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Old Oct 24, 2012, 08:08 AM
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cable brake vs. hydraulic brake vs. direct brake

hi all,

a question was raised about the possible advantages a hydraulic brake would have compared to a cable brake or direct brake

as i feel the thread in which the question was raised should not be "missused" for this discussion but i think the question is a very interessting one, i opened this new thread about the topic.

first of all you should know that i do 5th scale car racing since 15 years now and have wittnessed the move from cable brakes towards the hydraulic one. i have plenty experience.

i was allweays a fan of the calbe brakes and somehow "last man standing" until my car manufacturer stopped the production of their cable brake.

it took year until the hydraulic brake systems operated fine and without trouble. many people bought alot of different systems for a huge amount of money until a good hydro was produced.

once you have a system that operates fine and without any leaking or closing brakes due to heat, you will find out that the hydraulic brake has much more braking power but in the same way is less sensitive.

this is due to physiks and can only be solved with a spring in the servo lingage.

you devinitly need a volume balance inside the master cylinder.

to be continued
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Old Oct 24, 2012, 08:32 AM
Complete RC Idiot Savant
The Netherlands
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Originally Posted by Clark Wohlert View Post
you will find out that the hydraulic brake has much more braking power but in the same way is less sensitive.

this is due to physiks and can only be solved with a spring in the servo lingage.
I assume you use digital servo's? Try using an analog one.... They will act same like a spring when facing a heavy load like braking....

Brgds, Bert
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Old Oct 24, 2012, 09:26 AM
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@bert,

good point but from my point of view the war war with analog servos is finished............and they lost.
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Old Oct 24, 2012, 10:24 AM
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up to you of course....

I don't have the war, and never had. I use Digitals where they are needed, and use analogue where they still offer an advantage (and that is in MUCH more applications than you'd expect), and don't clutter things up by using a less suitable digital but needing to somehow compensate for the fact that digitals are not always the best solution (like for example at the brake but there are numerous more examples like that).

You would be amazed how many solutions are invented, for problems that would not have been a problem AT ALL, if analogue servo's were used, and then so for applications where digital servo's don't offer real advantages to begin with....

But that is just my personal opinion, and it absolutely does not mean, that digitals do not have their advantages.... Just not everywhere, and in my book, applications for analogue servo's still vastly outnumber those for digitals

Brgds, Bert
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Old Oct 24, 2012, 11:13 AM
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Originally Posted by Brutus1967 View Post
I use Digitals where they are needed, and use analogue where they still offer an advantage (and that is in MUCH more applications than you'd expect), ...
This is interesting. Please explain what is the difference between a digital and a analogue servo.
Then please tell me why that would make a change in how a brake works.
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Old Oct 24, 2012, 11:40 AM
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the digital servo tries to resist any force that it is faced with and stay in its selected position while the anlalog one will not do so.

maybe the analog one give an advantage but it does not really seem logical as the rotating tyre does not apply any force to the servo.

anyway, analog servos cannot operate with hrs transmitting mode and my futaba does not have a failsave option when operating in ppm mode.

i made my experience with not having a fine failsave last weekend and so ppm is not an option anymore
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Old Oct 24, 2012, 01:54 PM
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the problem of the hydraulic brake is the rigidity of the tube, causes serious problems in the steering system, with the direct brake this is not the case
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Old Oct 24, 2012, 02:46 PM
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Good point trame
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Old Oct 24, 2012, 04:48 PM
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Espaņa, CL, Ávila
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the problem of the hydraulic brake is the rigidity of the tube, causes serious problems in the steering system, with the direct brake this is not the case
+1



The tube rigidity is a big issue, unless you plan to:

1) Pass the tube through a hollow steering shaft, sure not 6mm dia. Jabbers feature bigger steering shafts?



2) Cut a new 6mm dia hollow steering shaft design (1.5mm bore) with brake line connectors in both ends.

3) Scale down all brake components and place them on the forks with no hidraulic connection with the rest of the bike (servo, pump and caliper on the forks, just servo wire connected to the bike)

4) Clark, you forgot to open the question about "electric brakes" too... But I canīt say more about this at this date.

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Old Oct 24, 2012, 07:44 PM
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Cable seems simple. Hydro at this scale would just upset me on a race day. lol.

As for reality....

When a rotor or pads gets hot it expands. Which causes for inconsistent pressure.

Hydraulic, I would think could apply it smoothly and the brake fluid could be compressed. In theory (in my head...lol, after a beer) I would trust the fluid to have a certain threshold before locking up the front end. Guess that is why ABS is so popular.

Cable as we know on Throttles is a no threshold on/off.

Best example i can come up with is everything full scale going to "fly by wire" acceleration. If you have the "shakes" the ECU will correct it.

LMK if im a rambling idiot?
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Old Oct 24, 2012, 10:43 PM
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...

LMK if im a rambling idiot?
Ummm - I think you know my opinion on that

-rskip
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Old Oct 25, 2012, 03:07 AM
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Originally Posted by trf_414_m2 View Post
+1



The tube rigidity is a big issue, unless you plan to:

1) Pass the tube through a hollow steering shaft, sure not 6mm dia. Jabbers feature bigger steering shafts?



2) Cut a new 6mm dia hollow steering shaft design (1.5mm bore) with brake line connectors in both ends.

3) Scale down all brake components and place them on the forks with no hidraulic connection with the rest of the bike (servo, pump and caliper on the forks, just servo wire connected to the bike)

4) Clark, you forgot to open the question about "electric brakes" too... But I canīt say more about this at this date.






I also tried these solutions but the pipe is too hard, for me the best system currently is the direct brake servo
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Old Oct 25, 2012, 09:01 AM
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Nancy, in France
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Quote:
Originally Posted by trf_414_m2 View Post
...
4) Clark, you forgot to open the question about "electric brakes" too... But I canīt say more about this at this date.
I've read that:
http://www.telma.com/produits/fonctionnement
Supermagnet Braking system - Working (1 min 37 sec)

and I had started to work about it with a special industrial disc:




The polarity of the 2 solenoid have to be inverted each other. The maximum amperage was 520mA; at high speed it brake not very good and at low speed it does not brake. The system is like an ABS, but in my case not brake enough
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Old Oct 25, 2012, 09:21 AM
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@lalain,

respect for that project.

in 5th scale racing we had a diff that worked in that way but it did not lock up hard enough to match toadays traction recomendation.

but anyway you have tried it and now you know more.

the problem with the hydros in pricipal is that the fliud is not to be compressed at all ans so your brake ist somehow like and on/off switch.
it is an issue with tha cars but it would be even worse with bike. we do not need the braking power those systems offer but we new a maximum of sensitivity.
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Old Oct 25, 2012, 10:55 AM
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Espaņa, CL, Ávila
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Lalain, my electric brake design is way different than yours...



Did you ever see these kind of quadcopter motors?



And how about the offset KP spokes for SB5/Roadies wheels?

My idea is to install one of these motors in the front/rear wheel hub and connect them to a small ESC each plugged to any channel with brake only.

This setup will act as an F1 KERS system and provide a slight charge to main lipo anytime you hit the brakes.

I know that almost ESC feature this function, but...

Did you ever think about the battery pack of a nitro bike?

I guess it could be much smaller because it would be charged at any slow corner, or getting much longer runs from same pack due to the KERS function.

No more pad fading, no more nitro fuel spills that ruin brake feeling, just programable brake tuning and go.

And maybe "all wheel drive" when 3rd brake channel gets linked to the 2nd channel throttle curve too.



Maybe available for 2013 season.

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