Trailer modifications / Small pulley wheels / Hydraulics

[Slim]

Hey guys... I've got this dolly type trailer that i primarily use to tow my mini around.



It's got a fancy design that allows the tray part to squat to sit on the ground which allows the car to be loaded easily without ramps. (see pic below... you can sort of get an idea of how it squats). It uses a bunch of pulleys and cables to raise and lower the tray. The main winch is what you use to put tension on the cables.

In this pic, if the blocks of wood weren't there, the tray would lower to sit on the ground.



Now, the problems i'm having is that the trailer uses 14 pulleys that have plain bushes. This design makes keeping them lubricated and free spinning difficult and time consuming. It has always been very stiff to operate and i think that i should be able to vastly improve its operation by replacing the pulleys with ones that incorperate a bearing of some type.

Here's a close up of a couple of the pulleys. The other main ones are near the wheels.





Any new pulleys can't be bigger in overall diameter or thickness or the trailer will need substantial modifications to make them fit. Could a bearing be put within the existing pulleys?


My other more elaborate idea would be to fit two hydraulic rams, one on each side near the wheels, to raise and lower the tray (see mad photochop below). The hydraulic rams would be easy to keep clean and away from the elements by use of rubber boots etc.



The only problem i can foresee, and it's a big one, is that the two sides may not raise at the same speed which would result in the tray being skewed, jammed, or damaged.

If i decided to do this design, how would i go about making sure that the two sides would self balance. Is there a standard mechanism/design for this type of problem? I'm sure it's a regularly encountered problem with hydraulics.

[PlacentaJuan]

they would self balance because fluid can not put more pressure into one ram than the other (assuming they were running off the same pressure source ie hand pump)

sounds like your going to a lot of effort, wouldnt it not be easyer just to give the bushes a spray with liquid wrench (or wd40 etc but liquid wrench is better) before each use?

[legend]

i d use some anti sieze copper coat on them after a good clean up on them

[Slim]

they would self balance because fluid can not put more pressure into one ram than the other (assuming they were running off the same pressure source ie hand pump)

The pressure going in to each piston would be the same but if the resistance on one side is greater (ie: if the car is off centre or something is a bit stiff to move) then the result would be one side moves more than the other.

[Slim]

Sounds like your going to a lot of effort, wouldnt it not be easyer just to give the bushes a spray with liquid wrench (or wd40 etc but liquid wrench is better) before each use?

Yeah, i'm just exploring all options at this stage. The thing is that i've never seen it work really well. I reckon there must be improvements to be made.

The pulleys themselves are not siezed... it's just that as soon as pressure is applied the amount of friction between the bush and bearing becomes immense. The first few pulleys are taking some pretty hefty loads due to the way it's set up. A spray of liquid wrench will do sfa.

[Jt_70R]

you could always try using some low friction polyurethane in place of the plain bearings. try something like 'oilamid' or 'austlon' (trade names).

give CBC a call and speak to one of their tech people, they are normally pretty helpful if you give them the full details of the application.

[hemi twofifteen turbo]

put a 12v power winch on it. Then who cares how hard it is to winch. Combine it with some of the other friction reduction options people have suggested here are your done.

The other option is buy or build 2 lighweight aluminum ramps. 30 seconds to pull out, light weight and simple.

If you really want to go the hydraulic ram, it would have to be power pumped as it would be time consuming compared to the other options. Having it power pumped gets complex, expensive and a bit overboard.

Also about the equal extension ram issue, -- simply brace the rear section so it is rigid. Then once one ram lifts higher it's begins to be lifting the car by itself (the other ram is just sitting there, hence that ram is carrying more than 50% of the load so it req's more pressure to extend, the other ram then becomes the easy path for the fluid, so in effect it levels itself out by itself. If you park the car relativly centrally I really doubt you'd have a problem at all. Otherwise run one single ram in the middle etc etc.. just rambling now ...

But really just buy a 12v power winch off ebay and be done with it.

[love ke70]

why not take the pulleys into your local bearing specialist and lay it out on the table, they will fix you up with some good bearings for the job and nearly always have something that will suit.

[Slim]

you could always try using some low friction polyurethane in place of the plain bearings. try something like 'oilamid' or 'austlon' (trade names).

give CBC a call and speak to one of their tech people, they are normally pretty helpful if you give them the full details of the application.

I'll take a look at those products and CBC or similar bearing shops were gonna be my next port of call... but being a Sunday i thought i'd ask the Toymods masses first.

put a 12v power winch on it. Then who cares how hard it is to winch. Combine it with some of the other friction reduction options people have suggested here are your done.

I was going to buy one of them anyway... but i recently snapped a cable so it sort of does matter how hard it is to pull. The cables aren't invincible.

The other option is buy or build 2 lighweight aluminum ramps. 30 seconds to pull out, light weight and simple.

This option is a possible solution but i'm going to stick with the squatting design because i think it's awesome. A lot of the other dolly trailers have ramps but i bought this one because i liked the unique design.

Also about the equal extension ram issue, -- simply brace the rear section so it is rigid. Then once one ram lifts higher it's begins to be lifting the car by itself (the other ram is just sitting there, hence that ram is carrying more than 50% of the load so it req's more pressure to extend, the other ram then becomes the easy path for the fluid, so in effect it levels itself out by itself. If you park the car relativly centrally I really doubt you'd have a problem at all. Otherwise run one single ram in the middle etc etc.. just rambling now ...

I'm not sure which bit you're suggesting i "simply brace". The swing arms that the wheels are attached to are independent of each other... they can't really be attached together in any feasable manner. There's really not much to brace to anything... it's a bunch of independantly moving parts. You realise that the centre part also is a turntable that rotates when the car is towed around tight corners? That rules out screwing about with things in the centre part, especially since there is limited clearance under a car.

But really just buy a 12v power winch off ebay and be done with it.

Probably will do that... or buy a manual one with a few reduction gears.

Sorry to sound like i'm slamming your ideas. I appreciate all those that offer suggestions. I'm aware that you can't really get a full understanding of the way it's constructed by a couple of shoddy photos.

[af300e]

I'm happy to give you a hand with machining if you can't find a bearing that suits.

Replacing the plain bearings with ball races is probably going to be the cheapest and easiest way. Something like a spigot bearing might suit.

[Slim]

Thanks for the offer Andrew.

I think i will be looking into replacing the pulley wheels with ones that will accept a bearing. It does seem like the easiest way to fix it.... however it's still not gonna be all that cheap to buy 14 pulley wheels and bearings.

How sealed are sealed bearings? Can i rely on them to not let any water in, even if they're sometimes sitting in it? I'm just a bit worried about the pulleys that are orientated horizontally on the front part. When it rains, they're going to be copping a fair bit of water.

[love ke70]

do you ever see grease coming out of them?
my understanding is, theyre pretty sealed.
surely you will be able to replace just the bearings on most and press them into your pulleys? even if you have to machine the ID of the pulley a little bit to fit a different bearing?

[af300e]

^^^^Sealed bearings are pretty sealed.
The wheel bearings in my dirt bike cop an absolute flogging across rocks, tree roots etc, often at 100km/h and are often submerged whilst rotating during river crossings.

That they last around 2500km in these sorts of conditions boggles the mind.
Just buy a decent brand and make sure that the size is nice and common. That should keep the cost down.

I don't know if I'd bother replacing the actual pulleys if you don't have to. I'd imagine that pulleys will be dear compared to bearings.

Unless you can find something off a common car at the self wreck..............?

[love ke70]

bit like sealed wheel bearings in a diff, in my 4wd, theyll spin through cement like mud, sand, and dust, and they have never given me a problem.
so yeah, id say theyll be safe

[Slim]

^^^^Sealed bearings are pretty sealed.
The wheel bearings in my dirt bike cop an absolute flogging across rocks, tree roots etc, often at 100km/h and are often submerged whilst rotating during river crossings.

That they last around 2500km in these sorts of conditions boggles the mind.
Just buy a decent brand and make sure that the size is nice and common. That should keep the cost down.

I don't know if I'd bother replacing the actual pulleys if you don't have to. I'd imagine that pulleys will be dear compared to bearings.

Unless you can find something off a common car at the self wreck..............?

A couple of the pulleys have seen better days. I will investigate whether i can buy some to match the existing ones or maybe look at repairing the couple that have sustained damage. God knows how they got so beaten up.