Trailer modifications / Small pulley wheels / Hydraulics

[wilbo666]

http://www.skf.com

Can be useful for finding bearings I find

e.g.
http://www.skf.com/portal/skf/home/p...&newlink=1_1_0

-->product tables --> search

I found some bearings with 9mm ID, 20mmOD (Would have to machine pulleys to fit), but they aren't very wide (6/7mm)... so you would need to further machine pulleys to have snap rings to locate bearings, and spacers to keep at correct height...

i.e. 619/9, or 61900...

Cheers
Wilbo

[hemi twofifteen turbo]

hmm didn't know the central section moved. Maybe a little bit of re-engineering is in order if you're snapping cables. Its difficult to see, but if the cable is anchored solidly to the bottom tray you could replace it with a pulley and loop the cable back up. see diagram. This will increase lifting force by X2, or in other words half stress on cable and winch. You could get a V belt idler puller off a car at the wreckers quite cheaply. ($5?)

http://www.freeimagehosting.net/imag...56e446a961.jpg

[oldcorollas]

bearings.. should be easy to machine pulley to larger size
nachi, twin sealed shields, 10mm inner, 22mm outer
http://www.nachi.com.au/pages/produc...?bno=6900-2NSE
etc

edit: bah, press button hours too late

anyway, if there are shield bearings and seal bearings... get the latter

[M.J.H]

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.

Probably be more expensive but why not have a look at some pulleys at the local boat supplies shop?
Have decent bearings, Can take a fair load and being on a boat they can handle water no problem.
maybe something like in the link below.
http://www.whitworths.com.au/main_it...AbsolutePage=1

[Slim]

. Its difficult to see, but if the cable is anchored solidly to the bottom tray you could replace it with a pulley and loop the cable back up. see diagram. This will increase lifting force by X2, or in other words half stress on cable and winch. You could get a V belt idler puller off a car at the wreckers quite cheaply. ($5?)

You can't halve the stress on the cable... just sections of the cable. ie: the front part of the cable near the winch will find it easier, but the other end of the cable is going be just as stressed out.

[hemi twofifteen turbo]

No it actually does halve the load on the cable. Since the load is divided over the equivilant of 2 cables now. There is a formula for it i've seen with sling lifts somewhere?

How hard is it to lift? How much do you think the bearings are likely to help? And how much easier would you like to make it? If it's just difficult now, with bearings it may improve by what 20% by a guess? Is this enough to suit?

Here is a pic of what i was trying to explain before, prob need to fullsize it to see what i've drawn on it.

[af300e]

If it's just difficult now, with bearings it may improve by what 20% by a guess?

20% is probably a pretty conservative estimate on improvment depending on how rubbish the current plain bearings are.
Remember there are 14 pulleys and if each has its drag reduced by even 2% the total drag reduce by almost 30%.

A friend of mine bought a dirt bike a couple of years ago and the rear suspension which includes 3 or 4 needle type bearings was so stiff that we assumed the shock shaft was bent. The application involves enormous leverage and this was why we suspected the shaft rather than the bearings.
As it turned out, only one of the bearings was badly rusted but even this was enough to prevent the swingarm moving more than about 30mm (total travel is around 270mm). When the bearing was loaded up it just seized up completely.
What I'm getting at is that we shouldn't underestimate the effect of bearing drag on the total load.

I'd estimate that a move to ball bearings will almost half the effort required to winch the trailer up and that would be a considerable improvment at a nominal cost.

It's hard to see in the original pics but how many pulleys does the cable run over at the actual lift end of the system? Could you take a closer better pic slim?
It looks like it might already have a system like the one Hemi has designed.

[Slim]

Here's a diagram that i just drew.... http://img81.imageshack.us/img81/275...diagramzi6.jpg
Description:
The 3 pulleys to the left of the diagram are located at the very rearmost part of the trailer (The lifting end of the tray).
Two of the horizontally oriented pulleys are located midway along and on the front part of the arm that the wheel is attached to (near the pivot point of the tray).
The last pulley is located centrally in line with the winch.

If i were to draw the full cable diagram it would be a mirror image of the one i drew with the centreline being through the pulley closest to the winch. The two centre pulleys share a common axle.


Note: If my memory/diagram is correct then there must be only 12 pulleys. I think it looks how i've drawn it, but i'm pretty sure i counted 7 pulleys per side. So i'll have to double check when i get home to see where the discrepancy is.

[Turdinator]

I found some bearings with 9mm ID, 20mmOD (Would have to machine pulleys to fit), but they aren't very wide (6/7mm)... so you would need to further machine pulleys to have snap rings to locate bearings, and spacers to keep at correct height...

i.e. 619/9, or 61900...

Cheers
Wilbo

These are fairly light duty bearings. Check there load capabilities befor using them. If you run them in pairs make sure you space them apart, as placing them side by side won't load the bearings equally and you won't get the benifit of a paired setup. The seals are usually pretty good on the bearing, just make sure they are full contact seals eg 2RS or LLU etc.

If you use a desent grease on the bushes it will make a HUGE difference. There are greases specifically designed for slow speed sliding bush applications. From memory dow corning make some good ones.

As for new pulleys with bearings in them, you will struggle to find them off the shelf that small. They are usually 80 - 90mm od with a 15 - 17mm bore.

If you go to CBC see Shane at Dandenong. He's pretty switched on. Or call me if you really get stuck.

[af300e]

Nice diagram. So in addition to the reduction in the winch, the pulley system also acts as a reduction. It looks quite nicely designed.

I agree on the 20mm OD bearings being light duty, I'd be tempted to use a 32mm OD 10mm ID sized bearing if the pulley dimensions allow.

Greasing the bushes is an excellent point, but sealed ball bearings are maintenance free.

[Slim]

It's the maintenance free part that i'm looking for. The trailer sits for months at a time unused so things are able seize up if grease is washed away or dries up. It took me quite a long time to get all the pulleys out, let alone clean and reassemble the whole thing (the wheels have to come off to get the rear pulleys out and two pulleys per side are unserviceable because they're on axles that are welded in. ). I'm anticipating the cables will be a PITA to get evenly balanced.

I think even quality grease will disappear too quickly. Also, the bushes and inner surfaces of the pulleys are all rough from corrosion so they'll never run smoothly withought being machined or something. A lot of the pulleys were stuck to their bushes and were turning on the bolt rather than spinning on the bush.

[love ke70]

it would seem theres a reason most of the other dolly trailers just have a couple of ramps

[Slim]

it would seem theres a reason most of the other dolly trailers just have a couple of ramps

Yeah, because the designers are lazy and couldn't think outside the square. The guy that designed my one was a true visionary. He had ideas. He made them happen.

You should see the number of chicks that flock to me whenever i pull up with my cable operated dolly trailer. They fucken can't get enough of that shit.

[The Real Roadrunner]

I agree on the 20mm OD bearings being light duty, I'd be tempted to use a 32mm OD 10mm ID sized bearing if the pulley dimensions allow.

Whilst a 20mm bearing with a 6-7mm thickness is fairly light duty what about using a double row angular contact bearing?

Should be something around in the correct size, like something with 3/4"od 3/8"id and 5/8" thickness. press them in and run a conical spacer underneath to ensure the pulley's don't rub on the chassis and robert's your father's brother.

Cheers
Linden

[Slim]

Whilst a 20mm bearing with a 6-7mm thickness is fairly light duty what about using a double row angular contact bearing?

Should be something around in the correct size, like something with 3/4"od 3/8"id and 5/8" thickness. press them in and run a conical spacer underneath to ensure the pulley's don't rub on the chassis and robert's your father's brother.

Cheers
Linden

huh? say what now?

I'm sure you're making sense, but i'm not familiar with some of the terms... "double row angular contact bearing"... and where does this "conical spacer" go?

I understand the bit about Uncle Bob. I'd prefer that you keep him out of this.