Brakes Released Meaning
Carol Gudes
All vehicles with air brakes must have a way of stopping if the service brake system fails. Most vehicle manufacturers combine this emergency braking system with a parking-brake system using spring brakes.
Spring brakes use a different type of brake chamber from service brakes. A brake chamber that includes both service brake and spring brake sections is called a spring brake chamber. Spring brake chambers apply the brakes by means of a large coil spring that provides enough force to hold the brakes in the applied position, instead of using air to apply the brakes.
Many vehicles can still be driven even with the spring brakes applied because they do not have the braking power of the full service brake application. Before driving the vehicle, it is important to ensure that the air brake system has enough air pressure (normally 414 kPa (60 psi)) to keep the spring brakes from applying. Due to the way most spring brake chambers are currently constructed, it is very difficult to unintentionally release the spring.
The large coil spring used in the spring brake chamber is compressed under very high tension. Tampering, damage or corrosion can cause the spring to release, resulting in sudden violent motion of parts of the air brake chamber. Since this can be hazardous, never attempt to service or repair any air brake chamber.
Using a "caging bolt" or other mechanism, a technician can manually compress or "cage" the spring in a spring brake chamber. This may be necessary to move a vehicle in an emergency. When a spring brake chamber fails, a technician may use the manual caging method to temporarily disable it. A spring brake chamber that has been disabled by this method looks different and the parking and emergency brake will not apply. Disabled or caged spring brake chambers can be recognized by the protrusion of the caging bolt or other similar mechanism. Drivers encountering a disabled spring brake chamber should have the vehicle inspected and repaired immediately.
A spring brake control valve is normally a push/pull type valve fitted with a yellow, four-sided knob located near the driver (See diagram 4-3). Most spring brake control valves are pushed to supply air and release the spring brakes, then pulled to exhaust air and apply the spring brakes. Some vehicles may have this function reversed, but its functions are normally described on or near the control valve. Some vehicles use a toggle type valve for this purpose. Drivers must be familiar with the type of control valve used in their vehicle.
Some trucks and tractors may also have a separate control called a tractor parking-brake control valve to release the spring brakes on the tractor while keeping the trailer spring brakes applied. This optional control valve normally has a round blue knob.
Spring brake control valves are designed to respond to air brake system pressure dropping below a certain level (normally 414 kPa or 60 psi) by exhausting the remaining air that is holding the spring brakes in the released position. This causes sudden automatic application of the spring brakes and an uncontrolled vehicle stop. The control valve knob will pop out when this occurs.
Many buses and motor coaches are fitted with parking and emergency brakes that do not use a large spring in the brake chamber. This type of chamber is called a DD3 Safety Actuator. Although similar to a spring brake chamber, a DD3 brake chamber has three air line connections instead of two. Internally, these chambers have a mechanical means of locking a brake in the applied position. A control valve similar to the one used in conventional spring brake systems applies the emergency and parking brakes. Releasing the spring brakes requires operating the control valve and then pressing the brake pedal for three to five seconds.
I'm using a TEU-104BK ESC which is set up with brakes. I expected the brakes to bring the car to a stop but they more kinda slow it down a bit, not much use when you're heading for something solid. If I come off the brakes and then hit reverse I can get it to stop (with a skid) but this takes time. I suppose I expected the rear wheels to lock up when brakes are applied but they don't.
For that ESC brakes means a pulse of a given duration to stop the car, the weight of the car and speed determine if it comes to a complete stop or just slows down with the pulse given. If you do use reverse to brake for a longer duration it tends to blow up the reverse transistors and then it's done.
Hi Dave, actually the TEU-104BK is a "two step reverse" type of ESC. The first time the transmitter sends a reverse signal, the ESC acts as brake only, and there is no time limit for how long they can be applied. To get reverse motor operation, the transmitter must go back to neutral and then reverse again without going forward. This is the same as the TEU-101BK (discontinued) and TEU-105BK.
2. The motor. The stock RS-540S does not have a very powerful magnetic field, so when the brakes are applied, the braking torque isn't as pronounced as, say, a 27T Epic/Trinity/Reedy/etc. stock or modified motor with 5.0 wet magnets. If you've ever tried to spin a Mabuchi 540 motor shaft and then a 27T stock motor using your fingers, you'll know what I mean.
In my opinion, switching to a different ESC isn't going to make any difference in braking unless the ESC actually sends reverse current to the motor in some way (which is the only way the brakes can be made more powerful than directly shorting the motor leads which is what maximum brakes is already) and I don't think any ESC does that. The only things that will make a difference is altering driving style, meaning that you need to understand that it takes longer to stop the Sand Scorcher than other lighter chassis vehicles and it must be accounted for, and/or swapping the motor for one with more powerful magnets. But mounting such "open endbell" motors in the SRB chassis is a huge pain and generally not recommended.
Compare the brakes on a TEU-101BK ESC and then on a TEU-104BK ESC. It's like the 50% reverse power of the TEU104 is also only 50% brake power. TEU101 is 100% reverse and does work much better in an SRB, even with the silvercan motor.
Mark, I am glad you posted this. Honestly I had typed in exact same thing into my reply, but then removed it before posting because I didn't know if it was correct or not. I did not know if the brakes on the TEU-104BK were limited to the same "50% of maximum power" like reverse. Since they are separate functionality, and because I thought brakes were an very important feature of any speed control, I figured they would have been 100% as powerful as the original TEU-101BK's brakes. But you've just shot that idea down. It's been so long since I drove a 101 that I couldn't remember braking differences. So that invalidates what I said about a new speed control being any better than Dinsdale_71's TEU-104BK. A new ESC (as long as it has 100% reverse power) would be better than the 104 he has now.
I have to say, that is a really poor design decision right there. Imagine the design meeting discussion for the TEU-104BK: "Yes, let's make reverse 50% as powerful as forward. Oh, and while we're at it, let's do the same for the brakes but we won't tell anyone!" I thought the MOSFETs used for reverse were separate from the ones used for brakes, but maybe I'm wrong. If they were separate, I'd think Tamiya could have kept 100% brakes and 50% reverse.
Would this be the reason that the TEU-101BK was issued to the Buggy Champ and Sand Scorcher, or was it simply because they were released before the TEU-104BK was developed? The above information makes a lot of sense - I have had braking on my Buggy Champ (with the kit-issued TEU-101BK) approaching, if not really equaling, that on some of my other cars equipped with the TEU-104BK.
I actually thought the TEU-104BK was the ESC added to the Buggy Champ and Sand Scorcher kits. Tamiya do not supply ESCs in the kits unless it's an XB RTR model. The ESCs are added by distributors (and they whack a sticker on the box and shrink wrap it). It may have been that the distributors had excess TEU-101BK's at the Buggy Champ release and included them instead of the TEU-104BKs.
With the re-re SRB being intended to use Tamiya's smaller Li-FE LF1100 packs, the TEU-104BK ESC has a cutoff built in suitable for Li-FE packs (5.0v). It's a shame they changed the specification, and didn't leave it the same 100% forward and 100% reverse as the TEU-101BK, when they included the Li-FE cutoff.