| Author | Message | ||
| Larry & Lynne Dixon (Larry_d)
Registered Member Username: Larry_d Post Number: 206 Registered: 7-2005 Posted From: 71.111.182.79  Rating: N/A |
I have an air switch under dash to drivers rite, says dry road and slick road. Switch looks the same as used for rearend lock up on the old log trucks. Thanks all 4905 Larry | ||
| Clint Hunter (Truthhunter)
Registered Member Username: Truthhunter Post Number: 174 Registered: 1-2009 Posted From: 24.129.232.82  Rating: N/A |
Usually switches marked like that limit pressure to the front axle brakes on wet, slippery roads to reduce brake lock up skidding. No first hand knowledge on 4905. | ||
| Bill Gerrie (Bill_gerrie)
Registered Member Username: Bill_gerrie Post Number: 261 Registered: 3-2006 Posted From: 216.198.139.38 Rating: N/A |
Larry It is a front brake limiter for slippery conditions. I think they are illegal now. Maybe BW will chime in here. He is up to date on this stuff. Bill | ||
| David Guglielmetti (Daveg)
Registered Member Username: Daveg Post Number: 36 Registered: 2-2009 Posted From: 64.163.110.102  Rating: N/A |
With regards to "illegal", I would think that if the vehicle came with it that it would be legal. There has been no "retroactive" type stuff other than the reflective tape on big trailers. | ||
| Buswarrior (Buswarrior)
Registered Member Username: Buswarrior Post Number: 1578 Registered: 12-2000 Posted From: 76.71.102.171  Rating: N/A |
Back in the day... It appears that you have a manually controlled front wheel limiting valve installed in your coach. First, it is EXTREMELY rare to find one of these on a coach, this was, however, a popular option for highway tractors. Installing one on a two axle vehicle is not well regarded from the vantage point of 2009. Here's the flawed theory: It was feared in a belt and suspenders and personal experience kind of way that under heavy braking in the wet that the front wheels would lock up and the driver lose control. Also, axle laws were not what they are now, some wild and wonderful things could be done with a highway tractor and the positioning of the load on the trailer to induce front wheel skidding that simply is not allowed today. In an attempt to prevent this, the front wheel limiting valve was invented, the one controlled by your "Wet/Slippery" valve. This valve will manually cut the applied pressure to the front wheels in half when put in the "Wet" position. (if it is installed correctly and is actually present, you need to trace some plumbing!!) And then there was no wheel lock on the steers. Trouble is... what happens to the stopping distance if you reduce the squeeze on the front brakes? Lengthens by a lot. Some may recall the good old days with no brakes at all on the steer axle of highway tractors.... Again, stopping distance given away and nothing in return. Modern testing suggests that if conditions are sufficient to lock the fronts, the rears are going to lock too, so you are giving up stopping distance and not getting anything in return. In slippery conditions, you want anything and everything with some traction doing some slowing down for you. Another trouble...Drivers would forget to put them back to dry road/full pressure, other vehicles were rear ended.... In the middle times, they developed automatic front wheel limiting valves for these purposes. No driver involvement, just step on the brakes. Partial brake application was reduced pressure, a heavy application allowed full pressure. These led to greater wear/load being placed on the rest of the brakes that were doing proportionally more work. Really tricky during light downhill braking, as some of the relay valves weren't cracking open, the fronts were auto limited, only an axle or two might be rubbing...smoke and stink, etc.... In modern times, the ABS equipment takes care of these matters, if slippery roads and braking are to cause any grief. If the coach were mine, I'd trace out the lines, remove the limiting valve from down below, and leave the dash control as a trophy piece. I don't think you will find a brake systems engineer supportive of its continued existence in your coach. happy coaching! buswarrior | ||
| Buswarrior (Buswarrior)
Registered Member Username: Buswarrior Post Number: 1579 Registered: 12-2000 Posted From: 76.71.102.171 Rating: N/A |
Oh, and in the meantime, just leave it in the dry road position. If you like, go do a little brake testing. See what difference there might be between the two settings during a panic stop. Some semblance of scientific method should be used, if the seat of your pants indicates little difference. happy coaching! buswarrior | ||
| David Guglielmetti (Daveg)
Registered Member Username: Daveg Post Number: 38 Registered: 2-2009 Posted From: 64.163.110.102 Rating: N/A |
Good idea BW. The testing that is. | ||
| Douglas Wotring (Tekebird)
Registered Member Username: Tekebird Post Number: 395 Registered: 10-2004 Posted From: 71.59.75.212 Rating: N/A |
not that uncommon in that era Coach | ||
| Bruce Henderson (Oonrahnjay)
Registered Member Username: Oonrahnjay Post Number: 406 Registered: 8-2004 Posted From: 76.21.223.150  Rating: N/A |
Larry, when was your coach built? | ||
| Larry & Lynne Dixon (Larry_d)
Registered Member Username: Larry_d Post Number: 207 Registered: 7-2005 Posted From: 71.111.182.79 Rating: N/A |
Bruce The number is 831, registration says it is 1975, but I really think it is a 1974 due to serial #. I have no other idea except maybe it was rite at the end and start of years. Regards the switch, For some reason I thot it may have had something to do with the tag. I had idea from build sheet that it had a tag when it was new. When I got the coach two outside metal wheel well trim came with it. Also know where it was delivered, thanks to help from this board of very nice people..Larry | ||
| Jack Hart (Jackhartjr)
Registered Member Username: Jackhartjr Post Number: 50 Registered: 8-2007 Posted From: 64.12.116.203 Rating: N/A |
I wonder if it was indeed for a tag axle too. The Scenicruisers have a dump switch for the tags that let the driver dump the tag air in order to put more weight on the drive in snow and ice. Without checking the regs, I think the front brake 'kill' switches went out in the early 70's. Not sure though. Jack | ||
| marvin pack (Gomer)
Registered Member Username: Gomer Post Number: 459 Registered: 3-2007 Posted From: 71.55.197.237  Rating: N/A |
Larry; if your coach came with a tag axle it was one that would partially take up the back bay. If you have a manuel it will show all that in da book. I think that yours may have had one and the switch was to let the tag axle retract in the bay and let the drive axle have the weight to control the road conditions. I think that is right but I have only been mistaken once and I was wrong then. LOL Gomer | ||
| Larry & Lynne Dixon (Larry_d)
Registered Member Username: Larry_d Post Number: 208 Registered: 7-2005 Posted From: 71.111.182.79 Rating: N/A |
Gomer and Jack The rear bay on the passenger side hold the propane and is covered can't see any of the bay, the driver side has all of the tanks. I just put the books away in a hard spot to get out, I will pull all of them out and check what the coach had on delivery and look for the switch use this weekend. Should have done it first, boy am I lazy. I will let you know what I find. I'm still waiting for the genset to get fixed, as it sounds like the better half has some dog shows in two or three weeks. If so slidout will have to wait............oh well. Thanks much for the come back and info 4905 Larry | ||
| Larry & Lynne Dixon (Larry_d)
Registered Member Username: Larry_d Post Number: 209 Registered: 7-2005 Posted From: 71.111.182.79 Rating: N/A |
More info, The coach was delivered with a tag axle, it was taken off at conversion time. I have checke Da Book didn't find the switch in it. I will send Luke an email I'll bet he can for sure tell what it is. Also I found the horn button on the floor it was kind of hidden under carpet. I replaced the rubbers in the hinge of the genny door went very well with dish soap. Works find now, thanks for the info on this board. What would I do without all of your help. I have had amp and a half float chargers on start batteries and genny battery since a year ago and no more dead batteries. The start batteries are 8D. Thanks everyone and esp. Ian. 4905 Larry | ||
| Don Evans (Doninwa)
Registered Member Username: Doninwa Post Number: 202 Registered: 1-2007 Posted From: 208.81.157.90  Rating: N/A |
May be pure rumor and I don't remember when or where I heard it but was told that some bus companies had 4905s set up to retract the tags when going though toll booths to avoid the extra axle toll. True, false, have no idea. Don 4107 | ||
| marvin pack (Gomer)
Registered Member Username: Gomer Post Number: 468 Registered: 3-2007 Posted From: 71.55.197.237 Rating: N/A |
TRUE TO THE BONE DON, Also when they didn't have passengers it would use less fuel[believe that] Anyway?? gomer |