Trailer brakes

[JonC]

6 hours ago, GPSguru said:

In its most basic form it is really just Newtons second law, which is F= m a.

However with a declining acceleration (retardation / deceleration) then the formula is more complex. I will post it up later.

I’m sure we are all on the edge of our chairs waiting for that. 

[GPSguru]

11 minutes ago, JonC said:

I’m sure we are all on the edge of our chairs waiting for that. 

Well, you should be, it is the same formula for wave acceleration and mass, so you can calculate at what deceleration rate is needed to avoid a wave over the stern !

[GPSguru]

@JonC, @Andy135 , @suzook12 , @Geoff

 

Here you go............

Decelerating mass is almost a sinusoidal function, which is why it is similar to wave mass calculation.

u(x, t) = 2a²·sech²(a(x + 4a²t))

u is the vertical displacement from equilibrium, t is time, x is horizontal distance and v is velocity,  sech(z) is the hyperbolic secant function and is equal to 2/(exp(z)+exp(−z)

 

[suzook12]

27 minutes ago, GPSguru said:

@JonC, @Andy135 , @suzook12 , @Geoff

 

Here you go............

Decelerating mass is almost a sinusoidal function, which is why it is similar to wave mass calculation.

u(x, t) = 2a²·sech²(a(x + 4a²t))

u is the vertical displacement from equilibrium, t is time, x is horizontal distance and v is velocity,  sech(z) is the hyperbolic secant function and is equal to 2/(exp(z)+exp(−z)

 

I often wondered......

What does that actually mean in real life?

[GPSguru]

5 minutes ago, suzook12 said:

I often wondered......

What does that actually mean in real life?

In simple terms ........

It means the quicker you slow with the tow vehicle, the trailer mass becomes greater, thus exerting more pressure on the brakes from the damped over-run actuator.

[suzook12]

5 minutes ago, GPSguru said:

In simple terms ........

It means the quicker you slow with the tow vehicle, the trailer mass becomes greater, thus exerting more pressure on the brakes from the damped over-run actuator.

Ok, now it makes sense. I pretty much knew that, just couldn't put it as simply as that

[Saintly Fish]

6 hours ago, GPSguru said:

@JonC, @Andy135 , @suzook12 , @Geoff

 

Here you go............

Decelerating mass is almost a sinusoidal function, which is why it is similar to wave mass calculation.

u(x, t) = 2a²·sech²(a(x + 4a²t))

u is the vertical displacement from equilibrium, t is time, x is horizontal distance and v is velocity,  sech(z) is the hyperbolic secant function and is equal to 2/(exp(z)+exp(−z)

 

I used to think that BK was the god of googling. But that takes it Ian....... top googling that man. 👍🏻

[Geoff]

8 hours ago, GPSguru said:

In simple terms ........

It means the quicker you slow with the tow vehicle, the trailer mass becomes greater, thus exerting more pressure on the brakes from the damped over-run actuator.

As you all know, my own school days and Newtons laws are now a long way off, but I do not think the trailer mass can change - forces yes, but mass? Geoff.

[GPSguru]

2 hours ago, Geoff said:

As you all know, my own school days and Newtons laws are now a long way off, but I do not think the trailer mass can change - forces yes, but mass? Geoff.

 

Yes, you are correct Geoff, the mass remains constant (because ' it is what it is') but the force is variable, but is there not another scientific name for it ? a 'something mass'

[Andy135]

3 minutes ago, GPSguru said:

a 'something mass'

You're thinking of Sunday mass. Definitely Sunday mass. 😁

[GPSguru]

4 hours ago, Saintly Fish said:

I used to think that BK was the god of googling. But that takes it Ian....... top googling that man. 👍🏻

 

🤣

It was more to illustrate that the forces of towing a trailer are definitely not simplistic. However, not the sort of complex math that I would remember without reference

TBF the only formulas I remember are those I used to use at work, like calculating my commission, formula based around satellite orbit, and several formulas related to Global positioning (GPS).

Google (and others) are a great resource, but you have to know what you are looking for as there is also a ton of shite on there. However, it beats going into the loft to find the right reference book.

 

[Odyssey]

But of course this is describing the forces by vector so a 2D representation. There will also be forces in the Z plane due to the windage from air currents caused by the towing vehicle and also vibrational forces due to the damping response of the tyres/axles. All of which will not be constant but periodic based on velocity. 
 

The long and short of it, fit new brakes, sell boat, get that new one out the Solent on the wrecks and catch something else than doggies 😉 

[Andy135]

1 minute ago, Odyssey said:

catch something else than doggies 😉 

But.... why....?? 🐶🐟🤣

[Odyssey]

1 hour ago, Andy135 said:

But.... why....?? 🐶🐟🤣

Better eating on pollack, keeps the kids happy so you can go out more often 😉 

[suzook12]

9 hours ago, GPSguru said:

 

something mass'

Kinetic?

[Gordmac]

22 hours ago, GPSguru said:

@JonC, @Andy135 , @suzook12 , @Geoff

 

Here you go............

Decelerating mass is almost a sinusoidal function, which is why it is similar to wave mass calculation.

u(x, t) = 2a²·sech²(a(x + 4a²t))

u is the vertical displacement from equilibrium, t is time, x is horizontal distance and v is velocity,  sech(z) is the hyperbolic secant function and is equal to 2/(exp(z)+exp(−z)

 

Something using hyperbolic functions, not too common! Used to teach shear diffusion that included them, too hard for the students so we dropped it. Not that I can remember any of it now.

From what I can remember from when I towed a fair bit the hitch damper was just that, stopped the trailer from hammering into the towbar under braking by damping the movement.

[GPSguru]

 

5 minutes ago, Gordmac said:

shear diffusion

As in liquids............ water, Oil, Blood etc ?

[Gordmac]

As in vehicle structures.

[Andy135]

Well done @GPSguru. Looks like your suggestion of the brake coupling was correct. I removed the coupling assembly then lo and behold...

I'll take the coupling assembly home to free off on the bench but it may need a replacement damper.

[GPSguru]

7 hours ago, Andy135 said:

Well done @GPSguru. Looks like your suggestion of the brake coupling was correct. I removed the coupling assembly then lo and behold...

I'll take the coupling assembly home to free off on the bench but it may need a replacement damper.

Excellent. However, you need a wallet warning as dampers tend to be expensive (£60 ish).

once stripped snd cleaned the coupling may be ok. Use lithium grease (wheel bearing grease ) for reassembly.

Edited April 24, 2021 by GPSguru

[suzook12]

I did ask if everthing was backed off.... Yes you said!!!!

Good it's sorted now........

[Andy135]

21 minutes ago, suzook12 said:

I did ask if everthing was backed off.... Yes you said!!!!

Good it's sorted now........

Oops! 🤦‍♂️

[GPSguru]

10 minutes ago, Andy135 said:

Oops! 🤦‍♂️

 

Does the stub axle have the alko 'one shot' nut ? ............... if so then it must be renewed and requires to be done up to 290nm to preload the bearing.

290nm is a fair bit more than 3 grunts and a hernia, I use a 350nm torque wrench.

[Andy135]

2 hours ago, GPSguru said:

 

Does the stub axle have the alko 'one shot' nut ? ............... if so then it must be renewed and requires to be done up to 290nm to preload the bearing.

290nm is a fair bit more than 3 grunts and a hernia, I use a 350nm torque wrench.

Yes. Have two new ones waiting in the wings plus torque wrench plus length of scaffold tube for the required leverage.

[JonC]

9 hours ago, suzook12 said:

I did ask if everthing was backed off.... Yes you said!!!!

Good it's sorted now........

I seem to remember you telling him to hit everything with a lump hammer, or at least you advised that on every other post to date.