Hitch / Coupling Trailer Issues

[Smelly]

I am retrofitting a new hitch/coupling to a drawbar that is 78mm wide but the hole centerd for coupling is 55mm.

I can see daylight when I rest the hitch on top of the drawbar - meaning I don't have enough meat/strength to drill four(4) holes through the drawbar.

What to do? :-/

Smelly

[Black_Jack]

Smelly

My trailer has a big angle metal bit that the hitch is bolted to.... by memory



geoff

[Smelly]

Photo?

[Black_Jack]

Smelly

Attached is photo 1 of 2


geoff

[Black_Jack]

Smelly

2 of 2

geoff

[Smelly]

Great picis..

Thickness of the angle iron aat front and channel section at rear?

[Feral]

I'd weld a 3/8 plate over your draw bar to bolt the coupling to. (I'd drill it before welding!)

[blaze]

personly I would weld a 13mm plate(at least 10mm) flat onto the drawbar, I always feel more is better. Pre drill is a good idea. Dont like the mount of the one in the pics above as the rear mount is only made of 3mm RHS and used for the purpose of what it is there, just not upto the job IMO. I am not trying to pick holes in your trailer Geoff.
cheers
blaze

[blaze]

just to add to the above I would also fully weld the plate to the drawbar
cheers
blaze

[Smelly]

Thanks Boys.

So, basically a plate wide enough and long enough to cover full dim of hitch?

[Smelly]

How far should the plate protude past the front of drawbar or should it be flush with front of drawbar?

[Smelly]

ALso, SHould I weld two plates - top and bottom to make bolts go right through top and bottom of drawbar?

What do I do about using high tension bolts?

Do the bolts need to be of certain length for strength? :-?

[Getout]

Whatever you do , you need to make sure it isn't gonna break. If it does and someone gets hurt you will have a terrible conscience and a big problem on your hands if insurance finds a reason not to pay. When modifying original equipment, it pays to use a professional.
I notice in the photos that the safety chains are bolted to the drawbar. I have a feeling that they have to be welded.

[Smellier]

All,

This is Smelly but at work ;)

I have the plate made (13mm).

But still - I have concerns -

If I am to fully weld plate onto drawbar, how do I access the nuts for the bolts to tighten up ?

Where is the clearance? :o :o

[Smellier]

The bolt holes in the hitch are not clear of the drawbar.

If I place the hitch on top of the drawbar and look down through these holes I see some of the edge of the drawbar (hence daylight) - but the holes are not clear of the drawbar.

How do I attach the hitch the fully welded plate then? ::) :-?

[blaze]

drill and tap a thread in the holes, if your bolt holes in the hitch are 13mm then by tapping 1/2 nc threads into the steel plate you will then have maximun obtainable strenth for the joint. The bolts to put in will need to be grade 5 bolts and not galv ones (paint them with cold galv paint)
cheers
blaze

[finding_time]

I'd weld a 3/8 plate over your draw bar to bolt the coupling to. (I'd drill it before welding!)

Spot on ;)

Ian

[Smellier]

Thanks Blaze.

Damn, I have alradey had the holes drilled out..

Should I go 1 inch thick plate instead?

How do u ensure the bolts do not come undone?

Thoughts?

[darrmun]

i'd stick with the 1/2" plate & use grade 8 or better 1/2"unc bolts ie cat zinc dichromate bolts they are reasonably corrosive resistant as well & drill & tap thread in the plate , you could go up to 5/8" or 3/4" if you really wanted but 1" is a fair overkill

[Cheech]

Like the other guys, I had the impression that the bolts would have been able to go straight through with clearance each side. But as that is not the case, you will still need something similar to your original. The only thing that I see wrong with the original is that the back piece of box section is pretty light. I would just weld your 10 - 12mm new baseplate straight on top of the existing brackets, and also weld on an extra piece of plate or angle iron flush with the back of the box section to connect the new plate directly to the draw bar. This will give the back section the extra strength that it needs.

You may just have to trim/grind the old brackets a bit where the new nuts will end up, to allow room for the nuts before you weld the plate on.

[Smellier]

Holes have already been drilled without tapping (@15mm).

Obvicoulsy the 1/2 tap is too small and I have to start again..? :(

[Smellier]

Cheech,

The exisiting hitch is welded on to the drawbar directly - without any baseplate and looks pretty ancient and has a totally different looking ball lock mechanism. #So no brackets/baseplate currently exist.

I have to cut through the weld of the existing hitch to get the fckr off.. >:(

[Smellier]

Must I make another plate now - with threaded holes this time? :-?

[blaze]

I would make a new plate
cheers
blaze

[Smellier]

What are the hole diameters normallly in these hitches?

I only have a tape measure - so not very accurate..

I measure 15mm but that's with a tape measure

[Smellier]

How do u ensure the bolts do not come undone?

[darrmun]

use some threadlock ( loctite ) & or spring washers

[newchum]

hey smelly/smellier, both of my trailers have the same hitch which is bolted straight to the 75x75x4mm draw-bar the 55mm centres are made to fit on 75rhs, the bolt edge is against the inside wall of the rhs one trailer has a 19ft haines on it the other a 23 carribean also both trailers have recently been for inspections. the mounting bolts stop the rhs distorting inwards and a bolt across the rhs which the chain is attached stops it bowing out

rodney

[newchum]

foregot that both have grade 5 1/2ins galv mounting bolts with double nuts for locking

[Smelly]

Thanks Newchum.

I always thought drilling into wall edges of box section channel would have a weakening effect??

This is why I was aprehensive drilling into the drawbar..

does your drawbar have an internal box section for strength ?

[Smelly]

Newchum,

What hole dia is in your hitch coupling?

Others, what are your thoughts about drilling into the edge of the drawbar channel of the trailer??

Here is the equation :
75mm section & 55mm hole centers & 15mm hole dia (7.5mm radius) & 4mm wall tickness
75 - 55 = 20mm
20 - (2 x 7.5mm) = 5mm (total remaining meat on drawbar)
5/2 = 2.5mm (clearance on each side)
4 - 2.5 = 1.5mm (interference on each side)

How does the bolt go though 1.5mm of steel? :o :o :o

Smelly

[newchum]

smelly the hitch holes are 15mm, the bolts and holes in the rhs are13mm
as i posted before the bolts are hard up against the wall of the rhs
do you want some pics , can do it tomorrow

rodney

[newchum]

Newchum,

What hole dia is in your hitch coupling?

Others, what are your thoughts about drilling into the edge of the drawbar channel of the trailer??

Here is the equation :
75mm section & 55mm hole centers & 15mm hole dia (7.5mm radius) & 4mm wall tickness
75 - 55 # #= 20mm
20 - (2 x 7.5mm) = 5mm (total remaining meat on drawbar)
5/2 # #= 2.5mm (clearance on each side)
4 - 2.5 # # = 1.5mm (interference on each side)

How does the bolt go though 1.5mm of steel? # :o :o :o

Smelly


smelly the calculation using 1/2ins(12.5mm)= 75-8(wall)=i.d.67-55(centre)=12-12.5(bolt)=2kg
MAMMER hey presto it fits

[Smelly]

Heyy Newchum,

Thanks for sticking with me mate!

Photos would be good.

Of course, I should have used 1/2in bolts in my calculation - not the damn hole size - sorry my mistake!

How did you get 12-12.5(bolt) = 2kg? :-/

[Smelly]

Now I have two(2) options - drill right through the drawbar or weld on a baseplate..


With the baseplate - I just wonder if 12.5mm of tapped thread x 4 holes is enough to secure the hitch under all that force/stress?

[Feral]

I would not be tapping threads into anything welded onto the trailer. They'll rust up and you will be stuck. Probably alright to "ease" the holes slightly in the coupling with a rat tail file to help with clearance of bolts to sides of draw bar, just dont go overboard!

One Idea might be to Just weld plates top and bottom, use bolts long enough to go through, nylock or splitwasher, your call on preference, either will do.

The other option is to use U bolts (preferably going right around draw bar rather than just the plate) with a top plate (welded on) only, but never seen that for a hitch so might be dodgy from an engineering point of view.

[Smelly]

THanks Feral - some more great ideas..

Feral - what are your thoughts of drilling holes into drawbar to make this thing fit?

ANd with welded plate - do u think 12.5mm of tapped thread x 4 is strong enough to hold the hitch under duress?

With regards to rust on the thread of hole - can't the thread be treated with anti corrosion stuff?

[Smelly]

I have hear that four(4) bolts going through the drawbar may not be strong enough as the drawbar walls can collapse/fold in - in this situation..is this true- if so, what is done to ensure this does nto happen? :-?

[HarryO]

Hey Smelly...

And all...

I presume you are fitting this coupling because you have
fitted cable brakes to this trailer?

If so, then the method that blackjack shows in his pics is the
ONLY WAY this should be done.

You must have this extra height so the brake lever assembly
can fit and operate successfully. (absent in his pics)

Harry.

[Smelly]

Wowwee! :o :o

Yes, I am fitting brakes - mechanical.

Why hasn't anyone mentioned this before then?

[Smelly]

Isnt strength compormised but with Blackjacks setup?

[HarryO]

Not at all...

Have fitted them this way for many years with no problems.

If you have a look at any new or original fittments, you will
see that they are also fitted this way.

I have towed my own boat on many trips over the years,
to remote areas, and over badly corrogated dirt roads, and
even tho the trailer has had the odd repair,
the coupling fittment has never needed attention.

The angle you use should be 100mm x 50mm x 6-8mm
thick. This part carries the load.

The RHS (40mm x 30mm x 3mm) is plenty strong enough.

Harry

[newchum]

Heyy Newchum,

Thanks for sticking with me mate!

Photos would be good.

Of course, I should have used 1/2in bolts in my calculation - not the damn hole size - sorry my mistake!

How did you get 12-12.5(bolt) = 2kg? # :-/
it was suposed to be=2kg HAMMER(help tap the bolts in)i will send you an email tomorow to show you my setup it is far easier and structurly sound no possibility of rhs collapseing

[Smelly]

I am keen to hear what others think of Harry O's opinion...please

You stated.. "You must have this extra height so the brake lever assembly can fit and operate successfully. .."

Just how high must the hitch off the drawbar?

I am connecting a 1.3m long steel rod (strating @ brake/hitch to just after the APEX in the trailer memebers) and then onto the cables. #THis rod is going underneath the drawbar..

Harry O' - the fact that I am going underneath drawbar, must I still raise my hitch so high (as per Blackjacks' photos)?


Smelly

[Smelly]

Harry - Why must the hitch be this high off the drawbar?

[Smelly]

Blackjack - why did you moun the hitch so high above your drawbar?

[HarryO]

Hi Smelly....

Do a dummy fit-up, and you will see.

Or go to a boatyard and have a sus and fiddle.

Harry.

[Smelly]

Thanks mate.

Can you advise why the hitch needs to be that high off the drawbar?

I am curious

[HarryO]

No worries...

Picture the coupling mounted flat on the drawbar,
and hold the brake lever up to it.

The contact point at the back of the (coupling) ram where it
pushes the lever will be too low, and the lever
wont be able to pivot, as the saddle of the
lever will be resting on top of the drawbar.

Can you picture it?

The "saddle" of the lever must be at least 30mm higher
than the top of the drawbar, so it can pivot,
and the coupling must be raised to match it.

Have a play with it and you will see it.

P.S. #The overall strength of this setup, or any other
setup, will depend on the condition of the steel, and,
of course, your welding skill.

Harry..

[FNQCairns]

Smelly if I understand correctly I had exactly the same problem when I built my trailer after much head scratching I fixed with another piece of steel welded to the top of the drawbar and of a thinner width which then .......will post a pic tommorrow it's pretty self explanitory and fairly simple also and I suspect very close to what Harry is talking about.

cheers fnq

[Smelly]

Thanks - look foraward to it..

Phew! :o :o

[Feral]

I have hear that four(4) bolts going through the drawbar may not be strong enough as the drawbar walls can collapse/fold in - in this situation..is this true- if so, what is done to ensure this does nto happen? :-?


This will only happen if king kong does up the bolts.
Remember a coupling is not supposed to have any more than about 120kg vertical load on it.

Personally I'd be using nuts, not threaded holes in the plate, yes you can treat the threads, yes it should be more than adequate for grip, but I have still had to many rust threads over the years to take the risk!

[Smelly]

Thanks Feral.

If I use fully welded plate, I am unable to use nuts because there is no clearance underneath the plate.

But if I go Blackjack's way, nuts will be the way to go.. :)

[Smelly]

Which option do u prefer Feral?

[FNQCairns]

Here you go Smelly hope it helps:

[Smellier]

Thanks .

Dims of bit in between baseplate and drawbar??

[FNQCairns]

Think it may be 30mm high, best do a dry run yourself with the base plate and measure to save any inconstancy's between brands and production, enough length to just swing a spanner underneath for the nuts. I used a 4.?mm section and consider it overbuilt for a 1500kg trailer.

cheers fnq

[Smellier]

Hi again.

I assume this bit in between is not solid but 4mm wall thickness?

[Smellier]

at the end, do i see the baseplate overlapping the saddle of
lever ? :-?

[FNQCairns]

Yeah 4mm something I forget, the baseplate and saddle (welded to) is one piece of the shelf.

cheers fnq

[newchum]

smelly, have emailed pics to your smellier address hope they help
i like to work with KISS principle ;D
rodney

[darrmun]

here's a couple of pics on my little trailer

[darrmun]

other side

[Smellier]

Thanks Rod. Great help :D

So , u use no baseplates at all..

[Smellier]

Thanks Darrmum.

Intersesting - Photo called "Other side" shows a bracket sticking out at the front - what is this for?

[Smellier]

Nermum,

The holes in your drawbar look like they have been torched out with a welder...why didnt you drill them?

[Smellier]

Check this one out - not mine incidently ;)

Notice bolts upside down - your thoughts on how these bolts are configured?

[darrmun]

mate the brackets are for my swing away drawbar extension

[Smelly]

Question to you all.

Is there any advantage of welding an angle iron at drawbar opening (end) and mounting the two front bolts of the hitch to the angle iron - instead of on the drawbar itself? ::)

Smelly

[SO70]

go and have a look at any Tinka or Redco trailer with brakes.
they are all done with the angle iron at the front and box section at the back.
simple and strong.
they have been doing it this way for years.
if it works for them it will work for you.

[Smelly]

OK -

Great I will do that.

[blaze]

mass produced is exactly that, built to a cost and very rarely using the best or strongest design priniples, just because a manufacturer uses a design does not mean its the best. For my money there is a better way than relying on a bit of 3mm RHS to support the rear bolts on a tow hitch.
To all that dont like threaded plate for a base plate if anti seize is used there will never be a problem, its all about dooing some maintance.
cheers
blaze

[HarryO]

G'Day Blaze,

and all.

I agree with you that just because manufacturers
do it a particular way, it's not necessarally the best way..

I was alerting Smelly to the fact that the coupling has to
be mounted higher than the drawbar, which to date,
no-one had mentioned.

Some kits have a base plate that the brake lever is
attatched to, and other kits require a hole to be drilled
horizontally thru the drawbar, so the bolt becomes the
axle on which the lever pivots on.

I think that as nearly all the manufacturers mount them
this way, pretty much says it all..

It is simple, and it is strong enough to do the job.

Keeps a bit of unnecessary weight off the drawbar too.

If the boat/ trailer is a larger, heavier combo,
say a 20'+ sharkie, or a 213 haines,etc, then a much
heavier mounting plate setup would be required..

Harry :)

[SO70]

if you dont like the size of the material used in a mass produced trailer then use the same set up with thicker material.
simple isn't it??

[Smelly]

Great points all.

I visited a boat shop today and walked around the yard...and looked at about 25 new boats..

Only 1 trailer had it hitch raised, the rest having the hitch mounted directly onto drawbar with many having front bolts into angle iron flush mounted (not raised) @ end of drawbar..

I want to clarify what I meant in my last addition..mounting front hitch bolts onto angle iron which is butted up flush (not raised) with front of drawbar with rear bolts going through drawbar without raised box channel...in other words - flush mounted to drawbar..

Still undecided which way to go because the raised design may create some operational constraints - lowering boat into water and ground height of hitch higher again if wanting to mount onto sedan - may have to jack rear of car up.. :-[

I also believe raising the hitch may relate to a handbrake design that needs it's hitch raised...Other handbrakes that are designed differently may not require the hitch to be raised....just thoughts... ::)

To summarise, here are my options..
1) Raised hitch
2) Flush mounted into drawbar (without any baseplates)
3) Bolt hitch into tapped holes of fully welded top baseplate
4) Bolt hitch through drawbar using both top and bottom baseplates
5) Bolt front of hitch to angle iron flush mounted at end of drawbar and rear bolts into drawbar (without raised box)

All interesting...which one?? ::)

And, while we are still keen, best way to attach safety chains..? welded or bolted? :-?

I know this is being flogged to death but is raising some excellent points about hitch mounts and will be used for future reference (search keywords) for the next person who wants to know everything about mounting their hitch..

Smelly

[Smelly]

Darrmum,

In your first photo, I notice an extra piece of flat at the front bolts - why?

ANd, why did you mount the hitch higher?

[FNQCairns]

Anchor chain bolted or welded is easy, bolted is flatout illegal.

The extra height above drawbar can be a minor problem on some low slung cars like our daily, on the patrol it is prefered.

cheers fnq

[HarryO]

Hey all...

When you looked at the trailers in the yards, did they
all have cable brakes?

If you look at the pic you posted where the bolts are
mounted upside down, you can see that the horizontal hole
drilled for the brake lever pivot is as low as allowable,
yet the coupling ram is still too low to operate as it was
designed to.

I would also suspect that the mounting bolts had half their
heads ground off in order to fit the coupling without fouling
the drawbar.

That alone would greatly increase the integrity of the mount..

NOT!

RE: chain.. FNQ is spot on, they MUST be welded.


Harry.

[darrmun]

needed the extra piece of flat to "shim it up " to allow for the swing away drawbar extension bracket

[darrmun]

oops my mistake that is the bracket the rear 1 is the shim

[newchum]

here are two hitches mounted on the draw bar. both still opperate the brake lever ok and no dodgy was done to make the bolts fit ,sorry about the quality it the result of a resize

[newchum]

number 2

[HarryO]

Good one, Newchum... ;)

There will always be exceptions.

Presuming, again, that Smelly bought his kit new,
and it is the style that has a baseplate, it should
still be mounted as per Blackjacks method.

The lever in his kit will have an clearance inside the
saddle of 55 odd mm. (to suit 50mm wide drawbar)

Clearly, some of the old styles were wider
(and custom made in most cases), as the
drawbar width would have to be at least 75mm wide
minimum to allow the coupling to be drilled and bolted
directly to it, and the saddle would have to be 80mm
wide inside to allow it to pivot freely.

Harry :)

[Smelly]

Thnaks guys.

You have all been a huge help.

I will let you knwo what I decided upon when I instlal it - hopefully late next week ... with photos:P

[Feral]

My draw bar is 100RHS, I dont have any issues with hitch mounting ;D