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Post by bazza44 on Dec 2, 2023 7:30:52 GMT 10
I guess Murphy must have left OT's place and travelled to yours. What a senior moment that was, send Murphy on his way.
Barry
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Post by jr on Dec 3, 2023 18:53:16 GMT 10
Spent a couple of hours measuring and drawing the new AL-KO brakes. I have never been able to find out where the magnet should be located in relation to the drum surface it runs on. I expect most of the magnet should be supported on the square shaft it is mounted on, but this means that the magnet is always rubbing on the drum to a far extent with a light spring pushing it on. One way to check magnet to drum spacing is remove both drum and brake backing plate then put the drum with bearings back on the axle and measure the distance between the drum magnet running surface and the brake mount plate welded to the axle. This will give you the correct distance between mount plate and drum magnet running surface. Subtract the brake shoe mounting plate thickness from that distance you measured above. Now remove the drum and mount the brake backing plate and measure from front of magnet to brake shoe backing plate surface using the distance you calculated above and see how much of the magnet bearing surface is being used. I found that using the special spacer to allow for my old Melbourne Trailer drums to AL-KO drums the magnet was using all the bearing surface except for 2mm out of 22mm available. Looks like your magnet should almost be fully mount the full length of square support shaft and is always running on the drum surface. Full use of magnet bearingAlmost full use of magnet bearing surface using 20mm of 22mm availableSpecial spacerMy drawing of magnet to drum distance
My magnet is running 57.5mm from brake backing plate using a 6mm spacer and without the spacer the magnet would only run on 14mm of 22mm available so yes I need the spacer. JR
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Post by nsgnomad on Dec 3, 2023 22:51:31 GMT 10
Quite a process to work it out JR, but at least you got your answer. I never thought about how close the magnets would be with my new backing plates. Haven't had a chance to test them out yet.
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Post by Old Techo on Dec 5, 2023 16:38:38 GMT 10
JR,
That's a nice drawing you knocked up on the back of your hand
When I got my new cheapies I did some measurements too.
I inspected the shoe wear area on my drums to confirm the genuine original drum/shoe relative positioning.
Next I measured the distance from the front edge of the shoe to the backing plate and compared that with the new assembly. They were virtually the same.
I can't remember if I did any magnet arm actual measurements but I did place a rule straddling both shoe edges and looked at the clearance to the tip of the magnet arm.
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Post by jr on Dec 6, 2023 15:53:04 GMT 10
When I originally purchased my Sugar Glider suspension I requested off road magnets which required AL-KO brake shoes and backing plate. I wonder if the location of my axle brake mounting plate is located in the wrong position as over the years I have had uneven wear on the magnets which could be due to the magnet not having enough support on the magnet support arm. Looks like the magnet bearing surface was only about 60% of the available surface. I have found that the AL-KO drums have almost the same position for the magnet running surface as the Melbourne Trailer drum but using the spacer the magnets are now better supported on the magnet support arm so hope my magnet wear will be more even. The supplier of the AL-KO drums said I would need the spacer as the Melbourne Trailer drum runs in a different position but I have found AL-KO and Melbourne Trailer drums have the same running position within 1mm of each other. JR
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Post by Old Techo on Feb 11, 2024 16:17:35 GMT 10
A couple of posts ago I said I would pull off all of the drums.
I did that today to do bearing servicing. It is 2 years and 13,000km since last time.
All work was pretty straightforward but I paid close attention to the newish Trojan brakes.
I checked the magnet wear via the depth of the wear indicators and they were about 3mm deep.
Here is what one assembly looked like...
A closer look at the magnet...
And the only remaining job is to whack a bit of weld on this bolt...
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Post by jr on Feb 11, 2024 18:05:19 GMT 10
OT, I assume the weld is to stop the bolt from rotating. I would weld a small bit of metal next to the bolt head against against say two flats. I carry a 100mm angle grinder to cut the weld to remove the bolt and I don’t even have leaf springs but after the first time helping a frend remove that weld with chisel and hacksaw I am ready the next time. We were out near Cameron Corner in the dirt trying to remove a broken spring not much fun.
JR
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Post by Old Techo on Feb 11, 2024 18:27:50 GMT 10
Correct JR
I tack-weld all of them. If the bolt rotates it cuts into the metal and elongates the hole.
There was someone on the old forum that I think sold small metal plates with a hex hole to match the bolt head. Said plate was to be welded on.
I have replaced my worn bolts a couple of times and the head hex size has varied.
In my pic that bolt head has been butchered by my angle grinder when I've had to remove a weld. I've carried an angle grinder and 2400 watt invertor ever since I bought the caravan new, 20 years ago. Never needed to use it on the road but sometimes off mains-power.
I remember your quite informative post about the Cameron Corner issue.
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Post by bazza44 on Feb 12, 2024 7:04:17 GMT 10
Looking at the photo's OT there appears to be only a vertical hole for the split pin, have you ever thought of drilling a horizontal hole to make adjustment of bearing play easier by using either hole for the split pin through the castellated nut.
Barry
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Post by Old Techo on Feb 12, 2024 7:34:38 GMT 10
Very observant Baz
JR and I have had disagreements about how to set the bearing adjustment.
JR likes to have some preload i.e. tighten the nut a bit passed zero lash. I always did that on my cars but they called for X amount of preload using a torque wrench. For caravan bearings there is strong advice to tighten only with fingers and not a spanner. I'm not entirely happy with no preload but not wanting a bearing failure in the middle of nowhere I follow that finger-tight rule.
The strict rule is tighten with fingers then back-off to the next castellation. I can't live with that much slack
I bought about 6 extra nuts and I swap them until I get finger-tight and exactly lined up with the castellation slot. If none of my spare nuts produce that exact fit then I put one in my lathe to take off a few thou. I think it is 11 thou per castellation slot so easy to calculate how much needs to be removed in the lathe.
Having a second drilled hole in the stub axle would help but it could still be out by more than I want.
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Post by jr on Feb 12, 2024 9:55:38 GMT 10
You have a good memory OT, I had forgot I had posted about the broken springs I did remember the second hole for setting the bearings.
JR
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