| Author |
Message |
Rick 74 MC-8
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, February 24, 2005 - 5:50 pm: | |
Could someone tell me what the applied air psi (Close range ) is during a normal stop I want to put an air cylinder in the toad. applied psi will help with diameter and location on the petal asem
Thanks Rick 74 MC-8 |
gusc
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, February 24, 2005 - 6:14 pm: | |
Applied brake pressure varies with how hard you push the pedal, it is not a constant. |
Bill Glenn
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, February 24, 2005 - 7:00 pm: | |
wELL Rick;
Needless to say, o psi @ o petal pressure, I would say at morderate 1/3 brake actuaction, pressure would be 45#,90# is probably hard (normal) stop(what the he!! is normal).
My pressure tops out @ about 130 #, so I guess that would be 100%,,,,wOAAAAA, SOME A$$ H*!$ STOPPED IN FRONT OF ME.
What is asem? bly?
If you develop a good toad break system based upon this explanation, cut me in.
Close as I can magin.
Bill Glenn 73 Eagle |
Rick 74 MC-8
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, February 24, 2005 - 7:52 pm: | |
I plan on teeing into the tag brake and running that to an air cylinder pushing on the brake pedal. Applied air psi will determine what diameter air cylinder I use. As far as safety if I put a small orifice inline so even if the line brakes I will still have brakes. Breakaway will be an air tank with a 3 way solenoid I will test the system with the air tank at different pressures. I don’t want to smoke the brakes or tires on the toad!! I guess I’ll just start at 100 psi and work down from there
Rick 74 MC-8 |
CoryDaneRTS
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, February 24, 2005 - 8:04 pm: | |
Are you talking about Power Brakes???
If so, don't you have to maintain a vacuum for the power assist??
How will you maintain the vacuum for the power assist?
There are some kits out there that includ a vacuum pump but use an electric actuator for the brake pedal.
This is a site of a GMC MH owner who installed a system on his toad...
http://www.gmcmhphotos.com/gallery/showalbum.php?aid=19&uuid=arch
Perhaps this may be helpful
cd |
Rick 74 MC-8
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, February 24, 2005 - 8:38 pm: | |
Power breaks work without vacuum
Rick 74 MC-8 |
Craig Craddock (Gs4)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, February 24, 2005 - 8:40 pm: | |
Toward the bottom of page 3 of this site. How to build a -----. I believe will answer your question.
http://users.cwnet.com/~thall/fredhobe3.htm |
t gojenola
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, February 24, 2005 - 8:43 pm: | |
I would use a cylinder that delivers a pressure equal to or slightly over the maximum air pressure that could be delivered. Say one with a 1" bore. But I would feed the air through an adjustable regulator rather than an orifice. Then I would adjust the regulator to achieve the desired braking action.
Have a look at this site - these guys have done it and sell the product, but the literature practically shows you how to make your own.
for the brake applicator:
http://www.supersteersuperstop.com/ss-fitzall.htm
for the breakaway device:
http://www.supersteersuperstop.com/ss-brakesaway.htm
I think I would improve on the system by adding a means of actuating a monitor in the coach, and a way of actuating the 4-way flashers on the toad in the event of a break-away or malfunction.
tg |
Pete/RTS Daytona (Pete_rtsdaytona)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, February 24, 2005 - 9:19 pm: | |
Here's a very interesting site - GMC Classic Motor Homes - $30 toad brake setup - made from a '80's ford cruise control module and a vacuum pump -
http://www.gmcmhphotos.com/gallery/showpic.php?aid=291&uuid=kenhenders&pid=3065 |
Chuck Newman (Chuck_newman)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, February 24, 2005 - 9:49 pm: | |
Rick,
My M&G cylinder is 4" diameter. It sets between the vacuum booster and hydraulic master cylinder. It does not over stress the brake pedal shaft, particularly with heavy toweds. Check out
http://hotrodparts.com/rv/mg-brakes.htm
"Power breaks work without vacuum". That's true only if the system is air-over-hydraulic. Otherwise the vacuum booster gives you the "power".
Chuck Newman
Oroville, CA |
Brian (Bigbusguy)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, February 25, 2005 - 12:12 am: | |
Some good info , And some realy nice ones.
Im going to use a spring brake and two air lines I will set it up just like a semi trailer with the same valves so after the brake away I will not lose any air on the coach.
Im not to worred about sliding the tires after a brake away Its better to buy some tires then have my towed fly off the hwy.
Brian 4905 Klamath Falls Oregon |
Sean Welsh (Sean)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, February 25, 2005 - 12:44 am: | |
Rick,
I seldom go over 30psi on a "normal" stop. 60psi is pretty much full-emergency.
But I'm concerned by your plan. You can't simply tee the air line and run it to the toad -- if the toad breaks away, you'll lose all your brake pressure (even through a small orifice, as you suggest). That will leave you with either no brakes, or an immediate emergency brake application (depending on the type of brakes on your coach). Either case can be deadly, which is why it is illegal in all 50 states to have this type of trailer brake setup on an air-brake equipped vehicle.
You are required to have what is called a "tractor protection valve" installed in the lead vehicle (your coach), which feeds the air to your trailer brakes. The TPV, which is often integrated with an independent trailer brake application handle (called a "trolley valve" or sometimes a "johnson bar"), closes immediately if it detects a complete loss of pressure on the trailer side, thus "protecting" the tractor (bus) air supply.
-Sean |
Richard Bowyer (Drivingmisslazy)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, February 25, 2005 - 8:25 am: | |
I have the M&G system on my 99 Tahoe. As far as I can determine, it has no breakaway system. It was hooked to the bogie axle brakes I believe, but since I did not install it, I am not sure. I still have the assembly on the Tahoe if someone is interested. Maybe I should have put this in with my request for information for a rental shop BB. LOL
Richard |
Rick 74 mc-8
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, February 25, 2005 - 10:09 am: | |
Thank you Sean
That’s all I asked. Sometimes I hesitate to post. It seems a lot of people just want to criticize your question instead of answering it. I agree constructive cridassiom can be a good thing but I must emphasize constructive.
Thanks Rick 74 MC-8 |
Jim Wilke
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, February 25, 2005 - 10:41 am: | |
I think the bogie/tag axle brakes use less air pressure to prevent them from locking up. Check out the brake system section of your manual before making your choice.
Jim-Bob |
mel 4104
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, February 25, 2005 - 11:32 am: | |
it may depend on how heavy your toad is and the size of the tow vec. how ever with my 4104 pulling a excad mazda pickup i had no trouble stopping both when the ball from the hitch failed as the safty cables were stromg enough to hold vec. together just use 2 cables or chains that have good fastners on each end that have to be undone to disconnect and will not pull apart which will keep them together. also if you are going to use air use a 2 needle air gauge , one will show the air in the main tank the other will show your applied air . oh yes when my tow vec seperated it was on I-5 coming into Weed Cal. which is hilly country. |
Sojourner (Jjimage)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, February 25, 2005 - 3:14 pm: | |
About air pressure for your air-cylinder, it depend the diameter of piston as well leverage point on brake pedal’ arm.
Such as cylinder dia. 1inch @ 100psi equal just over 78 lbs of force.
2 inch cylinder will give you 3.14 times the air psi. (314 lbs of force @ 100psi)
http://www.engineersedge.com/calculators/area_calculator.htm
Location for cylinder point to brake pedal’s arm determine distance between pivot point to foot’s pad. A known driver’s foot pressure in lbs for panic stop.
Formula is driver’s foot force x distance between pedal to master cylinder’s push rod / (divide) by distance between master cylinder’s push rod to arm’s pivot point equal lbs of master cyl. push rod’s force.
Such as 100 lbs pedal pressure, 10 inch, 4 inch equal 250 lbs.
To figure air cyl. to arm point location, 100 pedal with 10 inch leverage for 1 inch point equal 1000 lbs.
Divide inches between cyl. arm to MCPR point into 1000.
Such as cylinder force @ 2 inch above pedal (8 inch to MCPR) equal (1000 / 8) 125 lbs.
So you need whatever air cylinder dia. @ whatever air psi to push 125 psi to meet 250 lbs @ MCPR point.
If motorhome or coach already have air brake, air cylinder to tow’s brake pedal is better alternative over vac or electric.
Caution; I am not responsible for any damage it may occur using the following suggestions. You are at your own risk for any damage it may cause. Do-it-self’er or installers are responsible for your or their actions.
Be sure to have air tank (about 1 cubic) in car for “break-a-way stand-by” using check-valve at inlet of tow’s tank and a relay-emergency-valve (truck & semi-trailer) to apply full regulated air pressure to cylinder.
Setup is similar to semi-truck system.
1) Line one is full air supply pressure from coach to tow’s air tank and to relay’s diaphragm.
2) Line two is brake’s air pressure thru relay valve to cylinder.
3) Can use new or used “glad-hand” for breakaway hose connections.
http://www.sloantrans.com/catalog/2003%20PDF%20Catalog/Gladhands%202003.pdf
They have to be installed so it will turn glad-hand to disconnect when pulled and automatic shut off valve at coach’s ends.
FWIW
Sojourn for Christ, Jerry |
CoryDaneRTS
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, February 25, 2005 - 8:45 pm: | |
Is there a reason you want to reconstruct your brake system for the toad?
I am not criticising, just wondering.
In my above post, the aux toad brake, can panic brake and has break-away capability as well as normal braking operation, all in a simple self contained package.
If I see this right, you are talking about tampering(or re-engineering) with the bus air brake system, adding hose and connections, valves and then you have to construct and test and make work a cylinder, possible regulator, more hose and tie into the toad brake system with yet another system that you have to build, test and make work.
Frankly, I am confused. Of course you may have a very good reason to do this. On my bus, I would be concerned about tampering with the original bus parts/hoses/connectors and then adding additional parts.
What was that saying "if you don't have to mess with it, DON'T!"
Besides that you are looking at having to mess around with additional hoses and valves to connect to the car, versus a plug.
I guess I am not all that mechanical so I would go the electrical method, perhaps you are a machinist and enjoy the adventure of re-engineering the bus brake system.
Being the worry wart that I am, I would worry that I crack something in the rebuild, or if the hose will fail or connectors, oh my.
The item I found also seems to follow the KISS methodology and keeps the bus system on its own operational system.
But, every person must follow their own path.
Hope you did not take offense to my mention of this idea. I just felt it was worth the mention.
cd |
Tim Jones (Torquester)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, February 25, 2005 - 10:14 pm: | |
Rick, I'm not trying to flame you here but what you are trying to do here is not a good thing. If you tee the applied air from your tag to supply your toad, you will be changing the timing of the original braking design of your coach. This could actually increase the stopping distance of your vehicle. Please consider a system which is designed by competent air brake engineers to work in conjunction with a hydraulic system. In my opinion... no toad brakes would be better that what you plan to do.
hth, Tq |
Sojourner (Jjimage)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, February 26, 2005 - 10:15 am: | |
You do whatever it please.
In the 60’s I have work in a large Michigan meat packing plant as semi tractor & trailer & sausage truck mechanic. That before all trailer change to air springs.
About affecting the amount of coach’s air brake line to tow’s cylinder. Amount of air to cylinder is about same as one coach’s brake can. Look at another way, set all coach‘s “slack adjuster” 1/32 inch more travel, you will about the equivalent displacement of tow’s cylinder. That so small to hardy notice.
However the main important is the coach’s outlet near hitch is equip to stop air leak whenever the break-away occur. There valve available that when pull hose from coupling will stop air leak or flow.
Similar to gas station use on pump’s hose.
Or tractor protection valve such as Bendix CP-2 http://www.bendix.com/downloads/service_data_sheet/033651.pdf
All of the parts can be available from truck’s salvage yard. They need cleaning and white lube all moving parts. Use proper replacement “O” rings if needed.
If you want new units or parts, all brand large truck service center will help you fill your needs.
Chapter 7 on truck air brake;
http://www.icbc.com/Licensing/PDFS-CommVeh/MV2677%20ch%2007web.pdf
FWIW
Sojourn for Christ, Jerry
PS if you want to e-mail your concern…remove X’s from address. |
Rick 74 MC-8
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, February 26, 2005 - 1:04 pm: | |
Thanks
I understand how the brake system works and am aware of the safety concerns I Don’t think a typical trailer system would be a good think because the toad braking system would not be sufficient to stop the bus should the toad system fail it might just smoke the brakes on the toad. I will run steel lines (same as the original bus) from the connection tee and put a shutoff valve and a quick coupler at rear of bus with flex line from there. I have built many Race cars from the ground up and do all my own maintenance on the bus. I thank everyone for their concern. I don’t type well so I tend keep things brief in my posts. I guess some people just nervous. I also believe in the kiss method but won’t compromise safety
Rick 74 MC-8 |
Brian (Bigbusguy)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, February 26, 2005 - 1:52 pm: | |
Rick
I would still us a tractor protection valve .
Im sure your bus line would be fine Im doing mine with air for the towed also. Its the lines going to your towed car if one was to brake you would lose your bus air for stoping quickly or 1/2 of it if you have a duel air system .
If you have a trailer air valve you can shut off the air to the towed when the tractor protection valve closes the air off also. Also its req. by law to have one if you use air for you trailer.
Im going to use quick disconnects for shop air hose to make my connectoins at the rear.
Brian 4905 Klamath Falls Oregon |
Buswarrior (Buswarrior)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, March 01, 2005 - 10:42 am: | |
Rick,
I will add my words of caution to those already here.
You shouldn't just carve into an existing brake system with add-ons. My only exception to that rule would be if you have QUALIFIED engineering advice.
Mechanics are not qualified to give this advice. They have not received any training related to the engineering of a brake system. They are taught, maybe, how to diagnose and repair defective parts. This is not a flame, it is the truth. Design and repair are two completely different disciplines.
Backyard common sence does not equip us with qualification.
Those of us without education are fond of being sceptical of those who do. Those of us with education are fond of thinking those who don't..... Well, brakes is an area that attitudes have to be checked at the door.
My only concern is safety, and those who might be reading this and beginning to feel empowered to mess with their brake system.
My questions might be:
Where are you planning to tee into the existing brake system?
How will that connection affect the existing brake timing and brake balance?
How might it effect the strength of the existing brake system on application?
How will you compromise or enhance the safety of the existing design?
What effect will your modification have on regulated tank volumes?
How will the vehicle respond to a failure of your modification?
What would a qualified commercial vehicle enforcement officer think of your modification, should he or she ever happen to look over as they drive past your rig?
What would your insurance company think of your modification?
If you are hell bent to continue, please consider using a relay valve and teeing to the signal line, not a delivery line.
If any of the above makes no sence, then you shouldn't be messing with your brake plumbing....
happy coaching!
buswarrior |
niles steckbauer (Niles500)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, March 01, 2005 - 4:43 pm: | |
BW - hi! - nice to hear from you - you don't post much any more - but when you do - its pure genius - Niles |
Buswarrior (Buswarrior)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, March 02, 2005 - 9:39 am: | |
It's a time thing...
sometimes I got, sometimes I don't got.
Thanks Niles!
happy coaching!
buswarrior |