mx5 towbar

Vat · Postby **Vat** » Fri Apr 04, 2014 8:55 am

Exocet Australia wrote:I can build you something that'll hold your bike that's removable. Won't cost you an arm and a leg either. Wouldn't be designed for towing a trailer

Watching with interest...

dmad_dood · Postby **dmad_dood** » Fri Apr 04, 2014 9:49 am

Legal complications have been in the back of my head for a while. Im not even so sure a u.s. made tow bar would work for us here in Aus. I think lights would possibly have to be installed along with a number plate as the bikes would impair vision from the back.

When designing just keep in mind that the tow hook mounting points are not exactly parallel with each other, i'm pretty sure they taper out from each other so the brackets wont be exactly square.

Did a bit of digging and found this..

http://www.comlaw.gov.au/Details/F2010C00153

Cheers.

Jono.

greenMachine · Postby **greenMachine** » Fri Apr 04, 2014 11:14 am

I had a towbar custom made for the GM, to tow a trailer. Worked a treat, and still working on someone else's car.

It was as heavy as buggery, bit of a problem for a track car, but the weight was mostly in the tongue (it was a modified junkyard HR unit), and the tongue was removable - problem solved!

The key is that the mounting on the tiedowns needs to be supported to stop the twisting action when a load is applied to the towball. This was done by extending arms back and attaching them to the car's structure, so the bolts on the tiedowns only took forces in shear and tension. This needs to be done for any weight, trailer, bike rack, spare tyre, doesn't matter, as there is a reasonably long lever between the ball and the mounting brackets.

:mrgreen:

Exocet Australia · Postby **Exocet Australia** » Fri Apr 04, 2014 11:23 am

Luckily I'm at Dann's and he has some NA's here so I've been able to have a look.
A removable bike rack will be pretty easy by the look of it. Slide out with locking pins, Powdercoated will probably be about the $400-$500 mark.
If you guys can arrange a group buy, I can drop that considerably. I'll just have to steal an NA from Dann for a day. I've got NB's in the workshop too, so a slight design change can sort that out

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manga_blue · Postby **manga_blue** » Fri Apr 04, 2014 12:06 pm

Hayman Reese for NA, plated at 450Kg. The pics might help somebody ...

dmad_dood · Postby **dmad_dood** » Fri Apr 04, 2014 12:13 pm

I had a tow bar custom made for the GM, to tow a trailer. Worked a treat, and still working on someone else's car.

It was as heavy as buggery, bit of a problem for a track car, but the weight was mostly in the tongue (it was a modified junkyard HR unit), and the tongue was removable - problem solved!

who did the tow bar for you and how much was it if you don't mind me asking?

I was thinking a solid tow bar i.e. no receiver hitch or anything like that, that way it would be stronger and lighter overall but then mounted with 4 winged bolts into the existing tow hook mounts, that way it can be completely removed and installed in a couple of minutes, with zero weight penalty.

Just a thought.

Exocet Australia · Postby **Exocet Australia** » Fri Apr 04, 2014 12:22 pm

Considering a standard 6x4 box trailer is 200kg, a bar rated at 400kg isn't really going to be able to do much conventional towing, but I'll call the Hayman Reece rep and get a price. Are you guys interested in the wiring loom as well?

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Exocet Australia · Postby **Exocet Australia** » Fri Apr 04, 2014 12:35 pm

Just spoke to the rep, Hayman Reece don't make them anymore. Cosmopolitan Towbar don't make them either.

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Exocet Australia · Postby **Exocet Australia** » Fri Apr 04, 2014 12:39 pm

A permanent frame mounted to the tow hook bolt mounts would only be 5-8kg. A frame could then slide in and be held with pins.
I'm back at my workshop and just looked under the NB. I can't see anywhere reasonable that a conventional towbar could bolt to. Still doable, just doesn't have mount points like the NA does

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dmad_dood · Postby **dmad_dood** » Fri Apr 04, 2014 1:08 pm

Would the tow bar need to be engineered?

Exocet Australia · Postby **Exocet Australia** » Fri Apr 04, 2014 1:08 pm

No, it wouldn't. Because you're technically not towing anything.

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dmad_dood · Postby **dmad_dood** » Fri Apr 04, 2014 1:38 pm

Sounds Good

Exocet Australia wrote:A permanent frame mounted to the tow hook bolt mounts would only be 5-8kg. A frame could then slide in and be held with pins.
I'm back at my workshop and just looked under the NB. I can't see anywhere reasonable that a conventional towbar could bolt to. Still doable, just doesn't have mount points like the NA does

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Would this be a receiver hitch/tounge affair?

Exocet Australia · Postby **Exocet Australia** » Fri Apr 04, 2014 1:47 pm

Of a sort, yes. I'd have it slide into receivers on both sides so it's stronger/more stable. I know my road bike is ridiculously light so it doesn't have to carry much weight. You'd be safe carrying your bike plus another easily.

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dmad_dood · Postby **dmad_dood** » Fri Apr 04, 2014 2:14 pm

Sounds good

Keep us posted!!

Cheers.

Exocet Australia · Postby **Exocet Australia** » Fri Apr 04, 2014 2:26 pm

Is it just bikes? If I'm going to design something I might as well design it so that it's multi purpose. That way all you'll have to change is a top mounting bracket

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