| Author |
Message |
Michael Jass (Michael) (205.210.232.66)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, April 26, 2001 - 5:12 pm: | |
I was getting my bus ready for a spring runout. When I pressed the brakes and released, they did not return by their own spring pressure, so I removed the wheels to inspect the brakes, the S-cams and rollers were all rusty. They were begging to be disassembled cleaned and greased, to do this I must pull the drums. Holding the drum onto the wheel hub are 5 slot type screws with tapered heads, the heads are about 1/2". These screws are quite rusty, they look rust welded to the drums, and the slots look more like valleys! In a feeble attempt (just to humour myself) I took a large screw-driver to them, nothing but flakes, not surprised. So the question to the "been-there done-that" crowd is... Should I just center punch and drill out these screws, and if so how big are the actual screws? Or is there some black magic available to us bus converters that will allow us to remove rusted screws and bend spoons with out minds?
Michael
1982 Prevost Champion
michael.jass-at-cognos.com |
Jim Ashworth (Jimnh) (172.149.90.227)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, April 26, 2001 - 8:17 pm: | |
Instead of removing the drum, which can result in mis-alignment when reassembling, pull the hub/drum together. 6 screws on the hub cap and one (or two) huge nut(s) inside. When reassembling, tighten the nut tight and spin the wheel to seat the bearings, then back off for running clearance. The hub/drum combination is heavy, especially on the drives, so use a floor jack to support it and roll it in place.
Jim |
Clarke Echols (216.17.134.112)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, April 26, 2001 - 9:58 pm: | |
When pulling the hub by removing the bearing nuts, when you reinstall, tighten the nut to 100 ft-lbs of torque then back off 1/6 turn (as I recall -- check with an authorized Rockwell axle rebuilder. Learned that years ago at Drive Train Industries in Denver. Then install the lock plate and jam nut over the first nut.
Also, NEVER NEVER NEVER EVER grease the S-cam rollers and the S-cam where it contacts the rollers. Only grease the bronze bushings that hold the S-cam shaft in place. Grease on rollers attracts dirt which leads to all kinds of bad problems. |
madbrit (216.67.204.234)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, April 26, 2001 - 10:41 pm: | |
According to the MCI manual, to adjust the rear wheel bearings, is basically as follows:
Whilst rotating the wheel (doesn't say which direction) you tighten the bearing until the wheel binds. Then slacken off the adjusting nut about 1/8th of a turn to make sure the wheel turns freely. Then reassemble the lock rings, nuts, etc.
My suggestion to you is to get the manual particular to your vehicle and do what it says. |
Steve Fessenden (63.27.88.15)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, April 26, 2001 - 11:35 pm: | |
The way I saw the screws removed was to place a punch on one side of the groove in the slotted screw and tap solidly with a heavy hammer in the direction you want the scew to turn. They loosened right up. What I saw, watching a mechanic.
Steve Fessenden |
jmaxwell (66.42.92.111)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, April 27, 2001 - 1:32 am: | |
The center punch on the side method works good, better after a good dose of penetrating oil. Also, you could try a hand held impact driver with a heavy hammer and a firm grip. Mine is capable of 1000# torque, but it hurts like hell if you miss the driver. |
jose (192.55.114.156)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, April 27, 2001 - 5:44 pm: | |
The best method is to use a torch to heat the heads red hot then wait till they cool completely,
You may have to do this twice. Be careful useing force as it is common to have one side of the screw head break off,the head is not very thick. It is also common to see that all these screws were not replaced, useing the lug bolts, and wheels to hold the drum in place.
Jose |
Jim Ashworth (Jimnh) (172.148.51.6)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, April 27, 2001 - 7:17 pm: | |
OK, Here it is from Rockwell. Torque to 100 lbs and spin the wheel in both directions. Back off and re-torque to 20 lbs. For single nut with cotter pin, back off from this 20 lb. torque 1/8 turn, for double nuts back off 1/3 turn. End play in either case should be .001" to .005". It is proper to grease the shaft of the rollers that contact the brake shoes but not the roller surface that contacts the S-cam. This allows the roller to turn on the S-cam and not cause flat spots on the roller. When you do replace the drum, be sure to use phillips head brass screws. They drill out easily with a tap drill sized drill since the drill will self-center. Removing the remaining thread portion is a snap with something as simple as a pocket knife!
Jim |
Michael Kennedy (63.24.128.40)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, April 27, 2001 - 9:19 pm: | |
I have a question for you Michael. Did you happen to pull the brake pedal up by hand and see if this releases the brakes? A spot of rust ect. can and will not allow the brake pedal air control to fully release. |
Claimjumper (216.190.28.34)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, April 28, 2001 - 7:59 pm: | |
An excellent method for removal of screws is to use a left wound drill bit, in most cases it will remove the stub while drilling.>>>Dan |
Tony Wahl (64.12.101.167)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, April 28, 2001 - 10:30 pm: | |
Hi Michael,
I spent 6 hrs w/ a punch and a 4lb hammer to get loose of just one drum (5 half inch machine screws).Then my neighbor,who is a mobile truck tire repair guy, took pity on me (or maybe he did the math and couldn't take 18 more hours of me banging away w/ that hammer) and rolled his tig welder over and he tac-welded 1/2 inch hex nuts onto the screws and they came right out w/ a socket and breaker bar. We had all the drums off in about an hour.
Good luck,
TonyW |
Mark Domeck (Prevost3406b) (152.163.205.78)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, April 29, 2001 - 3:08 pm: | |
I usually take a torch and heat the drum screw to break the rust free and if it doesnt break free, carefully blow the screw out w/o hitting the drum or hub. When you heat the drum screw, let it get red hot and then cool down, then try to remove it. You need to replace the oil seal. As far as tightening, I always torque the wheel down to 50 ft. lbs. while rotating the wheel the same rotation as the nut, back off and finger tight, then impact the jam nut down. As a truck/ bus mechanic, that is the way we do it. |
Michael Jass (Michael) (205.210.232.66)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, May 01, 2001 - 4:22 pm: | |
Thanks for all the great responses, I haven't had a chance to get back to it yet, maybe this weekend. I'll try the center punch with heat first and see what that gets me. I like the Idea about the brass screws, but are there any shear forces on these screws during braking? Ya I know if the wheels are torqued properly there should be no forces on these screws...
If I can't get the screws out I'll undo the bearing, like I do to remove the front drums from my old Cadillac, the torque specs are in the Prevost service manual are just like Jim reads it from the Rockwell manual.
Yes I did try to pull the brake pedal back, I discovered that trick when I thought my parking brakes wouldn't release. A buffing wheel, rust inhibitive paint and some grease solved that one. (the rusty pedal was a result of a water trickling in from the front cap.) |
Frank Walka (Ivirfrank) (64.12.101.153)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, May 05, 2001 - 1:10 pm: | |
I belive the drum screws are just there for assembly purposes. The hub flange locates the drum and the clamping of the wheel studs and nuts holds it tight. Where I worked, we removed those screws the first time and never put them back. Never had any problems, and we still had to beat the drums with a sledge hammer to get them off the hubs. |