. Aero box for trips, open top or rack for plywood/lumber.

Next summer I'm moving a load of stuff from Florida to Vermont, and a 40x48" trailer should be just about right for what I need. If a Harbor Freight trailer won't survive a 24 hour drive, it's of no use to me. After that, I'm probably going to do a tour of the country before heading to Asia for a year or two. I may or may not use the trailer for this. When I get back, the trailer will be likely be used mostly for bringing extra cargo along on trips, as well as hauling things around town that will not fit in the hatch.

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