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BuckBlu110

Member Since: 19 Apr 2014
Location: in the pub
Posts: 712

1994 Defender 110 BMW M57 3.0 Diesel CSW Buckingham Blue

Advice needed about a tow bar.

I’ve finally managed to get hold of a penman trailer to replace our old wide track, which I’ll be putting the camping gear in and roof tent on, under normal circumstances, I would tow it with the 110 and a nato hitch but having suffered a couple of major break downs recently, thankfully not towing the trailer, I would like the option to tow it behind either our freelander or discovery, or even a recovery truck if any of the above broke down whilst towing it.
I’ve seen a couple variations of emergency adapters from nato lunette to 50mm ball, such as:

And this, which I believe is Landroveranoraks or very similar.

Click image to enlarge

I have now got an idea of how I can get an adapter to work whilst still keeping the brakes:

My question is, if I was to add a section and pair of braces that I’ve marked in the above photo, and a similar setup to the the other two for attaching to the nato lunette ring, would this design be strong enough?
I’m using 5mm steel box tube and 12mm plate for the conversion and will be welded by a friend of mine that welds for caterpillar so I can be sure the welds will be up to the job. I’m also running the main of the tubing through the piece of box section that’s underneath the hitch to reduce any side to side and up and down movement and twisting.
But will this design cause too much stress on the lunette or hitch?
The last thing I want is snapping off going down the motorway!

12th Feb 2022 4:51pm

Bluest

Member Since: 23 Apr 2016
Location: Lancashire
Posts: 4206

2007 Defender 110 Puma 2.4 XS CSW Java Black

You might find that a recovery driver will take a look at the home made adapter and say “no way Jose”. It may be perfectly up to the job, but how would they know? 2007 110 TDCi Station Wagon XS

12th Feb 2022 5:20pm

camelman

Member Since: 27 Feb 2013
Location: Peak District
Posts: 3368

Where is the movement in your design to allow the brakes to function?

12th Feb 2022 5:25pm

BuckBlu110

Member Since: 19 Apr 2014
Location: in the pub
Posts: 712

The recovery driver doing that is always a possibility I suppose, not sure how to get around that though.
Hopefully this pic will help me describe the brake situation:

So there’s nothing stopping the lunette from sliding back to operate the brakes as normal, so the whole adapter it fixed to the lunette but the lower part/tube which the 50mm hitch is bolted to slides under the draw bar in the box section circled in yellow to hopefully reduce leverage movement.
Hope this makes sense?

12th Feb 2022 5:59pm

blackwolf

Member Since: 03 Nov 2009
Location: South West England
Posts: 17353

2007 Defender 110 Puma 2.4 DCPU Stornoway Grey

Without wanting to rain on your parade I have to say I wouldn't dream of towing a trailer fitted with a NATO 76mm lunette with a home-made hooky lash-up like those shown, even in an emergency, on a public highway or in a public place.

A Penman will be new enough to have cat O2 type approval which will be invalidated immediately by any hitch modification. This may be significant in the event of an accident, insurance question, or police or VOSA check. If it looks hooky, which those certainly do, the chances of a "tug" are very high. Worst case you get your stress calcs wrong or there's an inclusion in your weld, the contraption breaks off, and the trailer kills the family coming the other way. Is it worth it? Are you that confident in your fabrication?

If you're worried about recovery, fit your type-approved pintle to a type-approved DB slider and fit a type-approved DB multi-height hitch on the Defender, most light recovery vehicles use this system so they can recover any type of trailer. The operator can borrow your pintle. You can use the same system on a Disco2 although the trailer nose will be very low. I don't know if this kind of hitch was available on later Discos, and I don't know of any way to tow a military trailer legally with a Freelander.

If you must tow the Penman with a 50mm ball hitch get someone with public liability insurance to modify it properly using an unmodified type-approved coupling and submit it for an IVA afterwards.

12th Feb 2022 11:17pm

camelman

Member Since: 27 Feb 2013
Location: Peak District
Posts: 3368

Im afraid I agree with the above. The consequences of the modifications failing don't bear thinking about.

The penman is a heavy old trailer even when empty at 600+ kg.

Its bad enough if the trailer starts to snake in its standard form but any snaking with the proposed arrangement would put huge lateral loads on the modified components.

Photo for reference 😉

13th Feb 2022 4:48pm

BuckBlu110

Member Since: 19 Apr 2014
Location: in the pub
Posts: 712

Thanks guys, as always, much valued insight taken on board. As I said before, the last thing I want is the trailer coming off going down the motorway, or anywhere for that matter!
I’ll leave well alone.

13th Feb 2022 6:30pm

BuckBlu110

Member Since: 19 Apr 2014
Location: in the pub
Posts: 712

Just to round this thread off, after talking to a couple of trailer fabricators and getting plenty more advice, I settled on Blackwolf’s idea and got a fabricator with plenty of experience in this sector, to weld me a new draw bar, to which we fitted a knott 50mm coupler with the correct load rating. We even got the brakes fixed up and working correctly.
For the next step, I spoke to my local test center for a IVA and they recommended I speak to vosa first, so I emailed Vosa and asked what steps need to be taken for a modified trailer and IVA, their response was essentially, If the manufacture date of the trailer remained before June 2012, then an IVA would not be needed.
Since then, Ive used it a bit for small jobs and it tows wonderfully, probably better than it did with the nato lunette.
Ive also just completed a 600mile round trip around Cornwall after I fitted a hinged lid and bolted our roof tent to it. It never missed a beat!

Click image to enlarge

17th Sep 2022 10:46am

blackwolf

Member Since: 03 Nov 2009
Location: South West England
Posts: 17353

Thank you for providing the update to this thread. I am absolutely certain that you made the right decision and the finished product totally justifies your decision, it's one of the best adaptations I've seen.

17th Sep 2022 11:16am

BuckBlu110

Member Since: 19 Apr 2014
Location: in the pub
Posts: 712

Thanks Blackwolf, when I get chance, I’ll get some more photos up

17th Sep 2022 3:00pm

Screbble

Member Since: 26 Apr 2015
Location: Lancashire
Posts: 2081

2004 Defender 90 Td5 XS CSW Zambezi Silver

I’ve often wondered about the conversion from a NATO hitch to a std 50mm ball - how it is done legally and safely to be specific - and now I know!

Good job well done 👍

17th Sep 2022 3:22pm

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