Paging the trailer towers (behind cars with bikes on them, not behind bikes)

I think my trusty Tarn 3 bike trailer needs some TLC. It is a testament
to the longevity of hot dip galvanised chassis and alloy 'runners', that
if it was a bike it would have made it eligible for the VMCC for the
last 5 years. Champ seemed unimpressed by this at Prescott a couple of
years ago, but it justifies what I paid for it back in Manx Millennium
year.

After 30 years of use, though it has begun to 'thrumble' in a
disconcerting way at motorway speeds (not saying exactly what, but on
autoroutes you can 'drive through it').

At first I thought it was wear on the tow hitch (because it was worn),
and a new tight fitting one (too tight in some ways) has helped. The
taper roller wheel bearings seem OK. I repack them with grease and
adjust them (just perceptible rim rock) each spring, and they spin
smoothly, though TBF one is a tiny tad rumbly I suppose. Possibly a
really badly out of balance wheel, and I must do some primitive checks
to eliminate that.

But I am also wondering if it could be knackered 'indespension' units
giving some fore and aft play IYSWIM.

As a 30th birthday pressie I could treat it to new ones (complete with
new bearings) as it doesn't owe me much otherwise, except for tyres (and
lighting boards).

BTW, for those of you with canbus electrics cars and towing attachments
two tips:

1) If you manage to plug in a manky old lighting board socket upside
down (don't ask), pay attention to the strange combination of lights and
accompanying strangled noise from the flasher relay beeper. Unplug
rapidly before it blows the fuse (eventually traced to the one supplying
the rear 12v auxiliary socket.

2) If you don't heed tip 1 and despite plugging in a known good lighting
board the right way up, after replacing the blown fuse, find you gave no
brake lights on the trailer - all is not necessarily lost. Take it back
to the place that fitted the kit (not the supplying main dealer in my
case). If they are a salt of the black country earth, man and lad in a
shack setup, they may suck their teeth, and then swap the connections to
use the 'spare' relay on the control box. This is used for reversing
lights on twin socket or 13 pin socket set ups. As mine is only a pikey
single 7 pin job I have no need of it. So that's 2 quid for a pint of
Bathams instead of 25 quid for a new unit plus labour to remake all the
connections.


--
+----------------------------------------------------------------+
| Pete Fisher at Home: |
| Voxan Roadster Gilera Nordwest * 2 Yamaha WR250Z |
| Gilera GFR * 2 Moto Morini 2C/375 Morini 350 "Forgotten Error" |
+----------------------------------------------------------------+

 

Mine "thrums" at ~70mph, just to remind me I should really be doing
60. It's wheel balance, since the tyres have worn a bit. The
bearings are the same as yours, but their thrum is at lower speeds and
you can tell as it comes and goes with cornering, especially when
loaded. The higher-speed thrum lessens considerably when loaded,
otoh, when there's more load on the wheels.

I'm not convinced that they do that, you know. I think they just jack
it in, catastrophically.

 

You've not seen mine. It's shit. Really shit. But it works.

Best place for *everything* trailer related is here:
http://www.towsure.com/category/6396-_Trailer_Parts

You could build your own from the parts book!

 

In communiqué

Indeed. There is a branch not far away. I think Pip may have confirmed
what the problem is likely to be though. I'll get it up on axle stands
and see if one of the wheels keeps stopping in the same place after a
gentle spin.

--
+----------------------------------------------------------------+
| Pete Fisher at Home: |
| Voxan Roadster Gilera Nordwest * 2 Yamaha WR250Z |
| Gilera GFR * 2 Moto Morini 2C/375 Morini 350 "Forgotten Error" |
+----------------------------------------------------------------+

 

Very logical. I'll do some rough and ready balance checks.

Well TBH I only have a vague idea how they work. The blanking off ends
of the square box section bit that presumably holds the rubber torsion
thingy has rusted away (the only bits that have) and I wondered if the
rubber may have perished. But as you say, they probably twang like
knicker elastic and go completely FUBAR.





--
+----------------------------------------------------------------+
| Pete Fisher at Home: |
| Voxan Roadster Gilera Nordwest * 2 Yamaha WR250Z |
| Gilera GFR * 2 Moto Morini 2C/375 Morini 350 "Forgotten Error" |
+----------------------------------------------------------------+

 

indispension units are simple, 2 bits of square section steel (outer housing
which welds/bolts to the trailer, inner bit with the swing arm on it,
inserted 45 degrees offset), 4 rubber inserts, and not a lot else.

i guess over time they are bound to wear the rubber inserts away, and when
that happens i would guess the swing arm bit can move a bit too much on the
housing, wouldent take much to allow the suspension arm to oscilate as you
go down the road.

personaly, i'd just spunk down the dosh for a pair of new suspension units,
think i paid around 60 quid for a pair of 450 kilo rated ones when i built
my motorcycle trailer a few years ago, you get the hubs and thus new
bearings as well, and in one go you've replaced 80% of the moving parts on
the trailer.

just depends if they are bolted on or welded on to how much of a bitch they
are to change out.

 

In communiqué <>, gazz

That was my theory. No obvious sign of free play though,

Six bolts on each. I might soak them in plusgas in anticipation of
dismantling, but a very crude test suggests that one wheel is
significantly out of balance. I think I'll get both re-balanced at a
tyre bay first and take it from there.


--
+----------------------------------------------------------------+
| Pete Fisher at Home: |
| Voxan Roadster Gilera Nordwest * 2 Yamaha WR250Z |
| Gilera GFR * 2 Moto Morini 2C/375 Morini 350 "Forgotten Error" |
+----------------------------------------------------------------+

 

Like all Metalastic type things, they fail eventually by separation of
the rubber from the steel. Indespension *may* have incorporated a
retention flange or something similar to prevent the moving element or
complete bush parting company from the mounting tube, but I don't recall
so.

 

Without nipping outside to look, ISTR that the inner box section & the
outer one are simply held together by flanges that are pressed onto
one of the box sections. IIRC the rubber isn't bonded to the metal at
all: it consists of four rubber cylinders that are shrunk by freezing
using something like liquid nitrogen, then simply inserted from one
end. As they warm up, they expand and that provides the suspension
pre-load and retention grip. It was on the telly so it must be true.

 

Perhaps it was an earlier design or some other make, then. I distinctly
recall the design I mention, and thought it a bit iffy.

 

Well the TV prog in question was a long time ago, so wibble.