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PostPosted: March 28, 2011, 1:19 pm 
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It's hard to choose where this one should go. I consider a trailer to be a necessary item for a Locost, both for transport of materials necessary to the construction of the Locost, and for transport of the actual automobile afterward.

I'm not building a big 16-20 foot trailer, but something more manageable at a 10-12 foot deck plus tongue length. I'm trying to decide on the wall thickness for the tube. I see lots of utility trailers made of angle steel but that doesn't seem safe enough or strong enough to me, so fully boxed steel it is. I'm looking at 2x3 tube, but what thickness? 0.083? 0.012? 0.1875? 0.25? A little two-seater shouldn't weigh much. Certainly less than my 3600lb Jeep. Although, how is it a 2011 Camaro weighs more than my Grand Cherokee? That is a lot of fat. I would think that 2400 pounds would be more realistic, even for a V8 Locost.

I'm thinking 2"x3"x0.1875" frame with a 2.5"x2.5"x0.25" tube down the centerline and a 3500# axle. Am I off base, or would that be adequate strength?

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PostPosted: March 28, 2011, 2:34 pm 
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Not sure on the tube weight, but a Locost should weigh somewhere between 1200 and 1600 lbs. A 2400lbs Locost would have to be made of lead!


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PostPosted: March 28, 2011, 2:53 pm 
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You can keep unladen weight and ground clearance pretty low using one of these http://www.dexteraxle.com/torflex_axles you can also get them without a beam from, ummm, I disremember where but they exist..
Personally I prefer 2x4 square tube just because it looks right to my eye, its been a while but I think we used .095 wall when I worked at Millerick. I know I used some scrap for bumpers on my truck, worked well for that.
I still find it hard to believe I was pulling around 3 tons of stuff with a Chevy Luv but. ..
:cheers:

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PostPosted: March 28, 2011, 4:26 pm 
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Those sizes of tubing are more than enough, as long as you design in strength. I would use the 2x3 for any cross bed braces where a spring shackle will be and at the front where your tongue triangle hits the main bed and at the rear where loading ramps will attach.

One of the biggest problems with using angle iron as structural is that it doesn't prevent twist in the frame. I'm sure you've all seen this twisting motion when those light duty trailers go over bumps. Only a box frame, (made out of rectangular, square tubing, or two angle irons welded into a box shape, will prevent this twisting. I know, I have 9 or 10 trailers.

Tom

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PostPosted: March 29, 2011, 8:42 am 
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I built my trailer from 2x2x1/8 steel tubing and 3/18 aluminum checker plate. I had the aluminum bent into a U shape that adds strength. Really simple design.
Not having springs may seem strange but it allows me to get the trailer as low as possible. When I put my car on it, I only tie down the wheels. That lets the car suspension move and absorb the bumps. Towing it empty is pretty wild. It bounces all over the place.

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PM me your direct email address if you'd like a copy of the plans.
The zip file is too big to send by PM.


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PostPosted: April 8, 2011, 3:54 pm 
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Location: CR, Iowa
Circle Track magazine had a pair of articles on building a low cost car trailer here and here.
If you are looking for plans you can get those from here.
For a low rider trailer a set of torsion axles with electric brakes would be great.


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PostPosted: July 20, 2014, 5:15 pm 
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this has been running through my mind as well, i can tow my car hauler with my astro but it is still a little large for my car.

i think that adding brakes, while nice adds to the weight of the trailer, also adding the second axle will add to the weight of the trailer.

i don't think that the idea of no suspension is worth considering though.

a tilting bed can be done easier with a single axle and a double acting ram or a winch to move the bed, however a tilting bed can be done with the vehicle weight.

alternatively you could just have a trailer hitch jack between the draw bar and the deck to tilt it up and down.

you could try just balancing the deck pivot to the tilt position with a set of lock pins to keep it in place when no weight was on the trailer and a winch to pull it up when not loaded, when the car drives on, the car weight will be enough to tilt it up to the tow position and back down again for unloading.

the pivot point is somewhat critical though as you don't want it tilting up when the car is half way on or off in that the back wheels need to be on the trailer before equilibrium is over reached which means that the deck behind the axle must equate to the wheel base of the car, this is not practical and a system to hold the deck tilted will need to be employed, the question is how do you unlock the holding mechanism when the weight of the car is forward of the pivot.

another method to consider if using a tortional system may be to rotate the axle so that the tortion arm can rotate to a point where the rear of the trailer is on the ground, this could be done with a double acting ram or a single acting ram and gravity, even a winch pulling on a lever to rotate the axle to the towed position, lock pins would need to be provided to keep the axle in place when being towed.

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PostPosted: July 21, 2014, 2:17 am 
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Thumper wrote:
I built my trailer from 2x2x1/8 steel tubing and 3/18 aluminum checker plate. I had the aluminum bent into a U shape that adds strength. Really simple design.
Not having springs may seem strange but it allows me to get the trailer as low as possible. When I put my car on it, I only tie down the wheels. That lets the car suspension move and absorb the bumps. Towing it empty is pretty wild. It bounces all over the place.

PM me your direct email address if you'd like a copy of the plans.
The zip file is too big to send by PM.


Oh well done Thumper, almost all trailers are way overbuilt and this is a genuine alternative.

Tying down by the wheels only is the key as you know, maybe some larger section offroad tyres with lowered pressures might might help the unladen traveling?

I'll take a set of you plans if possible, cheapracer@yahoo.com , thanks!


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PostPosted: July 21, 2014, 10:13 am 
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I've always towed my Formula Fords on a simple home made ( not by me ) trailer with a single axle and no suspension.

I think using ramps are easier than trying to make the trailer tilt. I don't object to the idea of suspension, but you are towing a car which already has a suspension so it doesn't appear high on the list of needs for me. The issue explained to me for a race car is that having a suspension on your trailer saves wear and tear on your rod ends.

The construction on my trailer is a little heavier than Thumper's, it uses steel channel for the wheel tracks for example. I think it is wise to try to strengthen these style trailers a bit by building up the sides with an upper rail. it can just run from the top of the fender down to the ends, sort of a low triangle.

It's a big help with these trailers that they can be moved by hand, even when loaded if you need. So that makes single axle important. This trailer uses ramps instead of tilting. That seems simpler and safer. The ramps just store next to the car tracks on the trailer and connect to them with a simple piece of 1/2" steel rod. I drive the car on and off the trailer, that's on a car with an F3 clutch geared for about 70 MPH in 1st.

I don't use the actual tires to strap down, I tie down to the suspension arms/joints/uprights next to the tire. There is less of a concern here with road tires than slicks which sometimes may not hold pressure well or could have developed a small leak during the day.

The first tow vehicle was a Ford Fiesta, more than a little marginal for the job. That tow car weighed about 1700 and used basically the same engine as the formula car. So extra spare parts, I figured. Later I towed with a Mustang and that was much better.

Single axle, no suspension, no brakes, no tilting. If you need more than this, it's time for an enclosed trailer that also functions as a garage and portable shelter for you and car.

I'm tempted to build one out of aluminum square tubing. It turns out 2"x2"x.25" 6061 is a cheap size to buy...

Go as simple as possible, you can upgrade someday when you need. It's decades later for me and upgrading never got anywhere near the top of my lists of needs. If it works and works well, you go on to other problems. It never hurt anything to drive it thru the rain, but it was a little painful sometimes. Mind you, I drove it in the rain at the events anyway...

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PostPosted: July 21, 2014, 10:15 am 
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I think .125" for steel is plenty on our trailers... Just like our cars don't just go for section thickness, larger sections or trusses/beams are the way to go.'

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PostPosted: July 21, 2014, 11:04 am 
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Just a little bit of engineering here.
Assuming
2x3 .125 wall box section steel tube
144 inch single beam length
1500 pound load ( a little heavy for a typical Locost)

A single 2x3 box beam would support a Locost with a maximum deflection of 2.2 inches and a maximum stress of a tad over 55kpsi, well below it's yield.

A similar 2x3 with only .065 wall would deflect a little less than 3 1/2 inches at a max stress a tad over 87kpsi, still well below it's yield
That's 1 steel beam supporting a car with reasonable deflection over a 12 foot span.
Now consider 2 side beams plus a center backbone. Yes, the trailer will flex a bit, about 1 inch, but the max stress drops to 29kpsi. This ultralight would handle a lifetime of hauling one of our cars without a fatigue failure.

Add a top rail or low triangle like horizenjob mentions and you've got a simple truss than deflects < 1/4 inch.

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PostPosted: July 21, 2014, 11:46 am 
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Don't forget the added stiffness that the U shaped aluminum track give.

TooBusy wrote:
Just a little bit of engineering here.
Assuming
2x3 .125 wall box section steel tube
144 inch single beam length
1500 pound load ( a little heavy for a typical Locost)

A single 2x3 box beam would support a Locost with a maximum deflection of 2.2 inches and a maximum stress of a tad over 55kpsi, well below it's yield.

A similar 2x3 with only .065 wall would deflect a little less than 3 1/2 inches at a max stress a tad over 87kpsi, still well below it's yield
That's 1 steel beam supporting a car with reasonable deflection over a 12 foot span.
Now consider 2 side beams plus a center backbone. Yes, the trailer will flex a bit, about 1 inch, but the max stress drops to 29kpsi. This ultralight would handle a lifetime of hauling one of our cars without a fatigue failure.

Add a top rail or low triangle like horizenjob mentions and you've got a simple truss than deflects < 1/4 inch.


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PostPosted: July 21, 2014, 1:16 pm 
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Thumper wrote:
Don't forget the added stiffness that the U shaped aluminum track give.

TooBusy wrote:
Just a little bit of engineering here.
Assuming
2x3 .125 wall box section steel tube
144 inch single beam length
1500 pound load ( a little heavy for a typical Locost)

A single 2x3 box beam would support a Locost with a maximum deflection of 2.2 inches and a maximum stress of a tad over 55kpsi, well below it's yield.

A similar 2x3 with only .065 wall would deflect a little less than 3 1/2 inches at a max stress a tad over 87kpsi, still well below it's yield
That's 1 steel beam supporting a car with reasonable deflection over a 12 foot span.
Now consider 2 side beams plus a center backbone. Yes, the trailer will flex a bit, about 1 inch, but the max stress drops to 29kpsi. This ultralight would handle a lifetime of hauling one of our cars without a fatigue failure.

Add a top rail or low triangle like horizenjob mentions and you've got a simple truss than deflects < 1/4 inch.


Yep, the C channel adds stiffness as well. I left it out of my rough estimate because of the 120 angle instead of a true "C" and I didn't know how you had it attached.
Your design is more than adequate for our little cars. Nice job sir!

oh, and thanks for the plans. This is on my to do list. :cheers:

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http://www.locostusa.com/forums/viewtopic.php?f=35&t=17496

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http://www.locostusa.com/forums/viewtopic.php?f=35&t=15216


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PostPosted: July 21, 2014, 6:26 pm 
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Location: Halifax, Nova Scotia
As a point of reference my boat trailer is 2x3 tube and was built in 1969. There are no signs of fatigue cracking, but boy, is it EVER flexible. Now, it's much longer than a Locost trailer would be, so the deflections are amplified. (The boat weighs only 2100 lbs, 1100 of which is in the ballast keel casting.) I didn't normally tow with my wife's forester, but on this particular day she wanted my Dakota for something or other.


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PostPosted: July 21, 2014, 7:05 pm 
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I suggest anybody wanting to build an extra low, single axle trailer to consider pulling into driveways or turning onto inclined roads. Ground clearance at the rear is reduced as the hitch moves up. A low hitch can also hit the ground and gets lower depending on the tongue weight.

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Last edited by Miatav8,MstrASE,A&P,F on July 21, 2014, 8:15 pm, edited 1 time in total.

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