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Trailer Design Failure

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Old 10-31-07, 07:19 AM
  #1  
HandsomeRyan
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Trailer Design Failure

Last night I built the beginnings of a bicycle trailer out of 'screwed and glued' 2x2 lumber. Instead of fabricating some type of removable skewers for the wheels (salvaged from my wife's childhood bicycle) I just used the original threaded rods that held the bicycle wheels to the bike. After completing assembly of the entire "platform" section, I realised a design element I had overlooked- short of cutting apart the 2x2 braces that hold the wheels on, there is no way to change a flat tire. Oops.

A very silly and easily preventable mistake, but I'm sure I'm not the first person to do this.

The lesson: If you are building a trailer, be sure to design it to allow wheel removal.

I'll try to post some pictures of the trailer once it is complete but I still need to add a deck, cargo box, and hitch assembly.
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Old 10-31-07, 10:42 AM
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Boy, I sure hope you used oak for your framing wood members.
If not the holes in the pine/fir 2x2 will weaking it to much.

For a source of free white oak see if you can find/salvage a used
shipping skid. Most are made of good hard seasoned white oak
that make dandy strong framing members for a bike trailer.
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Steel: nearly a thousand years of metallurgical development
Aluminum: barely a hundred, which one would you rather have under your butt at 30mph?
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Old 10-31-07, 11:44 AM
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If necessary, you can fix a lot of flats without removing the wheel. It's awkward, but can be done. If this is a trailer you use just everyone once in a while, you could conceivably use it for years without removing the wheels.

They also make the no-flat tubes with solid gel (sell 'em at Walmart). Years ago, I got one and never succeeded in getting it installed. But if you could work it, that would be another solution.
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Old 10-31-07, 01:16 PM
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Originally Posted by StephenH View Post
If this is a trailer you use just everyone once in a while, you could conceivably use it for years without removing the wheels.
That is the attitude I'm taking with it right now. I think Murphy's Law dictates that the trailer will get a flat tire the first time I use it though. I only plan to use this trailer to get things home from a large shopping center that is less than a mile from my house. Even if the trailer fails, it isn't likely to be more than a minor inconvienience for me.


I believe the 2x2's I used are pine. The trailer still seems pretty strong because the holes were less than 1/4" diameter (less than 20% of the diameter of the wood). You are correct though, because all the holes are in a line; too much force on either end could snap the trailer in half. The solid decking and cargo box should help stiffen everything up, but I will consider adding fiberglass reinforcements on the bottom of the trailer in the areas where the holes are drilled if it still looks like this could be a problem.

Mrs. HandsomeRyan and I are going to the hardware store tonight and I'm going to see what I might use to make a hitch. The pulling bicycle already has disc brakes, a rack, and fenders using up all the available mounting holes beside the rear axle. In light of this, I am looking at attaching the hitch to the back of the rear luggage rack. I know the rack was not designed for this type of load, but it is quite sturdy. Because the trailer is well ballanced and I'm far too weak to climb steep hills with a full load of cargo, I believe the rack can handle the additional stresses of being used as a hitch mount. Now the question is what to use as a joint to allow the bicycle and trailer to flex and move independently of one and other but remain tight enough to prevent unnessicary vibrations and chatter. I guess I'll see what is available and build from there.
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Old 11-01-07, 09:22 AM
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I built this wooden trailer in the '80's and still use it today. The one
major change I made was to upgrade the frame to oak (salvaged skid).

There may be some ideas that you can use to build your trailer with
low/no cost materials just as I did.

http://www.motherearthnews.com/DIY/1...e-Trailer.aspx
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Originally Posted by krazygluon
Steel: nearly a thousand years of metallurgical development
Aluminum: barely a hundred, which one would you rather have under your butt at 30mph?
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Old 11-01-07, 11:56 AM
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Tightwad, thanks for the input and the link. I think i may get a chance to use some of your ideas afterall.

I got a call from my wife about 2 hours ago saying that my Father-in-law (her dad) did not realize that I was going to take apart the bike*. Now he wants it back because "it has sentimental value to him."

So today my lunch break was spent cutting apart my almost-complete bicycle trailer to retrieve the wheels so i could reassemble the bike. I do not believe that any of the existing framework is salvagable as anything other than firewood. I guess I'll have a chance to correct my design flaw afterall.

*Did he think @ 6'2", 220lbs that I'd look cute riding this pink Huffy with 20" wheels?
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Old 11-01-07, 05:51 PM
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Bummer on the bike. I will say that when I was a kid my dad built a trailer out of scrap pine 2x? and plywood. It just sat behind the shed for years and thats where we kept all the soda cans that we drank and whatever scraps of aluminum he collected from work (construction) Maybe once a year or so we would air up the trailer (not bike)tires on it and pull it by car to the recycle center about half a mile away. The trailer never got pulled more then ~20 mph if that but it held up for many many years of sitting outside in rain and whatever and having a pretty good load on it. So I believe the pine should hold up fairly well.
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Old 11-01-07, 05:54 PM
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Oh yea, and best of all, he let me keep the money!! $20 is alot for an 8 year old. He also built my a trailer for my bike with a 5 gallon bucket and trashcan wheels with an All-Thread hitch on it. I used to ride everywere looking for cans!! I bet I was the first 8 year old to open a bank account with $100 cash in my town!
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Old 11-01-07, 06:33 PM
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If you check around, you can get bikes that size for pretty much nothing. I was at an auction a while back with a bunch of worthless bikes (police pound) and they typically went for maybe $5 or so. Watch garage sales, etc.
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Old 11-01-07, 06:35 PM
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I just gave away a 20" wheeled Huffy on Freecycle yesterday.
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Old 11-02-07, 06:55 AM
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I'm following a couple leads on free/cheap bikes in this area. I just gave away a 70's model fugi road bike to a guy who needed it to get to and from work. (gotta share the utility cycling love) So I'm hoping that giving away that bike will bring me enough good karma that I'll find another suitable 'donor bike' in short order.

the local thrift store (Goodwill) sells bikes for $8-$30 but most of what they have is all rusty and borderline unusable. I'm stalking Craigslist and especally as people start cleaning out their garages to dig out the boxes of x-mas ornaments I'm hoping some things will come available.
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Old 11-02-07, 07:11 AM
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Lately I have found alot more use out of posting a want ad in the bike section on CL. Alot of people have something they want to get rid of and never get around to posting it or just dont feel like posting a bike they couldnt sell for more them $5. Or just dont feel like the hassle of trying to find someone to buy it. Try it.
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Old 11-02-07, 08:54 AM
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done and done.

I fibbed a little in my ad by saying that I wanted the bike to 'ride' to the grocery store. I worry many people would be less inclined to give away a bike if they were told in advance that the bike will be chopped into little pieces and used to cobble together a franken-trailer. My F-i-L included in this group.
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Old 11-02-07, 04:33 PM
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haha, keep us updated.
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Old 11-02-07, 04:40 PM
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Yeah, my trailer suffered a few complete failiures before I got it right. Broken dropouts, broken dropout holders, broken cross-member thingies, etc etc.

But my best trailer design failiure had to do with the tongue, this part broke repeatedly before I got it right. It's made of wood and sticks out the front left side, goes to the bike's axle. It most often failed at the angle part from carrying loads of a few hundred Kgs. What happens is when you brake or accelerate, it puts lots of twisting force on it. When it's about to come apart, the trailer feels loose.

So if you want to build a tongue so that it won't break, here's what you do: Visualise this part being very well built, at least twice as strong as it needs to be... Do you see it? Ok, now double it & add some metal bits to help resist twisting, and it's just about right. At this point, something else is likely to break first.
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Old 11-04-07, 02:00 PM
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[QUOTE=JeanCoutu;5566307
So if you want to build a tongue so that it won't break, here's what you do: Visualise this part being very well built, at least twice as strong as it needs to be... Do you see it? Ok, now double it & add some metal bits to help resist twisting, and it's just about right. At this point, something else is likely to break first.[/QUOTE]


Yeah I run across that problem with my own homemade bike trailer I just recently built. Since the trailer tongue on my trailer is affixed to the seatpost, I used 3/4-in EMT conduit bent into a backwards "S" design (with the help of a tree) and bolted in three places to a solid piece of 3/4-in plywood under the trailer. The lead clamp is a small U-bolt drilled thru the 3/4-in plywood and bolted down. The clamps directly following the lead U-bolt are 3/4-in metal straps made for affixing 3/4-in conduit to walls and such. The metal straps are a bit flimsy IMO, so thats why I used a U-bolt as the lead clamp. The torsional and lateral stresses dont seem to effect it so far.

If I say so myself, I believe I did a fairly good job building this trailer. I have about $100 in it, including brand new 20-in BMX Mongoose wheels and tires I bought off ebay. The trailer pulls like a dream, with about 2 lbs draw weight on the hitch, and tracks true and straight. I was all set to post a big, nice thread on this project to help others in this forum, but my digital camera took a dump on me at the last minute. (a complete, and utter bummer)

Just as soon as I beg, borrow, or steal another camera I'll post a full spread on it.
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Old 11-04-07, 02:49 PM
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I fabricated my trailer plumbing supplies, some wheelchair wheels that my friend gave me, and some scrap materials from my shop.

Now where's that picture ?
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