Ping rubber specialists.

Hi all,
I have recently acquired a galvanised dingy trailer that is 1) fairly old and 2) has probably sat with way over the design weight on it for many years [1], and so the 4 (x2) rubber rods that make up the 'independent suspension' have been over-compressed / distorted and so 3) the ride height has been compromised (tyres very close to the inside of the mudguards) and 4) the 'suspension' (ride / travel) has also been compromised.
I don't think it's likely to catastrophically fail / collapse as it looks like the rubbers just get squashed flat(er), however, it's not ideal. This sort of thing:
http://i63.tinypic.com/11vgoe1.jpg
Now, in many cases these suspension units are independent (of the trailer chassis) and so can be replaced easily. In this case they are part of the actual chassis and so not so easy to replace.
(If I was to replace them I would have to first remove the old units and then grind back the galv, then weld plates to the underside of the box section to allow fitment of standard independent units and re protect with cold galv etc).
Now, assuming I could get the old arms out of the box section (drill, Porta Press) and could find the right rubber (section, material, elasticity) I could (hypothetically) press the arms with new rubbers back in.
However, I'm not sure that is how they make them, or how some make them new and I think I read somewhere that they might first stretch the rubber rods (reducing the section), then they are frozen (temporarily 'locking' the reduced section) and then the rods and arm inserted into the tube where the rods then defrost, regain their full section and hold the arm in place. ;-)
An alternative thought was that years ago a mate had a large tub of some (nasty) liquid that he dropped some of my hardened rubber bits into (4 motorcycle carb inlet rubbers) for a few seconds, pulled them out and rinsed them off and they were all rubbery again? ;-) Anyone know what that liquid might have been?
A final / compromise solution would be to fabricate some sort of adapter that would both bolt onto the original trailer axle and then allow the new suspension units to bolt onto that, saving the issue of having to extract the old suspension stuff (I can just cut the old arm off) and remove the galv to weld etc.
As an aside to the main question I would be looking for what they refer to as '200kg units' (so 100kg each) because the trailer gross weight is 180kg and as a typical 14' (or less) boat that I might have on their weighs between 50-100kg, I don't want the suspension to stiff (been there before). You can easily buy 200kg units bit not with such a good range of designs (and so 'rides') as the heavier units.
Cheers, T i m
[1] There has been a 14' dinghy sitting on the trailer for ~11 years that I know of and the boat itself weighs about 75kg. However, with all the other bits that were left in there it could have been nearer 100. The real issue though is for some of that time the boat also had quite a bit of water in it, possibly at least 1/2 a cubic metre and so that was an *additional* ~500kg sitting on the suspension units! ;-(
p.s. I wonder now the trailer is unloaded the suspension rubbers might recover to some degree (over the next 11+ years), and if that could be improved if I was to apply some negative pressure to the units?
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T i m wrote:

Youtube implies soaking for a couple of days in isopropyl alcohol 3:1 with wintergreen oil
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wrote:

Thanks for that Andy, I did check Youtube to see if anyone had replaced such rubbers but couldn't see anything ... but didn't look for any 'revival' tips.
Do you still have the link to the so I can see the context please? Obviously there are safety implications if I was to do something and it made matters worse etc.
Cheers, T i m
p.s. Your reply does remind me I once bought some stuff that was supposed to be for conditioning catapult rubbers but I wasn't sure if it also 'revived' tired rubbers (and they would be cheap and easy to replace in any case etc).
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<snip> >Do you still have the link to the so I can see the context please?

I've since found this which seems reasonably 'scientific' (considering etc).

https://www.youtube.com/watch?v=EnGsllKvheQ

The bits of specific interest to me being how long any softening lasted and how 'easy' and cost effective it might be to apply any such process to my trailer parts.
Cheers, T i m
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T i m wrote:

This one was at least methodical about trying various liquids
<
https://www.youtube.com/watch?v=EnGsllKvheQ

Many others if you search youtube for "soften rubber" but the various brake/transmission fluids seem to risk swelling it.
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wrote:

Ah, yes, as you may see sometime I found that one after you mentioned Youtube and agree it was go re how the actual tests were applied and how he even left them to see how they felt a good time after.

It looks like the Isopropyl Alcohol / Wintergreen combo seems to be used fairly commonly and with good result, including any swellings going down (oooh, missus). ;-)
Cheers, T i m
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On 09/05/2018 11:00, Andy Burns wrote:

I've seen rubber expand, as it happens when I didn't want it to, when exposed to oil- specifically the oil used to fill a compass. I assume a cheaper oil with the same 'base' would work.
My concern in your application would be controlling the result- you don't want a trailer that is going to 'bunny hop' as you tow it and there is the question of load bearing.
While it seems like more hassle, I think total replacement is the safe option.
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On 09/05/2018 15:53, Brian Reay wrote:

Perhaps in this case the swelling caused by mineral oil would not matter so much (as there is plenty of space).

Agreed, both good points

Me too.
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On Wed, 9 May 2018 16:23:17 +0100, newshound

I also agree with having concern re the last point but I'm not sure about the first?
I bought a nearly new second hand light general goods trailer (the sort of thing you take your rubbish to the dump with) and empty, unless you took every speed hump at 2 mph, all you could see in the rear view mirror was the trailer in the air?
I also fitted the lightest suspension units I could find at the time to my previous boat trailer and that too was 'very lively', even when we loaded the boat down with general luggage / camping gear etc. So, my point (from experience) is that it's more likely to get a /bunny hopping' trailer by using the wrong suspension units (and not just the nominal capacity) than I might from just freshening up the old rubbers?

Also agreed, assuming I can achieve that without compromising the longevity of the trailer (how easy would it be to re hot galv the affected parts after welding the new parts on) and me finding the right spec units etc?
And remember, not all of us have unlimited budgets for such things? ;-)
Cheers, T i m
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On 09/05/2018 16:55, T i m wrote:

The difference between entry level trailers and car suspension is that the former don't have any proper damping, or even much friction.
With a heavy and attached load like a boat, you may not need much damping. On a tip trip, light and unsecured items may well levitate all the time.
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On Wednesday, 9 May 2018 22:35:54 UTC+1, newshound wrote:

Rubber provides damping, as it does in rubber car suspension such as the mi ni. That's one of the major reasons why it's used on trailers, though not t he only one.
There is one key difference between car & trailer: cars are heavy unloaded, loading full only adds somewhere around 50% total weight. Trailers OTOH ha ve no engine, drive train, top or crash safety concerns, so are very much l ighter, giving a much larger ratio of full to empty weight. That's not so e asy for a crude suspension system to deal well with.
NT
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On 09/05/2018 22:44, snipped-for-privacy@gmail.com wrote:

True, rubber does provide *some* damping, but original Minis had traditional hydraulic dampers. Later BL stuff had hydrolastic suspension with a lot of rubber in them instead of metal springs, but the damping was mainly provided by the flow of "water" through the connecting pipes. That said, what you say about the difficulty of optimising for trailers is exactly right. Although hydraulic dampers would make them perform better.
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On 09/05/2018 22:44, snipped-for-privacy@gmail.com wrote:

Are you suggesting Minis didn't need dampers?
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On Wednesday, 9 May 2018 23:17:44 UTC+1, Fredxx wrote:

no
NT
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On Wed, 9 May 2018 22:35:52 +0100, newshound

True, however, there does seem to be quite a bit of damping in the basic rubber / torsion suspension as I rarely see one oscillating on the road, even at speed. In fact I've seen many un damped car wheels and wonder why MOT's don't check them? [1]

Not all boats are heavy, the one I towed the other day was actually designed to be roof topable at 75kg, so attached or otherwise it would be the lack of suspension travel and compliance that would cause it to 'jump' (because of a bump or hole etc, not on it's own and never with any oscillation).

True, but not because of poor / no damping but because of under compliant suspension and / or a massive difference between the loaded and unloaded weight (or as you say, 'light objects' = no real load).
As mentioned elsewhere, the trailer I tow behind my motorbike has very light suspension because the maximum load is only the same as the weight of the trailer and that's mostly limited by the weight of the towing vehicle itself. Because it doesn't use any torsion but just rubber in compression, it does have dampers to keep things under control.
The 1/2 tonne trailer I built over 40 years ago has MM wheels (on Indespension units) and is reasonably heavy itself and so is fairly well behaved even when empty. Similar with the little steel framed with wooden panels trailer I made for my BIL (that even has a drop down tailgate and wheels allowing it to be rolled when stood on it's end, so it can be rolled sideways down a narrow side access. ;-)
The BOB Yak trailer that we tow behind the cycles doesn't have any suspension at all and will only bounce with any sort of load in it when it hits a rock. ;-)
We currently have 10 trailers but we do need to sell some. ;-)
Cheers, T i m
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If this were me, I'd have looked into your last option first i.e. a stainless steel plate on top and bottom of, and bolted across the axle/chassis and new indespension units bolted on. Are you sure the inside of the axle is well galvanised and not going to burst?
FWIW our 3 ton boat was towed from N. Wales to Southampton on its trailer one day last weekend. The trip went extremely well.
PS if anyone near Wirral wants a GP14 as a big project, I'm hoping to pull it out of our front "hedge" on its trailer sometime soon. We are in a smoke free zone, so it will probably have to be freecycled.
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Hmm, if you are talking a straight 'sandwich' mount here I'm not sure if it would keep good alignment (SS being quite slippery n all) or certainly without it being some sort of channel or even having an angle between the suspension unit and chassis tube to maintain some sort of trans alignment (tracking etc).
OOI, the axle tube is 40 x 40 box and could be 3+mm thick (I can't easily get to the end of it but will try tomorrow). The hole centres across the axle are 79mm so if using an M8 bolt with a 13mm AF nut that leaves:
79 - 40 -2 x 6.5 (half 13) = 26mm (13mm each side) of play room between the nuts and the axle. So, If I was to weld two lengths of 40 x 40 x even 3mm angle on top of the mounting plate (to form two guides or a channel running front and back of the axle) and then bolting them (so interference fit 'shouldered bolts') though and also a couple of countersunk screws up from underneath the plate and into a strip with captive nuts inside the axle tube at each end, that should give me something rigid and stable to bolt the suspension to and wouldn't need any welding and I could even get hot galvanised before fitting (as long as I allow for it etc. Or even one heaver strip on the front (then I won't have to allow for the galv) as because the wheel trails the axle there is only a turning moment in one direction so the strength might be best in the front where the bolts will be in tension.

Good point Bill, until I get the old rubbers and suspension boss out I won't be able to tell.

Excellent (I bet it was still a relief when you got home though)?
We towed the Leisure 17 from Sth Wales to Nth London and that was a twin bilge keep jobby so standing fairly high ... whilst not having much weight in the keels. ;-(

Hmm, 14' trailer you say ... ;-)

I wonder if the club I gave the 14' Skipper to recently needs 'project boats' for any of their school groups?
I'd happily come and get it if the trailer was good enough to get it and the boat back home safely?
Cheers, T i m
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Ours is one long keel on top of the iron casting, so it's the adjustable props that were my worry, but they were OK. I only did part of the journey, son did the rest in a Transit.

It's not worth coming any distance for, I'm afraid. The trailer is just two galvanised scaffold poles in a V shape with an axle bolted across at the appropriate place. The tyres are flat. The piggy-back launching trolley is a smaller axle that takes a U-shaped piece of conduit as its "handle". The conduit has rusted away, of course. All very primitive, but it always worked very well.
The GP itself is in a bad way, as the cover fell apart some years ago and it has been open to the weather. The mast prop has gone through the bottom, and I don't know whether it is just through the plywood or more structural parts. It's in a very deep holly hedge which is why I can't get at it easily.
Having said all that, it's probably only back to the state it was in when we were given it almost 40 years ago. We still have photos of very young son standing through the bottom of the upside down hull.
Ideally, I'd like it to go to someone locally who wanted a challenge to take on with their children.
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<snip> >>I'd happily come and get it if the trailer was good enough to get it

Ah.

Wooden boats can work on the 2CV principal. 1st the top leaks, then it fills up with water, then the bottom rots and it then becomes a self draining solution. ;-)
Not quite so good on the kitcar. The windscreen rubber has shrunk slightly and so now leaks in heavy rain. Foot wells are fibreglass and need bailing out now and again. ;-)

Shame.

Ouch.

;-)

Do many children have the patience for such things these days?
It was quite nice 'supervising' our daughter remove and clean the (4) carbs on her Suzuki 600 bandit today. Like me she resigns herself to accepting these things will take the time they take and trying to go faster is more likely to end with something broken or someone hurt.
The good news was after 6 hours (that included me going out and recovering my Mrs and a neighbour and her mobility scooter that just broke down a mile from home. A quick check over before throwing it and them in the car showed the electronic controller partly filled with water!) was that the bike seems to be running well again. Nothing worse than going though all that effort for no positive result (other than ticking another box in the diagnosis process and the experience etc).
I hope you do find a good home for the boat though Bill. ;-)
Cheers, T i m
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Same here, or some chemical cleaners etc.

Agreed (if by work that's what you wanted but in my case it isn't really).

I can't see it doing that though as I doubt I'd ever get the rubber as 'elastic' as it was from new?

Unless whatever I do reduces the overall strength of the rubber or dissolves it away completely I think the worst case situation here is that it just has no suspension. Now *that* when you will see a trailer bouncing all over the place, especially when unloaded.
And that's the very thing I'm trying to avoid by *not* fitting some aftermarket suspension unit that was actually too stiff.

I agree (re safety and assuming I remove enough of the galv to get a good weld (and not poison myself at the same time)) but ironically, any 'replacement' will also 'modify' the trailer, opening up other issues etc.
The 'best' solution (to / for me anyway) is to come up with a 'bolt up' solution, potentially including some fabrication etc but even little things like keeping enough room around the suspension plate mounting holes to get a spanner round the nut can be quite tricky.
eg. Image a 50mm box section axle tube, currently filled at the ends with this original suspension solution. Remove the old stuff and get a 200kg replacement that generally comes with a 4 hole mounting plate.
You can also buy matching plates you would typically weld under the chassis / axle but that would mean removing the galv (and partly why I considered the trailer in the first place).
So, if I was to make up a heavier duty plate to take the new suspension (say 6 rather than 3mm) and bond [1] and bolt it up from underneath using countersunk machine screws into a plate that can be slipped into the tube with welded on nuts, I wouldn't have to do any welding.
Ideally I would also use some angle between the plate and the front and back of the axle tube but I don't think there is the room for that and the nuts that secure the suspension unit to the plate? ;-(
I'll have to do some measurements ... ;-)
Cheers, T i m
[1] My mechanic mate has a 'gun' of some very strong (nozzle mixed, two part) glue that you use for bonding car / body parts together. Apparently such is acceptable now in place of weld (on the body particularly) for MOT's et (and many vehicles (inc boats and planes) are bonded together)?
I would be using it as 'belt and braces' over my machine screws. ;-)
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