28 March 1997


That bit following the tractor finally gets a look in as

Ken Wootton Trailers passes timely maintenance tips to Andrew Pearce

THESE days the seasons seem to swing by faster than the sails on a windmill, and in the rush to get on with the next job the farms trailers always seem to be forgotten.

But the rustle of growing grass means their busy time is starting again, so why not use the next wet spell to give the fleet a springtime service?

You will be taking out one variable from the silage-making equation, giving the tractors brakes an easier life and potentially making the roads a safer place, so it has to be worth the time invested.

Following a logical sequence makes sure nothing is missed, says Ken Wootton. If you are looking over a trailer before the silage sides go on, start at the bottom and work up. If they are on already, have someone watch while you tip the trailer slowly to check gate operation and the rams. If there has been a hiccup in fitting, a second pair of eyes should save bending or breaking something.

The check-over process is straightforward enough, and the following pictures fill in detail. Only one thing needs to be stressed – when working under a raised trailer, prop the body up. Never rely on just the hydraulics; some who have are not here to tell the tale.

1. Most know that using the right tyre pressure is central to puncture resistance and wear, but still do not bother to set them accurately or change them to suit the job. The trailer makers sticker (should it still exist) shows the right pressure to handle maximum load. Unless grass is wet it weighs lighter, so there may well be scope for dropping pressures to give the soil an easier time, especially where journeys are short and speeds low.

2. A dry time puts high shock loading into wheel bearings, so they need to be fighting fit. With axle jacked up, rock the wheel at top and bottom to find play. Pop off the hub dust cap, pull the lock pin and adjust bearings until just a trace of play is left. Half-fill the cap with grease and tap it back on – do not overdo the filling, or grease will squeeze past the hub rear seal and get on to the brake linings.

3. If the trailer has plodded about in mud over winter, pull off all brake drums and clean everything out. Brake shoes must have good lining thickness left; change them if they are under 3mm as hard work is ahead.

4. Pop the drums back on and adjust each brake. This ones adjuster is the angled bolt below the hydraulic line (right). If you have not had the drum off and the adjuster runs out of travel, it is telling you the shoes are shot. With all brakes cleaned and adjusted, couple-up a tractor and have someone try them. Watch the ram and pipework for leaks, and see that all return springs do their job swiftly as pedal pressure is released. If not, the linkage is binding and needs to be stripped/greased. Any leaky ram needs resealing or changing. It is worth comparing prices; a replacement is likely to last longer and fitting it is faster.

5. The trailer brake coupling must be sound – change it if it leaks. Chafed rubber on the brake hose is no problem as long as the underlying braid is OK.

6. Wheel nuts need to be tight. If you have no big torque wrench – and who has? – wind them up hard. Re-check all nuts through the first days work, as they will probably settle and loosen under load.

7. Tandem axle pivots wear in time. Some need greasing, some do not – look for nipples. Check pivots individually by jacking the trailer chassis and seeing how soon the axle follows. Some makers bush the pivots, some do not. Although it may be a pain, change bushes before wear goes too far or the underlying steelwork will suffer and a new bush flop about. Wear in unbushed systems generally involves changing brackets. While you are around the axle, see spring-to-axle U-bolts are tight.

8. Two things matter about drawbar couplings – wear around the eye itself, and the state of the tractor hitch. As the eye loses thickness so the downward load it can handle decreases. A new EN16 eye plate accommodates 6t, so one half worn can only deal with 3t. As for most trailers the download is roughly equal to empty trailer weight, the strength margin of a worn eye can be small. When replacing, cut off the old one completely and weld the new version to clean drawbar steel. Unless you have the right rods and the know-how, a plate-to-plate joint can turn out dangerously brittle. Check the tractor hitch by coupling the trailer then jacking under the drawbar. The gap between hitch hook and hitch plate should be 10mm or less, and the drawbar eye must stand no chance of pulling through it. If the gap is too big, sort out the hitch lift rods and retaining hooks.

9. Worn trailer body pivots can be tricky when tipping. Check by levering between the chassis and body, and re-bush/replace as necessary. Pin retainers (R-clip, split pin or whatever) need to be present and correct.

10. Hydraulic oil does not improve silage quality, so check ram seals and pipes by lifting the trailer to maximum and briefly holding it there. Fixing leaks before the season starts will save grief later.

11. (right) Silage sides are well up in the air and subject to a lot of flex. To minimise the chance of cracking, use bolts of the right size with decent washers under the head and nut. Using locknuts keeps them tight.

12. Sort out any frayed door cables or fix wear in pull bar pivots. Repaired cable must be the same length as the original. Lift trailer slowly to see door goes up square; if not, adjust operating bits so it does.

13.Last but not least fix the lights. Start at the seven-pin plug; have it apart and check connections. Follow the cable back and fix any breaks, then repair/replace any duff light unit. A little Vaseline on the bulb cap and contacts helps delay corrosion.