Friday, 1 October 2010

Fluid design... well sort of... ...

I'm the sort of person who spends a lot of time thinking about things, all sorts of things, like how can I make this or that, what's the best way to fix this, and loads of stuff in between.
Building things makes me happy, and I think you get a grate deal of satisfaction when you find a problem and solve it, or when you build something from scratch.

With that in mind I have had to re-think the towing hitch for my bicycle trailer, I hadn't really considered it much before because what I had worked reasonably well and so I decided why fix it if it isn't broke ? that is until I realized it could be better, and because what I had was actually causing damage to my bike.

The first trailer hitched to my bike the same way as the second trailer, but it wasn't until I built the second that I decided to re-design the towing hitch, the trailer and the way it attaches to the bike are constantly being reviewed by me, hence the "Fluid design" post title. Basically I used a u-bolt to attach the trailer to my bike by way of a couple of d-shackles, these were the best option for the first trailer, and they work well for this one.

Here's a u-bolt -
U-bolt, which you can find in most hardware/diy shops.
What I did was to buy 2 of them and use the metal plate from 1 on the other, so I had 2 metal plates which I could use to clamp the u-bolt onto the bike frame, it was a pretty easy way to solve the problem of attaching the trailer to the bike.

Here's a very crude diagram of how I did it - 
Not the best technical drawing in the world.
As you can hopefully see I clamped the u-bolt to one of the rear forks of my bike, this was okay for the most part, but I started to notice that after time the bolt wouldn't stay in the right place, and it eventually moved quite a lot, especially when I had heavy loads in the trailer.

Here's a picture of the damage it has cause to the forks - 

You can see all the paint has gone, down to bare metal.
I had attached the bolt to the higher of the 2 forks, and it eventually started to move up and down, the damage on the lower fork was caused by the end of the trailers tow bar moving more than it should have been.

So not so long ago I set about re-designing the towing hitch, and I think I came up with a pretty good solution, I have managed to make a hitch that is easier to use, stronger and most importantly is very stable, it allows parts to move, but the right parts.

Here's the new hitch - 

It's a little rough, but it works.
As you can see by the picture above I still use d-shackles to attach the trailer, but the hitch is much better, I have re-used the u-bolt and the 2 metal plates from the original hitch, but I have added a strip of metal and 2 bolts, the new hitch now fixes to both of the rear forks (on the left side of the bike) the u-bolt makes up part of how it fixes to the bike. It is stuck where it is, it doesn't move in any direction, and hopefully it will stay that way, I just need to patch up the damage, I may just re-spray the whole bike.

Here's a picture of the back of the new hitch - 

The other side of the hitch.
So basically what I've done is to use the 2 metal plates to clamp the hitch to the forks, the u-bolt is in the middle of the large metal plate and using 2 extra bolts I have managed to make a much more secure fixing, which means increased stability when I have the trailer attached, it still moves a little, but it's the right kind of movement.

A picture with the trailer attached - 

I will explain the blue bar.
As you can see the shackles work well, and allow enough movement to be able to hitch and un-hitch the trailer easily. You can also see that I've used and eye bolt in the end of the towing bar and the shackles basically join the 2 to each other, you may also notice the cable that goes through the eye bolt, this is a safety and security measure, it provides a way to padlock the bicycle to the trailer, and should for some reason the towing hitch fail there is a back up, you may have also noticed the towing bar is bright blue :-) this is because I broke the original bar, and had to use this as a replacement, it's an old part of a climbing frame, very strong, but light weight (don't worry I didn't dismantle the kids climbing frame to build this)

And that's about it really, I had to find a better method, and this is it, well I think so, I have used the trailer several times since I made the new hitch and I have noticed a difference in the way the trailer behaves, it is much more stable at speed (not that I go that fast, but it wobbles less when loaded)
I will spray the hitch when I get round to spraying the rest of the bike, so it doesn't rust.

Now for my next trick....... finding a way to get rid of the bike and hitch the trailer to the dog, like a sledge :-) Just kidding.

Here's a pick of the dog -

Meet Pepper, the family mutt :-)

Thanks for reading.

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