Tapping into the air system for toad braking

Topic: Tapping into the air system for toad braking (Read 1975 times) previous topic - next topic

Tapping into the air system for toad braking

August 30, 2021, 02:10:56 pm

I bought a Roadmaster Brakemaster 9160. The car install is done, now I am working on the coach side. Looking at page 10, Step 3 of the directions, https://www.roadmasterinc.com/pdf/85-1809.pdf it says find the air brake relay valve and either use an unused port or tap into an existing with a Tee.

Question
1- Where is the air brake relay valve? On the diagram, is that the Spring Brake Relay Valve?
2- From the right side rear wheel, I took 2 photos, the first is rear, just in front of the axle. You can see the driveshaft in the photo. The second is about 3-4 feet forward. What are these two? If I had to guess, the rear one is the Spring Brake Relay Valve and the front one is one of the SPS valves (what does SPS stand for?)
3- Which should be tapped into and is there a free port or do I have to use a Tee.

TIA, almost there!!

Re: Tapping into the air system for toad braking

Reply #1 – August 30, 2021, 02:39:43 pm

The main thing to note is NOT to Tee into your spring brake air supply. That is unless it is somehow configured exactly opposite to the Airforce One aux braking system. When you release the parking brake, full air is delivered to the spring brake port to keep it released. I would think that your supplemental braking system of whatever brand should use the service brake supply to apply proportionate barking force in the towed vehicle. I had an install that was done improperly by an authorized installer at the "Q". Flatspotted four new tires on the towed. The canisters are stamped as to function (service, spring), but you have to clean the area and get up close and personal to read it.

Note: The picture with the brass TEEW is improperly installed. I took this picture after cleaning the area and sent it to the AF1 head honcho to get him to make the installer reimburse me for four new tires. Small satisfaction for all the time wasted and aggravation felt because of this installer's incompetence.
Don

Quote from: Jason – August 30, 2021, 02:10:56 pm

I bought a Roadmaster Brakemaster 9160. The car install is done, now I am working on the coach side. Looking at page 10, Step 3 of the directions, https://www.roadmasterinc.com/pdf/85-1809.pdf it says find the air brake relay valve and either use an unused port or tap into an existing with a Tee.

Question
1- Where is the air brake relay valve? On the diagram, is that the Spring Brake Relay Valve?
2- From the right side rear wheel, I took 2 photos, the first is rear, just in front of the axle. You can see the driveshaft in the photo. The second is about 3-4 feet forward. What are these two? If I had to guess, the rear one is the Spring Brake Relay Valve and the front one is one of the SPS valves (what does SPS stand for?)
3- Which should be tapped into and is there a free port or do I have to use a Tee.

TIA, almost there!!

Re: Tapping into the air system for toad braking

Reply #2 – August 30, 2021, 03:52:13 pm

I am always leery about making a toad air brake connection.

What do we think happens to our coach braking capability when the air line between motorhome & toad, breaks allowing braking air flow to the atmosphere? Seems like it would be an air leak on a critical hose we would not want.

With so many toad braking systems that do not need us to tap a motorhome brake air lines why not choose them. Air Force taps into an air line, but does not send braking air pressure out to toad, but I prefer simpler systems like iBrake. Understand that some inertia systems will activate with retarder.

Re: Tapping into the air system for toad braking

Reply #3 – August 30, 2021, 04:19:23 pm

Quote

Air Force taps into an air line, but does not send braking air pressure out to toad...

Barry , I believe the above statement is incorrect. While the AF1 uses a small air cylinder actuator to mechanically apply the braking force via the towed's brake pedal, the force is modulated via the metered air from the service brake to give fully proportional braking to the towed. When the AF1 control input is incorrectly Tee'd into the spring brake supply and the parking brake is released, full wet tank pressure is applied to the AF1 control module resulting in completely locked towed brake. IIRC, the AF1 also Tee's into the wet tank for system air pressure and there is a module mounted on the coach side which uses both the service brake metered air and the wet tank but is purely mechanical in nature. From this module which is a sort of regulator and a small reservoir (buffer), a single air line runs to the towed connection.

Re: Tapping into the air system for toad braking

Reply #4 – August 30, 2021, 10:05:13 pm

Don, I have not installed AF1 and also do not prefer them, but I thought one of the advantages ( & additional complexity) of AF1 is it installs with a relay/safety type of device that as you said, gets air from wet tank that flows out to toad under control of the modulated air brake pressure.

Air brake line being only used to open the 'relay's' air line from wet tank. So if when there is a leak from the air line to toad, the source of the air is just the wet tank, which of course will reduce system air pressure, but will not dilute the air going to the coach brakes.

Or are we both saying the same thing.

BTW, with coach/vehicle weight difference being so great, I think modulated toad braking is over marketed.

With a toad air pressure regular set optimally, the toad will never lock up. Toad air cylinder can do a good job by flowing constant coach air whenever coach air brakes are applied. And with portable toad braking systems with integrated air pump, that air pressure can be used in place of coach air.

Re: Tapping into the air system for toad braking

Reply #5 – August 31, 2021, 06:14:35 pm

Quote from: Don & Tys – August 30, 2021, 02:39:43 pm

The main thing to note is NOT to Tee into your spring brake air supply. That is unless it is somehow configured exactly opposite to the Airforce One aux braking system. When you release the parking brake, full air is delivered to the spring brake port to keep it released. I would think that your supplemental braking system of whatever brand should use the service brake supply to apply proportionate barking force in the towed vehicle. I had an install that was done improperly by an authorized installer at the "Q". Flatspotted four new tires on the towed. The canisters are stamped as to function (service, spring), but you have to clean the area and get up close and personal to read it.

Note: The picture with the brass TEEW is improperly installed. I took this picture after cleaning the area and sent it to the AF1 head honcho to get him to make the installer reimburse me for four new tires. Small satisfaction for all the time wasted and aggravation felt because of this installer's incompetence.
Don

Thanks Don, pictures are worth a 1000 words. I was able to see the two on the brake chamber. From the left rear, the one pointing to the center is the Spring (Type 30 port), the one on top is Service (Type 24 port). I'll Tee into the Service.

Re: Tapping into the air system for toad braking

Reply #6 – September 01, 2021, 09:57:36 am

Barry & Cindy wrote "What do we think happens to our coach braking capability when the air line between motorhome & toad, breaks allowing braking air flow to the atmosphere? Seems like it would be an air leak on a critical hose we would not want."

The same thing that happens when an air line, quick exhaust valve or air motor/canister fails: The braking system splits into two and the remaining braking system provides stopping power.

Re: Tapping into the air system for toad braking

Reply #7 – September 01, 2021, 12:02:57 pm

Houston, we have a problem!

I was putting the adapter on and it needed about 2 mils more, it was hitting the 2 piece C clamp around the brake. I started loosening them to see if I could push it over a hair. Well, I ended up loosening too much and the spring popped apart! I have the diaphragm. It looks like if I can get the rearmost piece(piston?) that pushes the front side I can reassemble, but how do you get that piece to retract? What doe the Press Here on the back side of the housing do where the rubber cover is?

If someone has experience with this and can talk, DM me your phone # or vice versa. Thanks in advance.

Re: Tapping into the air system for toad braking

Reply #8 – September 01, 2021, 12:08:38 pm

Quote from: Jason – September 01, 2021, 12:02:57 pm

Houston, we have a problem!

I was putting the adapter on and it needed about 2 mils more, it was hitting the 2 piece C clamp around the brake. I started loosening them to see if I could push it over a hair. Well, I ended up loosening too much and the spring popped apart! I have the diaphragm. It looks like if I can get the rearmost piece(piston?) that pushes the front side I can reassemble, but how do you get that piece to retract? What doe the Press Here on the back side of the housing do where the rubber cover is?

If someone has experience with this and can talk, DM me your phone # or vice versa. Thanks in advance.

People have been killed doing what you did. When in doubt: Don't. Stop and ask questions first. (PM me)

Re: Tapping into the air system for toad braking

Reply #9 – September 01, 2021, 12:13:13 pm

Quote from: Jason – September 01, 2021, 12:02:57 pm

Houston, we have a problem!

I was putting the adapter on and it needed about 2 mils more, it was hitting the 2 piece C clamp around the brake. I started loosening them to see if I could push it over a hair. Well, I ended up loosening too much and the spring popped apart! I have the diaphragm. It looks like if I can get the rearmost piece(piston?) that pushes the front side I can reassemble, but how do you get that piece to retract? What doe the Press Here on the back side of the housing do where the rubber cover is?

If someone has experience with this and can talk, DM me your phone # or vice versa. Thanks in advance.

You need to take the can off, then "key" the spring brake to get it back together. Use google or Youtube to see how this is done.

Re: Tapping into the air system for toad braking

Reply #10 – September 01, 2021, 01:16:19 pm

Congratulations on not getting hurt.

I really don't like dealing with springs. I spent a lot of time designing around the need for springs.

Here's a YouTube video with dirt and stuff on how to cage a spring brake:

https://youtu.be/dwmt3zuRoYA

Re: Tapping into the air system for toad braking

Reply #11 – September 01, 2021, 01:28:36 pm

Here is where I am. Good news is I undid the forward clamp and not the spring brake part it seems, which I now know can be dangerous.

Re: Tapping into the air system for toad braking

Reply #12 – September 01, 2021, 02:09:46 pm

You must block the coach and cage the spring brake to pull the flange back so you can install the other half of the can.

Re: Tapping into the air system for toad braking

Reply #13 – September 01, 2021, 03:41:40 pm

When caging, how far back does the piece need to be pulled back? And then on the front/left side, how do you bring the spring back so it stays?

I have looked at new ones, but my concern is that I will still be in the same situation with the adapter that will not clear the nut.

Re: Tapping into the air system for toad braking

Reply #14 – September 01, 2021, 03:56:04 pm

Cage it and tighten until the nut stops, then you can put the can together, the light spring compresses easy.

Re: Tapping into the air system for toad braking

Reply #15 – September 01, 2021, 05:02:58 pm

Called around, people tend to want to replace this instead of fixing, since they are not too pricey. The pancake is cracked so I am considering getting new ones and letting a mobile mechanic do this. If it is like this on one, the other is probably the same, so may as well do them both.

The mechanic said to upgrade to 3030 over a 2430. Any input on that? Will putting on larger rears impact the fronts? I know they should be done in pairs. Before I have them come out , I'd like to figure this out so I don't have to pay for it twice.

Also, regarding brand, I have MGMs but does it matter what brand? I can get these tomorrow if going with a 2430 https://www.napaonline.com/en/p/TWDHD2430C

Re: Tapping into the air system for toad braking

Reply #16 – September 01, 2021, 05:15:54 pm

Has anyone experienced a brake can failure?
These cans are not difficult to work on. Ive read that people have gone to larger cans but I personally don't see a need currently for me. With the spring brake pressurized to about 60 psi locking is effortless. If you manually retract the spring brake spring with the caging tool on the side of the can make sure you lube the treads to prevent damaging them. Interesting once spring brake is caged it only takes minimal psi to start moving the primary diaphragm setting the brakes. Please post a picture of your damaged cracked part.
Scott

Re: Tapping into the air system for toad braking

Reply #17 – September 01, 2021, 05:24:23 pm

Quote from: Jason – September 01, 2021, 05:02:58 pm

Called around, people tend to want to replace this instead of fixing, since they are not too pricey. The pancake is cracked so I am considering getting new ones and letting a mobile mechanic do this. If it is like this on one, the other is probably the same, so may as well do them both.

The mechanic said to upgrade to 3030 over a 2430. Any input on that? Will putting on larger rears impact the fronts? I know they should be done in pairs. Before I have them come out , I'd like to figure this out so I don't have to pay for it twice.

Also, regarding brand, I have MGMs but does it matter what brand? I can get these tomorrow if going with a 2430 https://www.napaonline.com/en/p/TWDHD2430C

Stick with the 24/30 Your system is set up for it. Changing to the larger 30/30 might cause the rears to lock up.

Re: Tapping into the air system for toad braking

Reply #18 – September 01, 2021, 05:39:11 pm

Pics attached. Oddly, the pancake says long stroke, but I thought they were regular?

I have tightened the cage nut, it's pretty darn tight and I don't want to overtighten it. You can see where the bolt is on the back side as well as the rod on the inside which is about even with the edge of the can. But there is no way I can push the can on the spring on the front and tighten the clamps, I don't have that many hands not to mention the effort is high (I am not a small or older guy!)

Re: Tapping into the air system for toad braking

Reply #19 – September 01, 2021, 05:49:39 pm

look at reply # 16 and you will see how far back the shaft should go into the can. Have you hit the shaft to see if it is stuck. If it bounces the spring isn't caged enough.

Re: Tapping into the air system for toad braking

Reply #20 – September 01, 2021, 06:55:15 pm

Quote from: craneman – September 01, 2021, 05:49:39 pm

look at reply # 16 and you will see how far back the shaft should go into the can. Have you hit the shaft to see if it is stuck. If it bounces the spring isn't caged enough.

I cannot clock it back that far, the tension/torque to do it is very high and I don't want to break something. I tapped on the shaft, no play, it's very tight.

Re: Tapping into the air system for toad braking

Reply #21 – September 01, 2021, 06:59:34 pm

Buy a couple of new cans if the shaft is frozen, they won't let you kill yourself. They sealed the band on the spring brake side of the chamber.

Re: Tapping into the air system for toad braking

Reply #22 – September 01, 2021, 07:53:44 pm

Quote from: craneman – September 01, 2021, 06:59:34 pm

Buy a couple of new cans if the shaft is frozen, they won't let you kill yourself. They sealed the band on the spring brake side of the chamber.

Yep. X2 If in doubt toss it out.
Scott

Re: Tapping into the air system for toad braking

Reply #23 – September 01, 2021, 10:01:33 pm

Quote from: Jason – September 01, 2021, 05:02:58 pm

Called around, people tend to want to replace this instead of fixing, since they are not too pricey. The pancake is cracked . . .

That's because this is a life safety part. Remember that you're driving a 30,000 pound truck. Stopping is important.

Re: Tapping into the air system for toad braking

Reply #24 – September 01, 2021, 10:14:14 pm

Appreciate the helpful replies today @craneman and @dsd. I was trying to get away this weekend but that doesn't look like it's happening now. I am going to get new rears, may get them by Friday otherwise next week. I do not feel comfortable at all cranking it any tighter as I mentioned.

I will look for a write up/vid on installing new cans and adjusting and decide if I want to tackle it or call it in.

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