As you may or may not now I'm gonna be on my work placement soon, where I'm going to be drafting parts in cad so I thought I'd do a project or something

Description

As the ones on the market are pretty expensive I thought I would have a go at designing my own, using the strength of 8.8 bolts to remove my crummy welding from the equation.

I noticed most of the current ones on the market do not have braking systems which means you legally cannot tow a vehicle that is greater than 750kg.


Description

So I've made a part for a miscellaneous car master cylinder which is actuated by an over-run system like a caravan. It would either be plumbed to an actuator pressing the pedal, or if the car is knackered you could plumb it straight to the braking system.


Description

In between the two sliding RHS there will be 3mm ptfe sheets to lubricate it. (oooeer!)


Description

The front wishbone of the car is pushed into the groove and a ratchet strap is mounted onto the flat plate which loops over the edge.

I've calculated the loads and even with a factor of safety of 5 and a car with a 0-60 rating of 5 seconds, on a 10 degree uphill gradient, pulling a 1500kg car, you only need 176.6mm^2 of mild steel with a UTS of 300MPa. Negating any shock loads or side loadings.

It is only a prototype at the moment, the only problem I can see at the moment is it probably needs the bumper of the car removing as the wishbones are normally behind it.

So on the DVLA website it points out that as soon as an a frame is attached to a car it ceases to be a car and becomes a trailer, and it implies that the car being towed does not need to be taxed or MOTed, just needs to be lit properly, with the tow cars number plate visible, and not likely to fall apart on the road!

I was looking into this as it would greatly ease the sourcing and transportation of a kit car donor . Apparently a 1128kg ford sierra is no match for a diesel ford galaxy

Pete

The problem with using the towed car brakes, actuated by over-run on the A-frame drawbar, is they are not 'trailer specific' and as such, can't be considered as trailer brakes. It is for this reason that A-frames, braked or un-braked, are for 'recovery to a safe place only'.

This is not what the DVLA website says, it says the use of dollies (two trailer wheels) is for recovery.

"If you attach an A-frame to a car in order to tow it with a larger vehicle, the car plus A-frame counts as a trailer."

If you don't use the car brakes, there are no other wheels you can use!

People who have motorhomes have been towing smart cars legally for years, I find it hard to believe that in every single case of someone towing one, not one traffic cop would have stopped them.

The dolly counts as a trailer towing a trailer.

"If you use a dolly to tow a broken-down vehicle, the dolly counts as a trailer."

Plus the towed car must be road legal, tax mot and insurance unless its going to an mot garage for work then it only needs insurance

Going back to your design. I have a Aframe at home so can compare. Your legs going to the wishbones need to be much longer (depends how accurate you meant the drawing to be) also you dont want to use ratchet straps over the wishbones as they will get worn through. Chains that pull tight over the wishbone which are then attached to the ratchet straps for tightening.

Pete, I've been there, seen it, invested time, money and effort and had no money left to buy the tee-shirt. I see dozens of off-roaders on A-frames attending an off-road course up the road from me, and dozens of little cars behind campers at the campsites. I've also seen thousands of cars pass me at well over 70mph on the motorway but that doesn't make it legal.
If you're saying the towed car is now a trailer, it has to have trailer specific brakes.

It clearly says on the website that a vehicle with an A Frame BECOMES a trailer, nowhere does it say it has to be MOTd or taxed, trailers do not need MOTs or tax.

This site has a bit of a summary regarding legalities;

http://www.smart-tow.com/legal.htm

It's also interesting to see what they did for the overrun braking method, which is what you're aiming for?

I've also seen some suggestions that reversing can be difficult, I guess that triggers the overrun brakes? It's something to consider...

[Edited on 1/7/12 by Slimy38]

Hi Pete.

It's just my opinion, but I would question the use of bolts as opposed to a fully welded construction.

The winch for my trailer came with a "top hat" mount so I made a cross member to bolt it to.
As I didn't want to mess up the galvanized chassis I bolted the cross member to the chassis.

I folded the front & back edges of the 2.5 mm galv sheet to stiffen it, and used M8 8.8 bolts to fix it on.


As you can see in the second close up pic the sheet has bent. Now it's not going to fail completely
but it does show the limits of bolting flat sheet to a box. Had I not folded the edges the result
would have been much worse.


Cheers
Paul G


winch mount


winch mount. bent sheet

Have I missed something, because I cannot see an easy way of connecting the a-frame brakes to the towed car brakes.
Unless you are considering one of the clever mocal connectors, and having the car set up to be connected (ie a dedicated a frame/car setup)

quote:

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Any braked trailers manufactured after April 1989 must be fitted with a hydraulically damped coupling and auto reverse brakes to give braking efficiencies required by EEC Directive 71/320 (ECE13).

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This is an interesting one. I see regularly, motorhomes towing a small car behind on what looks like an A frame. So there must be some kind of legal way to tow a car using a frame design?

Maybe the motor home manufacturers know of a product that does this safely and legally??

Just a thought.

Long story short......
It's not legal but the BiB, courts, VOSA and DVLA can't pick the bones out of the legislation, so no-one says anything. There will be a point where a case goes to court and a precident will be set, but until then.......
I spent months chasing the various authorities for answers and got the definitive answer but it involves trawling dozens of EEC Directives, which have very little to do with any UK application but makes up the legal mess you need to navigate to get an answer.
In short:
If any of the towed vehicle wheels are touching the road, it has to be fully road legal.
If the towed vehicle weighs over 750kg OR has brakes fitted, they have to be trailer specific brakes (ie damped and auto reverse). So even if your little car weighs less than 750kg but has brakes, as all cars do, they have to be trailer specific...
There are regulations apertaining to the towed vehicle brakes being directly coupled to the integral braking system of the towed vehicle(not just acting on the brake pedal) but the brakes still need to be trailer specific but negates the need for the servo/power assistance to be working.

Grey area.
I've heard all sides of this argument.
My brother in law has been pulled literally dozens of times. Traffic cops usually say as its not for recovery he's not allow to carry on with his journey.
Not once has anyone taken it further. No prohibition notices, no convictions and when asked directly what the law states on the subject, not one reply.
This has been going on with him for years.
He has had a couple of producers and there was a law stated on it about why they have stopped him. I investigated it to find the law that he had broken. Turns out that the law the traffic officer has stated was actually just the law that says they are allowed to stop him.


I think the biggest problem is that most people who say they are illegal quote the 'the car becomes a trailer'. That is utter crap. If it 'becomes' a trailer then everything about the towed car HAS to meet trailer regulations, which are as complicated as with a car.

The truth is, the law as it stands does not fully cover it and does not give a definite answer what is legal or not.
The ONLY people who can define this is a judge.

I work in a profession where I have to build vehicles to Construction and Use regs. There are numerous books that interpret the law, but not one of them can be used legally as they INTERPRET the law. eg, if the law says a flashing light on a car is an indicator, can I interpret that as a flashing brake light is an indicator? NO. But a judge CAN interpret it like that. It doesn't change the law. And laws can take years to get amended.

The ONLY way for this to be resolved is for the law to change.
Until then no one can say they are or aren't legal.

As for the OP's project.
I too like to make things, but this is a safety critical item. I would not be happy making a towing dolley. You could design it to pull the weight of the car, but what G loads are you going to put in? What FOS are you going to use? If you have an accident you would be in major trouble. My brother in law had one of his chains snap on his a frame whilst towing. He managed to explain that there must have been a defect in the chain link, but if it had been a home made A frame then I'm sure he would not have got away with it.

Seriously, £200 is not a lot to spend in one.

Surely it would be better to do a project on something else, rather than a piece of equipment in such a 'grey' area.

Also, as said, using bolt construction means you have to use thicker materials, thereby increasing weight on a product where weight is very important due to the 'unbraked' trailer rules.

And, you can buy A-frames for next to nothing!

[Edited on 1-7-12 by designer]

This is the official interpretation from the DfT. As above, its an interpretation, not law as such, but being from central government it's as close as you're going to get:

http://assets.dft.gov.uk/publications/dft-information-sheets/a-frames-and-dollies.pdf

Yes, as said, that's an interpretation and it references:

"Regulations 15 and 16 of C&U set out the braking requirements - including minimum braking efficiencies for trailer brakes. Subject to certain age exemptions, the regulation requires the braking system to comply with the construction, fitting and performance requirements of European Community Directive 71/320/EEC along with its various amending Directives. Alternatively the braking system can comply with the corresponding UNECE Regulation No.13.09."

Which is where things get squirrelly.......

Isn't it easier to make a caravan chassis trailer? For a weekend car I'd seriously consider storing it ON the trailer to save space and just ensure it's secure but I'm not sure about the legal ramifications of that - it could be that the theft insurance is invalid when on a trailer.

ignoring the legal side,i have towed with an a frame once (sierra pulled by sierra p100)
before you ask i did release the steering lock on the towed vehicle.
it took a lot of steering effort to turn and the same again to staighten up.
i stronghly recomend you dont use an a frame (at least for similar sized vehicles)
ive also used a "spectacle trailer" and found it much easier to live with

quote:

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Originally posted by 907
Hi Pete.

It's just my opinion, but I would question the use of bolts as opposed to a fully welded construction.

The winch for my trailer came with a "top hat" mount so I made a cross member to bolt it to.
As I didn't want to mess up the galvanized chassis I bolted the cross member to the chassis.

I folded the front & back edges of the 2.5 mm galv sheet to stiffen it, and used M8 8.8 bolts to fix it on.


As you can see in the second close up pic the sheet has bent. Now it's not going to fail completely
but it does show the limits of bolting flat sheet to a box. Had I not folded the edges the result
would have been much worse.


Cheers
Paul G


winch mount


winch mount. bent sheet

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Got to agree with you on that one - that sheet was not up to the job.

To me the legality side of this is the only issue I have with an otherwise interesting sounding project. Personally I'd spend my time designing a 7-capable trailer following the principles of the locost.

quote:

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Originally posted by owelly

quote:

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Any braked trailers manufactured after April 1989 must be fitted with a hydraulically damped coupling and auto reverse brakes to give braking efficiencies required by EEC Directive 71/320 (ECE13).

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Normal car brakes do not have any auto reverse capabilities. And the Directive also mentions the effects of any servo/power assistance when calculating efficiencies.

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quote:

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Originally posted by owelly
If the towed vehicle weighs over 750kg OR has brakes fitted, they have to be trailer specific brakes (ie damped and auto-reverse)

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And I think you'll find that the damper is in the coupling and has nothing to do with any anti-snaking device. It's there to help with the effects of harsh braking causing the trailer brakes to lock-up.

The regs state what sort of brakes you need to have. Saying you can make the 'trailers' brakes work in the same way doesn't change what the rules say. It's a bit like saying "I know I can't tow an unbraked trailer that weighs more than 750kg, but I've attached -50kgs worth of helium ballons to it so it can weigh 800kg..."

But, if you think you have got it all in hand, good luck with the project.

The damper is required as part of the 'compatibility' requirements for the braking system. With inertia overrun systems brakes are actuated by the trailer pushing against the car when the car starts to decelerate (obviously!), once the trailer brakes come on the pushing then reduces, this cause the trailer brakes to release and then the trailer wil start pushing the car again. The damper prevents this undesirable 'resonance', and as Owelly says, also prebents the trailer brakes coming on too hard at the initiation of harsh braking. There are calculations to define the damping required.

For related reasons, there are complicated compatibility calculations which define how much brake torque at the wheels should be given for a given force on the coupling head.

In theory you can obviously do the calculations to meet the above, and you can engineer an auto-reverse system, but there is one big sticking point. ECE Regulation 13 states:

quote:

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5.2.2.2. Trailers of category O2 must be equipped with a service braking system either of the continuous or semi-continuous or the inertia (overrun) type. The latter type shall be permitted only for centre-axle trailers. However, electrical braking systems conforming to the requirements of Annex 14 to this Regulation shall be permitted.

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Interestingly I have towed a 1.5 ton trailer without a damper on the brakes, or auto-reverse, and it functions to this day just fine. It does have a tendency to lock the trailer brakes on hard braking but only for a second or so. The lack of auto-reverse has never been a problem as there's sufficient friction in the coupling that even over mildly rough ground the brake never actuates.

But if I were designing one from scratch and putting my name as an engineer to it, with knowledge of current regulations, I'd be a fool not to follow the regs. You're going to have to be careful not to fall down the "a little knowledge" pothole here.

The other grey area in the 'A' frame debate is the year that the trailer regs came in, which if i remember is 1982 or 1984 (somewhere there any way). If the car(or trailer depending on your view) being towed is older than that....does any of it count

Prior to those regs coming in it was just if a trailer is over 750kg it needs working brakes.

If i'm going to a rwyb for a weekend i pull my Kitten (1976) behind my motorhome with an A frame, never had a problem and never been pulled over.

The kitten's under 750kg and older than the current regs, and that's the defence i'd use if i was ever pulled by plod.

Ian

I cant see the age of the car mattering one jot to be honest. That is the manufacture date of the car, not the trailer. When did the car become a trailer? Most likely when you attached your A frame.

If you're saying a car becomes a trailer when towed on an A frame then it wasn't a trailer until you attach it. If you took a big steel box made in 1976 and attach wheels and a drawbar it doesnt mean it's a trailer manufactured in 1976.

I too have towed cars on an A frame but have accepted that it's not strictly legal and taken the chance. Does a twin axle trailer not have to be braked equally between it's axles? A car isn't equally braked.

I dont think the arguement that it's neither illegal or legal stands up. It either meets legal requirements or it doesnt!

I cant even fit my a A frame to my kit car as it doesnt clear the steering rack arms anyway.

See if it were a TRAILER rather than an A frame, no-one would bat an eyelid at you as they'd assume it all complied. If it's an A frame the police will look at it as a recovery device and raise questions. Theyre bad news all round.

Which ever way any one wants to look at them, if there was a definitve 'they're illegal' then no one would use them and if they did they would have been some prosecutions. As it is no ones ever been prosecuted or a case taken to court which suggests that there's no clear cut yes or no.

I'll use mine until there is

Ian

There doesnt have to be (nor can there be) a definitive They are illegalillegal as there are too many variables from case to case. As I see it the fact stands that if you use them and your 'Trailer' is road legal than it is legal, if it isn't then you're not! If you build a trailer in your back garden and use it on the road it has to meet legal requirements, as does the trailer you make when you attach an A frame.

Police don't go round pulling in trailers evry time they see one to check legality either, that doesnt mean they are legal. I would be more concernedof being involved in an accident while towing with a trailer which wasn't 100% legal than I would the police stopping me. An insurance company trying to get out of a big payout will start digging more than any roadside police officer. As said tho, I've done it before and most likely will again, I'm not saying A frames shouldn't be used but question whether they are 100% legal (in most cases of use).

I think most kit cars would be grand (if you can get your A frame to fit) as they will be below the weight limit for unbraked trailers. That being said, your unbraked trailer cant be more than 50% the weight of your tow vechile, so if that's 1100kg then maybe not!

There are too many variables for it to be clear cut, but the law will stand as to what is a legal trailer and what isn't.

quote:

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Which ever way any one wants to look at them, if there was a definitve 'they're illegal' then no one would use them and if they did they would have been some prosecutions. As it is no ones ever been prosecuted or a case taken to court which suggests that there's no clear cut yes or no. I'll use mine until there is

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quote:

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Originally posted by balidey
As for the OP's project.
I too like to make things, but this is a safety critical item. I would not be happy making a towing dolley. You could design it to pull the weight of the car, but what G loads are you going to put in? What FOS are you going to use? If you have an accident you would be in major trouble. My brother in law had one of his chains snap on his a frame whilst towing. He managed to explain that there must have been a defect in the chain link, but if it had been a home made A frame then I'm sure he would not have got away with it.

Seriously, £200 is not a lot to spend in one.

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Why not make your car break down and then A frame it?

If you get pulled over then tell them your recovering it. You could tell them its blown or has an electrical problem and wont start.

I could just remove my immobaliser fob and try to start it. Many an AA man has been called out and recovered cars due to dodgey alarms.

Gets round all your issues and arguments.

Yeah, the only problem I had visions of using this to get a donor car, and most donor cars do not have mot or tax so it would be hard to say "well it broke down as soon as the MOT and tax ran out simultaneously" xD

I don't think this would be any more unsafe than if the towball broke on a 1100kg trailer, they are rigged to pull the brakes on so they do not roll out of control and considering I'm using a FOS of 5 with way over the odds forces to begin with, and at the very thinnest section is 40mmx40mmx3mm mild steel. Which from my maths would take over 28kN to reach 1/5th of it's ultimate tensile strength.


And for every square meter of mild steel it takes 300 million newtons to take it up to it's ultimate tensile strength!

So, just going back a bit - what's wrong with paying £50 to rent a legal trailer for half a day? I recently paid £60 for a chap to transport my tin top from storage to my house 30 miles away including him, his fuel and trailer use. Is this because you need the heavy trailer license to tow a heavy vehicle?

I come from a long line of engineers in my family. My Grandad actually made a washing machine and a fridge back when they were new concepts and incredibly expensive. To my knowledge my dad never did any appliances like that but if he ever needed anything, instead of paying well over the odds for £50 worth of materials it is a lot more satisfying to have designed and made your own device instead of parting with hard earned cash that you could spend on something else. It is a mindset that has always been in my family and I would not have it any other way.

When ever I say "I fancy building a....." My mother always points out how similar I am to my grandad

If you have designed and built something you can be proud of it, you can even put it on your CV, it is practical proof that you can design and build something to a specification.


As it is with this I would need my dad to tow it if the weight with a large car would go over the max 750kg limit for persons who pass their test after July 1997 but it is mainly so that I have some piece of mind that once I get my kit car chassis it won't just become a massive immovable object, I will be able to transport it behind a car, until it is finished.

[Edited on 4/7/12 by vanepico]

quote:

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I come from a long line of engineers in my family. My Grandad actually made a washing machine and a fridge back when they were new concepts and incredibly expensive. To my knowledge my dad never did any appliances like that but if he ever needed anything, instead of paying well over the odds for £50 worth of materials it is a lot more satisfying to have designed and made your own device instead of parting with hard earned cash that you could spend on something else. It is a mindset that has always been in my family and I would not have it any other way.

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quote:

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As it is with this I would need my dad to tow it if the weight with a large car would go over the max 750kg limit for persons who pass their test after July 1997 but it is mainly so that I have some piece of mind that once I get my kit car chassis it won't just become a massive immovable object, I will be able to transport it behind a car, until it is finished.

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Here's an update straight from the horses mouth, no hearsay and no speculation.

quote:

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Dear Mr Savage

Thank you for your email of 6 July to the Department for Transport concerning your project on making an A-Frame for the safe transportation of vehicles. This has been subsequently forwarded to the International Vehicle & Standards Division as we have policy responsibility for vehicle safety and as such I have been asked to reply

Our view is that for the purpose of the Road Vehicles Construction and Use Regulations 1986 (C&U) which must be met by all vehicles used and registered in the UK, vehicles towed using an A-Frame can be treated as a trailer when determining the applicable technical requirements. However, separate legislation applies to the taxation of the vehicle and this will continue to apply, ie any vehicle would need to be correctly taxed and insured.

UN Regulation 13 applies if a manufacturer intends to approve a trailer for sale throughout Europe. It is not possible to approve an A-Frame as a trailer instead the national requirements in each member state apply ie in the UK C&U. It is our understanding that this permits an inertia overrun device. However, please see attached information sheet on the need to energise any vacuum on the vehicle and as you mention the need to disengage the system when reversing.

I hope this information has been helpful.

Yours sincerely
Fran Simpson

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quote:

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Dear,
I am looking to make a car towing A-frame for the safe transportation of vehicles. The sentences written on the direct.gov.uk website imply that the towed vehicle does not need to be ‘roadworthy’ i.e without MOT or TAX because it says
“If you attach an A-frame to a car in order to tow it with a larger vehicle, the car plus A-frame counts as a trailer.”
http://www.direct.gov.uk/en/Motoring/DriverLicensing/CaravansTrailersCommercialVehicles/DG_192285
as long as it holds up to the trailer safety regulations, with braking and lighting, and visible towing vehicle’s number plate.
Another problem I have run into is the braking legislation for trailers (vehicle + A frame) in excess of 750kg. In this information page from the Department of Transport dated September 2011:
http://assets.dft.gov.uk/publications/dft-information-sheets/a-frames-and-dollies.pdf
It mentions that the usage of an overrun system (the force of the trailer pushing on the towing vehicle used to actuate the brakes) Is acceptable for braking however there is a regulation under the name of UNECE Regulation 13 on the subject which is dated some time in 2008 showing the following:
“5.2.2.2. Trailers of category O2 shall be equipped with a service braking system either of the continuous or semi-continuous or of the inertia (overrun) type. The latter type shall be permitted only for centre axle trailers. However, electrical braking systems conforming to the requirements of Annex 14 to this Regulation shall be permitted.”
http://www.unece.org/fileadmin/DAM/trans/main/wp29/wp29regs/r013r6e.pdf
It looks to me as if the bold part of the regulation has been put in purposefully to disallow the towing of vehicles on A frames because they do not seem to be classed as ‘centre axle trailers’ and from what I can tell they are the only case where a trailer would not be centre axle, bar an HGV trailer. I was wondering does this regulation apply to us in the UK? I found a page on a .ie site that refers to a slightly different version of this regulation. The letter is dated june 2011.
“O2 trailers will be required to be fitted with semi-continuous or inertia (overrun) brakes. Any such inertia (overrun) type brakes shall allow the trailer to be reversed with minimum drag and must work automatically in reverse and disengage automatically in the forward direction.”
http://www.rsa.ie/Documents/Vehicle%20Std%20Leg/Information%20Notes/Stakeholder%20Information%20Note%20on%20Braking%20Amendments.pdf
I understand that it is required to be able to allow the vehicle to reverse without resistance and provide some damping to avoid harsh braking scenarios.
I deeply thank you for any light you can shed on these incoherencies in different regulations,
Peter Savage

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Still means that your vehicle needs to be taxed and insured, which means the car needs to be MOT'd.

You intend to use it to transport your car while it's not complete - so you'll struggle to MOT it and MOTing it before IVA will prove difficult too?

If a car is not registered yet, then it isn't a car. It is a tubular frame with 4 wheels attached to an A frame. Once it is finished then it would be taxed and insured, then it can be towed.

If I were to get a sierra that was not an MOT failure and had tax I could tow it.

The term 'motor vehicle' is defined in section 185(1) of the Road Traffic Act 1988 and section 136(1) of the Road Traffic Regulation Act 1984 as "a mechanically propelled vehicle, intended or adapted for use on roads".

A couple of cases and stuff here: http://www.cps.gov.uk/legal/p_to_r/road_traffic_offences/#definition

A guy up the road from me went to court to appeal a conviction for keeping a vehicle on the road (although technically, it wasn't on the road but was still in a public place) with no tax, test or insurance. His agument was that as the car had no engine, it was no longer a road vehicle. The judge took a dim view of this and said something along the lines of: "to any man, it looks like a motor vehicle. It is intended to be used on the road therefore it's a motor vehicle".

The guy up the road got the book thrown at him for just about everything they could drag up.

As has been said many times on here, if you want to chance it, go ahead. But lets hope the judge isn't a Locoster.....