Pneumatic Axle Brake Design

[MxWinters]

Hey everyone, today I would like to share with you a design for a pneumatic axle brake. I had intended on using this on the cab unit for my artic lorry (semi truck) as the 2 speed gearbox I had in it had a neutral position. The 4 speed sequential gearbox designed by Sariel that I am using now, doesn't have a neutral position so I will simply use the drive motors as a parking brake. However, I do plan on using this air brake for the trailers.



The axle/differential is something your familiar with and this air brake is more-less an addon. Just like most real air brakes, air pressure is required to release it. This was designed for a ~1:16th scale lorry and is 2 1/2 studs from the rear of the axle frame but the basic principle could be made bigger and used for other creations other than a vehicles.



When using this design on a vehicle, it should be noted that this brake works on the differential and not the wheels, therefore it this is not a perfect braking system, the wheels can still slip causing the vehicle to move. Thus I don't recommend using this with living Minifigs. This air brake won't always release evenly causing added fraction on the axle from one of the double half liftarms remaining in contact with the pulley's tire, however there are serveral options for overcoming this such as routing the air lines in such a way that brake does release properly. When applying this air brake, its best to only supply air to the ram for a short time, as the ram doesn't ever fully retract, air will leak if you leave the valve open. This isn't really an issue when the brake it released.

I won't claim that this is completely my design but I don't ever recall seeing this online and have searched for similar designs but didn't find any. If this is someone elses design than I'm sorry for posting this, mods please take this down if that is appropriate.

Not sure if I can post the LDD file for this to this forum but if you need it, I can post it to my Google Drive account if it is allowed.

Hope you like it, let me know what you think.
Take Care
Morgan

Edited September 12, 2019 by MxWinters

[Jurss]

Interesting design

1. I would out there 5L beam

2. I would put there some bracing, so that by braking it wont go up.

 

3. I would remake so, that rubber or some shock absorber works on releasing brakes, so that there is no need to always have pressure.

[TeamThrifty]

1 hour ago, Jurss said:

so that there is no need to always have pressure

This is how real air brakes work though... no pressure and the brake is applied, for realism, it think this is the right solution...

[brickless_kiwi]

A lot of the light weight Japanese trucks have the simple system of a drum brake on the back of the gearbox that simply locks the driveshaft to the axles as a park brake. the only issue with it is a lot of drivers tend to apply it at speed with weight on and given that its a standard drum brake with a sheet metal backing it tends to poop itself.

[TeamThrifty]

i think its a safety feature - if the air system fails, the brakes default to on. better than the other way round! arriving at a corner and finding you have no brakes...

[Yevhen]

Isn't the mechanism too complicated for such a minor function? Why to use a pneumatic system?

[Jurss]

5 hours ago, TeamThrifty said:

This is how real air brakes work though...

Yes, there are reasons for that, but for lego model I think opposite solution will be better - then brakes could be engaged just by starting compressor, not running it all the time, and also using separate motor for pneumatic valve. Yes, they could be then slower ...

[MxWinters]

On 9/11/2018 at 6:27 AM, Jurss said:

Interesting design

1. I would out there 5L beam

2. I would put there some bracing, so that by braking it wont go up.

 

3. I would remake so, that rubber or some shock absorber works on releasing brakes, so that there is no need to always have pressure.

Sorry I'm not sure quite what you mean on your first two points, would you mind expanding upon them.
On your third point, see below for my reply.

 

On 9/11/2018 at 8:01 AM, TeamThrifty said:

This is how real air brakes work though... no pressure and the brake is applied, for realism, it think this is the right solution...

 

On 9/11/2018 at 9:38 AM, TeamThrifty said:

i think its a safety feature - if the air system fails, the brakes default to on. better than the other way round! arriving at a corner and finding you have no brakes...

 

On 9/11/2018 at 1:37 PM, Jurss said:

Yes, there are reasons for that, but for lego model I think opposite solution will be better - then brakes could be engaged just by starting compressor, not running it all the time, and also using separate motor for pneumatic valve. Yes, they could be then slower ...

I also believe most air brakes require air to release for safety, I think its the same for rail stock, both for positive and negitive air pressure braking systems, at least in the UK anyway. I also think that this is the better method for my model. I plan on fitting an auto-compressor and air tank under the trailer of my artic lorry as the trailer will have pneumatic suspension which will require air pressure. Regardless, the air compressor doesn't need to be running continuously anyway, once you apply air and release the brake, you can just close the value again and the brake will stay released untill most of the air in the ram and air lines leaks out. This wont happen within 5 seconds of releasing the brake thus there is no need for the compressor to anyways be running.
 

On 9/11/2018 at 1:26 PM, Yevhen said:

Isn't the mechanism too complicated for such a minor function? Why to use a pneumatic system?

I don't think its that complex. Its 84 parts including diff and axles. This will be an important feature on my lorry as I will be parking the trailers on hills and since I will be using wheels on the landing gear rather than a flat plate/tile, I don't want the trailer rolling down a hill. Mainly due the suspension on the trailer will be pneumatic and I rather have air lines going between trailers instead of unrealistic flat wires. Just remember, I built this for my lorry which I'm building in a very particular way and due to curtain specifications and design choices, I think that this is the best solution for my model. I'm open to ideas and if I see a better braking system that will fit into my design, Ill happily use it. Also I prefer to flick a valve then applying the brake electrically or manually.

Ive posted the LDD file for this on my Google Drive account if you want to download and look at it properly, hopefully I'm allowed to post this link, really sorry if I'm not:
https://bit.ly/2kcF9h1

Take Care
Morgan

Edited September 12, 2019 by MxWinters

[Jurss]

7 hours ago, MxWinters said:

Sorry I'm not sure quite what you mean on your first two points, would you mind expanding upon them.

See where I put those numbers on picture.

[1974]

TLG experiemented with this ages ago (IDEA Book 8889 from 1984) :

[TeamThrifty]

19 hours ago, Yevhen said:

Isn't the mechanism too complicated for such a minor function?

Surely this is the point of technic?! Complex problem solving is where the pleasure comes from... whether its minor or major function. I've seen moc's (crowkiller maybe?) where there were pneumatic drum brakes on each wheel... he was congratulated on that (and rightly so), no one said it was too complicated then....   

[MangaNOID]

I like this. Although I tried some braking on a pulley wheel also with the rubber ‘tyre’ and the  ‘tyre’ slipped a lot on the pulley wheel when grabbed. Have you not had this problem I guess? I was using high rpm though which maybe different to what you have.

make sure you post the finished arctic truck!

[MxWinters]

18 hours ago, 1974 said:

TLG experiemented with this ages ago (IDEA Book 8889 from 1984) :

Interesting, I've not seen that book. That idea is similar in principle but quite primitive (expected for 1984). It does only have a single contact point but it does work on each wheel and not the differential. Thanks for showing that to me :D
 

16 hours ago, TeamThrifty said:

Surely this is the point of technic?! Complex problem solving is where the pleasure comes from... whether its minor or major function. I've seen moc's (crowkiller maybe?) where there were pneumatic drum brakes on each wheel... he was congratulated on that (and rightly so), no one said it was too complicated then....   

I completely agree, I can't fit drums on each wheel, due to the size limitations. If I was building my lorry in 1:10 scale, it wouldn't be an issue but 1:16 is a little too small for individual brakes on each wheel. This axle brake is my next best option.
 

10 hours ago, MangaNOID said:

I like this. Although I tried some braking on a pulley wheel also with the rubber ‘tyre’ and the  ‘tyre’ slipped a lot on the pulley wheel when grabbed. Have you not had this problem I guess? I was using high rpm though which maybe different to what you have.

make sure you post the finished arctic truck!

Interesting, I shall have to keep this in mind and make sure this doesn't happen, thanks for making me aware of this. I have only tested this on my proto-type lorry and it worked well, but that was just a test model and only weighed about 1-1.5Kg so I don't really consider those tests to be totally accurate. The high speed could be the reason for your design was slipping. With my current lorry, the wheels only spin at 3RPM in first gear and 15RPM in fourth gear, the differential's 20 tooth pinion gear and thus the pulley spins a little faster but not by much.

I should just point out, I'm not building an "arctic" lorry. The term "artic lorry" is a British phrase which is short for articulated lorry. Most places tend to call them semi trucks. An artic lorry is just like a normal semi truck is that it is designed to drive on smooth tarmac roads, it has nothing to do with the arctic or vehicles designed to drive on snow/ice. Sorry for the confusion.
Regardless, don't worry, I will start a new thread for my lorry when I've ironed out a couple of issue it has.

Take Care
Morgan

[1974]

Well it does work rather nicely, the steering not so much

It's true that brake locking on trucks, trains etc are always "on" and it's the air (pneumatic parts) that keeps it off. In case of failure (lack of air) the brakes will lock. Hopefully

Cheers,

Ole