Tow hitch for The Fire Bike, part 3 – 29 Jun 2016.

Here is the final part of my story about fitting a tow hitch to The Fire Bike. While the paint was drying/hardening on the pannier/towing bracket I turned my attention to the towing electrics.

I wasn’t sure if I was going to use the standard 7-pin UK towing socket and looked for more compact alternatives. However, I couldn’t find anything I liked better. I decided the best place to mount it was beside the number plate to a bracket sandwiched behind the plate. I drew a card template then cut the bracket out using my old “Monodex” cutters which I’ve kept from my car restoring days.

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It will screw behind the number plate using the lower mounting bolts.

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I trial fitted this to the bike but found it rattled and needed 2 additional small screws to reduce this. Here you can also see that the bracket has been bent forward so the socket will clear the left hand pannier when fitted.

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It was clear to me that, If I wasn’t careful there would be a “rats nest” of wires below the tail lamp and behind the number plate. This was because I still wanted to keep the connections for the lights I’ve fitted to my top box. Piggy-backing connectors together wasn’t going to be the answer. I decided to use a connector block which would allow four way connections. Only ones with screw down terminals were compact enough. The top connections would be for the wires from the bikes’ main loom and to its original lights. The lower connections would be for the top box and trailer wiring.

I cut the terminals from my top box wiring and replaced them with ring terminals and made a short ground connection.

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Then I added ring terminals to the end of a length of 7-core trailer cable. Only 6 of the wires are used. The blue one is for a fog light and is held out of the way with heat shrink.

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Rather than remove the terminals from the bikes’ wiring I made a pile of adapters and fitted them to the connector block. There is also a link joining terminals 2 and 3 together. This is because trailer wiring usually has left and right side tail lamps on separate circuits but, of course unlike a car, a bike only has one to feed them.

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The connector block was fitted with a bracket so it could be mounted to the lower tail lamp bracket bolt and the bike wiring connected up and tested.

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It’s still a bit “busy” back there and I might end up changing the bike wiring to ring terminals and junking my adapters after all.

I fitted the top box and trailer connections to the lower part of the connector block and then checked the number plate hardware would go back without trapping the wiring.

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The towing socket was wired up and fitted to the plate I made using its rubber seal. These sockets are easy to connect up and wiring diagrams are easily found on the net.

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Next the trailer wiring and top box connections were tested. Everything worked as it should.

The paint on the tow bracket was still not hard enough to handle so instead I gave the bike a wash to get rid off all the sand/dust that came down in the rain the other day.

This afternoon I remounted the chrome top rack and fitted the new pannier/towing bracket. I had to go and borrow a 1 1/8 in spanner to fit the tow ball to the bracket. It had to be held with a Stillson pipe wrench but I managed not to scar it. The panniers finally went back on and the job was pretty much done. I just added a rubber buffer to the back of one of the towing socket screws so it can’t dig into the pannier when I plug the trailer in.

I think it all looks OK.

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I need to hitch it up and go for some test rides now.

Oh, just one more thing. I made up a kerb weight plate for the bike and an unladen weight plate for the trailer. They’ve been stuck on with some double sided tape designed for fixing badges to car bodywork.

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Update 30 Jun 2016.

I have made a little change. Looking at the photos last night I was concerned that the socket for the trailer electrics obscured the “6” of the number plate too much (also see the comments below). I’m not concerned about the plug obscuring the number plate when the trailer’s plugged in as there’s a number plate on the back of that. It’s actually legal to remove the plate from the tow vehicle and fix it to the trailer. The UK regulations state;

“A registration plate must be fixed on the rear of—
(a) the vehicle, or
(b) where the vehicle is towing a trailer, the trailer, or
(c) where the vehicle is towing more than one trailer, the rearmost trailer.”

So there you go!

There isn’t clearance to fit the socket below the registration plate so the best I could do was to raise the socket in line with the top line so it will only cover the blank space next to the “E”. The regulations that apply to the old-style plates say there must be a 10mm margin beside the letters/numerals and there is 40mm here. I could have a plate made with the top row aligned to the right giving even more space but that, though legal, would look a bit odd.

Here are photos of the revised set-up with the bike solo and with the trailer plugged in. I should have done this in the first place.

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3 thoughts on “Tow hitch for The Fire Bike, part 3 – 29 Jun 2016.

  1. Yes. The plug covers the 6 when the trailer is fitted but I don’t think this matters when the trailer is on. I’m more concerned that the socket partially hides the 6 without the trailer if you’re viewing it from the left. I might remount the socket up beside the E or below the plate if I can make something fit.

  2. As you can see, I revised the positioning of the tow socket and have updated the post. It’s much better like this. I had originally been worried about the reach of the trailers cable but it’s fine.

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