New class 31 loco 31190

Hello everyone,

I have been notified that the BVETMD team has now come up with the class 31. See their website to find out more.

May I just say, have fun with the vac brake variants... The braking really is slow on them!

Another fantastic piece of work from BVETMD. A very detailed cab with a nice authentic feel, excellent sound effects, and realistic performance.

The vacuum brake is interesting. Speed of application is quite slow, but about what I'd expect. The brake is in fact extremely powerful once you get it. The release of the brake is then agonisingly slow. The result is that for the first few stops you almost always end up stopping in a heap half way down the platform, and suffering the humiliation of having to re-take power to reach the platform end.

I don't have any experience with vacuum braked stock on the real thing, so I can't say whether the above is accurate. Vacuum brakes are certainly slow to release (nature abhors a vacuum, after all...) but are they THAT slow? I'll leave someone with more knowledge than me to comment.

Either way, the braking is great fun, and the loco overall is superb. Extra marks from me for the cab being wide enough to work well on a wide-screen monitor.

Thank you to all at BVETMD.

James

I've never actually driven anything with vac brakes, but have been in the cab/watched the gauge in the guards carriage etc. And it does seem that they are actually that slow.

Also Martin is one of a group, who own a class 46 based at the GCRN preserved railway, and he used to be one of the main diesel drivers based at the Llangollen Railway. So I trust his decision, down to his experience!

RE- vac brakes.
Just thought I'd clear things up a little so here goes.

The length of time it takes for the brake to apply/release is largely dependant on the amount of braked vehicles in the consist. For example, if you have a long train behind, it will take longer for the brake to apply down the length of the train as the vacuum is slowly destroyed. This obviously applies to the release time also as the loco's exhauster has to then re-create the vacuum along the train pipe. Remember, vacuum brakes rely on one single pipe along the whole length of the train and once a brake application is made, it literally will take an amount of time to propagate from the front vehicle to the rearmost vehicle. Although with a longer train there is more brake force available so once the brake starts to bite it will come in with considerable more force.
However, on the prototype, there is a 'release' position on the drivers brake valve which is sprung held to the left of the normal 'running' position, which actually speeds up the exhauster/s motor, thus creating vacuum quicker than normal. This is used in situations where a driver will need to -re-create vacuum quickly in order for a quick brake release, however, BVE is not capable of simulating this at present so you are stuck with just the normal release speed.
Also, on the prototypes, with both vacuum and air brakes, there are set values at which a driver cannot take power if the brakes are partially applied. In the case of vacuum brakes, a device called the vacuum governor will prevent power from being taken until the brakes have released to 15in HG on the vac train pipe. Adversely, power is also cut off when the train pipe is dropped to 12.5in HG. Again, BVE cannot simulate this at present.

There are two main things to remember when running vac braked stock,

1- Wherever possible come to a stand on a rising (releasing) brake.
2- Give yourself plenty of time - this is very important and was the thing I would constantly drum into trainees heads when I was instructing on various traction, always allow plenty of time for the brake to react to your needs. The most common mistake with vac brakes is making an application, then realising nothing is happening, so your natural reaction is to brake more, then all of a sudden you realise that once the brakes start to kick in you have totally overcooked the vacuum and have stopped well short of where you need to be as you cant re-create the vacuum in time.

Maybe I should do a Youtube video demonstrating the necessary techniques ?
The new version of the class 50 will be ideal for this so if folk want me to do this then speak up.......

Maybe I should do a Youtube video demonstrating the necessary techniques ?

That sounds like a very good idea! I imagine a lot of driving techniques on older stock are much different from the latest machinery.

Yes Martin. I think seeing the proper technic would be great. I think I've got it, from watching drivers on pres lines 'see-sawing' the brake handle etc.

But a detailed explanation would be great too.

Agreed, a tutorial would be interesting. Like Pedned, I think I'm just about there with it, but I sometimes worry with BVE that people give up with the more difficult to drive trains (like the vacuum brake 31, and the First Generation DMUs) and just drive the straightforward ones, for lack of guidance. If more people can get into something more complex, it's a whole new dimension to the game.

My only other question about the 31's brake is whether the four steps are correct, or is it a stepless brake in reality?

No steps as such James, though from the running position the valve is marked 'initial', 1st application, then 'full service' and 'emergency'.
On moving the valve to the initial position, if correctly set, the vacuum will drop to around 15in HG, giving a very slight brake application, this is sometimes known as 'setting the brake', whereby any slack in the brake linkages is taken up and the brake blocks are gently rubbing on the wheelsets. It is good practice on the prototype to try not to allow the brake to release above this setting as if this happens there will be more of a delay next time you demand more braking effort, as you will have to take up any slack in the system once again, if that makes sense.
As you say though, the valve gives a totally gradual control of vacuum, in other words, the more you move it forward the larger the drop in vacuum.
Theres four steps on the 31 just to try and make life a little easier and to get a fairly realistic drop in vacuum for each setting thats all.
Without going into the technicalities too much, the train brake valve on a dual braked loco actually controls the vacuum by dropping the air brake pipe. I know this sounds confusing but this is how it actually works, the drop in air train pipe pressure controls the drop in vacuum via a device called an 'air/vac relay valve' or AV2 valve. The only time the drivers brake valve controls the vacuum directly is when it is placed into the emergency position, which in turn opens a flap on the valve and vents the vacuum directly to atmosphere.
Hope this makes some sense James.

Martin, I think some real life driver training may be required from you!

Thanks Martin, very interesting. A colleague of mine once destroyed a set of buffer stops due to a faulty AV2 valve (or that's what he claims....) so it's interesting to have some technical explanation.

Incidentally (my having seen Pedned's comments) - any chance of a '46' (fantastic machines) turning up in BVE TMD one day....?

Maybe one day, the cabs on 010 arent really in good enough nick at present but I could possibly do a sister loco. Theres other stuff in the pipeline first though

Please tell me it will involve a 37240 sound set!
Haven't had it for a few years, but I remember it being a bit of a Monster, especially through Berwyn Tunnel... But then again had a few hellfire runs with you driving 20142 as well Martin!!!

had a few hellfire runs with you driving 20142 as well Martin!!!

you should have come up and said hello then Jamie !
That thing had to be driven flat out at Llan otherwise it wouldnt get up the hill !

bvetmd wrote:

had a few hellfire runs with you driving 20142 as well Martin!!!

you should have come up and said hello then Jamie !

Apart from last year for 31162, I haven't been to Llan since 2006...

Its likely that I'll never visit the place again
A dying railway I'm afraid buts thats only my opinion......

Back to topic anyway, I'll put a vacuum braking tutorial in the class 50 up online in the next couple of days all being well.

Unfortunatly a lot of railways are going that way. With funding running out and less and less volunteers being able to get out to work on the locos and railways... etc. The recession has taken its toll on what is a very niche market.

bvetmd wrote:
Back to topic anyway, I'll put a vacuum braking tutorial in the class 50 up online in the next couple of days all being well.

I look forward to it.