Generator box mounting on rear bumper bar

Allyoops · Veteran Member

Generator box mounting on rear bumper bar

Baz421 · Guru

I hope you are going to insulate it a bit to dampen the noise.

IMHO these installations are the noisiest of all if sound attenuation is not addressed.

Hard rubber is not very good at sound attenuation.

Mark sure you use substantial (say 10mm) high tensile bolts, flat washers and nylock nuts to secure at there could be significant movement/vibration and you don't need this with a 20-30kg genny and box.

Crustie · Member

I would not mount it up against the rear wall, the slightest bump when parking or whatever will cause a lot of damage to your van,

I would put a few inches between,

Just a suggestion

Chris

TheHeaths · Guru

Adding 30 - 40 kgs to the back of the van is generally not considered to be a wise move, especially if the van has not been engineered to carry the additional weight.

At the least I would get someone (an engineer) to check whether the bumper can support the additional load, especially as it will be subject to quite large forces on less then perfect bitumen or dirt roads.

Perhaps see if the box could be added to the A frame instead to put the weight forward, rather than allowed to act as a pendulum at the rear of the van.

-- Edited by TheHeaths on Wednesday 9th of March 2016 07:52:52 AM

peter_s · Veteran Member

need to check how the box opens, I have one and the box needs at least an inch or two behind to allow the top to hinge back to open position

-- Edited by peter_s on Tuesday 8th of March 2016 11:16:57 PM

Yuglamron · Guru

I would just ask you to watch this short Video.

https://www.youtube.com/watch?v=PFzrWHTG5e8

Allyoops · Veteran Member

Thanks guys,
My van has a towball weight of around 280kg when loaded (227kg tare) so putting an extra load of 50kg on the A frame is not an option. The van has a sturdy well secured rear bumper and I was assured by the manufacture that another 50 kgs would be ok as this is about the same weight as having a second spare wheel on the bar which was an option I was given when purchasing the van. The box front and top lifts to open, pivoting via a piano hinge 100mm from the rear of the box thus when open the top of the box is clear of the van rearlight panel above box. Having the gennie at the rear of the van will also take a few kgs off the towball which will be an advantage. I intend to use the gennie out of the box to alleviate the noise issue but intend to look at sound insulation at a later date.
Thanks again for your input.

liz795 · Veteran Member

Allyoops
DS Custom Toolboxes -.Address: 34 Lara Way, Campbellfield Victoria 3061 They sell a great bracket
$90 check it out
Phone: 03 9357 5003

Baz421 · Guru

Yuglamron wrote:
I would just ask you to watch this short Video.

https://www.youtube.com/watch?v=PFzrWHTG5e8

I've seen this before and it's a good example on the principle of dynamic stability BUT the axle is about midway and the rear load exceeds the front load,,,, so it is designed to show excessive weight at rear with mid mounted axle,,, is it not???

Allyoops · Veteran Member

Baz just what i thought, the model on the video clip would always suffer from extra weight at the rear whereas my van will still have in excess of 250kgs on the ball as the van has the entry in front of the front axle which pushes the axle towards the rear rather than middle of the van.

Baz421 · Guru

Allyoops wrote:
Baz just what i thought, the model on the video clip would always suffer from extra weight at the rear whereas my van will still have in excess of 250kgs on the ball as the van has the entry in front of the front axle which pushes the axle towards the rear rather than middle of the van.

I used to work in an area where we approved or not approved these mods in the 90's I'll send you a PM as many people are so closed minded about this subject.

Peter_n_Margaret · Guru

Baz421 wrote:
I've seen this before and it's a good example on the principle of dynamic stability BUT the axle is about midway and the rear load exceeds the front load,,,, so it is designed to show excessive weight at rear with mid mounted axle,,, is it not???

No, it demonstrates yaw instability.

Imagine a bar with a 20kg load in the centre. You can pick it up via the weight with the bar horizontal and spin it around and stop it spinning easily.

Now imagine the weight as 10kg at each end, like a dumbbell.

Getting it spinning is harder and stopping it from pinning is very hard. In other words, controlling it is difficult because the yaw forces are many times higher.

For maximum stability and control, weight at the ends of a caravan are very bad, especially at the rear. Even if the "balance" is correct, the yaw stability may be very poor.

Cheers,

Peter

Baz421 · Guru

Peter_n_Margaret wrote:
Baz421 wrote:
I've seen this before and it's a good example on the principle of dynamic stability BUT the axle is about midway and the rear load exceeds the front load,,,, so it is designed to show excessive weight at rear with mid mounted axle,,, is it not???
No, it demonstrates yaw instability.
Imagine a bar with a 20kg load in the centre. You can pick it up via the weight with the bar horizontal and spin it around and stop it spinning easily.
Now imagine the weight as 10kg at each end, like a dumbbell.
Getting it spinning is harder and stopping it from pinning is very hard. In other words, controlling it is difficult because the yaw forces are many times higher.
For maximum stability and control, weight at the ends of a caravan are very bad, especially at the rear. Even if the "balance" is correct, the yaw stability may be very poor.

Cheers,
Peter

It's the dynamic (ie moving) forces ALL of them, to name a few mass , velocity, acceleration / deceleration thrust and drag, yaw, condition of suspension including and spring rates shock absorbers and tyre/wheel size road camber all contribute one way or another.

Also in the video you have to ask is the treadmill self driven OR are the car wheels providing the drive?

As you know if you loose control don't brake accelerate until rig is straight and under control.

Peter_n_Margaret · Guru

Baz421 wrote:
As you know if you loose control don't brake accelerate until rig is straight and under control.

And I consider it bad advise to put more energy into a system that is out of control.

Cheers,

Peter

rockylizard · Guru

Peter_n_Margaret wrote:
Baz421 wrote:
As you know if you loose control don't brake accelerate until rig is straight and under control.
And I consider it bad advise to put more energy into a system that is out of control.
Cheers,
Peter

Gday...

Decades ago advice used to be to accelerate to get a trailer (van) to stop swaying. Ultimately this lost favour as too many people were jack knifing their trailers and have lots of trauma. Accelerating the swaying trailer (van) frequently will only exaggerate the swaying.

The advice for correcting (controlling?) a trailer (van) should it begin to sway is to hold the steering steady dead-ahead and hold the accelerator steady - do not put your foot on the brake and do not take your foot off the accelerator. Then reach down and operate the manual slide on the trailer (van) electric brake so that the TRAILER's brakes are activated. This should bring the trailer (van) back into control.

Do NOT accelerate ... do NOT use the vehicle's brakes ... do NOT try to 'steer' your way out of it ... remain calm.

Cheers - John

Baz421 · Guru

rockylizard wrote:
Peter_n_Margaret wrote:
Baz421 wrote:
As you know if you loose control don't brake accelerate until rig is straight and under control.
And I consider it bad advise to put more energy into a system that is out of control.
Cheers,
Peter
Gday...
Decades ago advice used to be to accelerate to get a trailer (van) to stop swaying. Ultimately this lost favour as too many people were jack knifing their trailers and have lots of trauma. Accelerating the swaying trailer (van) frequently will only exaggerate the swaying.
The advice for correcting (controlling?) a trailer (van) should it begin to sway is to hold the steering steady dead-ahead and hold the accelerator steady - do not put your foot on the brake and do not take your foot off the accelerator. Then reach down and operate the manual slide on the trailer (van) electric brake so that the TRAILER's brakes are activated. This should bring the trailer (van) back into control.
Do NOT accelerate ... do NOT use the vehicle's brakes ... do NOT try to 'steer' your way out of it ... remain calm.
Cheers - John

Given that I used to teach drivers to jack knife AND recover semi trailers in the 70's as a part of driver training to get a licence, I have some knowledge.

We did this in practice not in an office mind you.

EDIT I also lost control (briefly) of 1/2 ton sand in a box trailer (the loader said the sand was wet, but it was dry and moved/slid to rear if trailer in one hit). Trailer wheels were over white line and into dirt as evidenced by tyre marks, if I didn't accelerate I believe I would have rolled. semi coming other way got off on dirt before we passed. Each sway increased in intensity and holding wheel straight had no effect at all. Acceleration straightened it pure and simple.

I take full responsibility for the miss load of trailer,,, never do it again.

-- Edited by Baz421 on Friday 11th of March 2016 04:21:07 PM

Aus-Kiwi · Guru

Do whatever . Feel the vehicle getting to know its limits at up to legal speed in safe place . Then just drive .. Being a keyboard warrior will get you nowhere ., it's mainly driving to conditions !!