Almax series 3 + derbi Teresa's set top box = real concern??

[Ottocle]

My series 3 Almax arrived today. I want to be able to commute with it but it weighs 8.6 kg and I also have an Abloy 362 padlock which weighs another 1.4 kg.

I'm looking at a givi monolock top box with a max weight limit of 10kg. What happens if I exceed that 10kg?

I am going to get a Derbi Terra to begin with. Can a 125(albeit a large on) handle that much weight on its rear in a top box?

[Tungtvann]

The top box will explode into a million pieces if you exceed its' weight limit.

[CaNsA]

[Pol Anorl]

LOl.
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[Pol Anorl]

LOl.
____________________
GOOD GAME BODYGUARD: https://i.imgur.com/8WePGgf.jpg
20:30:37 Pyro.: I don't sort of like men, I take every advantage to choke on dick.
Jewlio Iglesias: You live in Liverpool - Chances are, the front door has already been kicked off the hinges

[DottyDuck]

you will end up wheelie-ing everywhere.
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CBT- 2012 Theory- 18/12/13 Mod 1- 07/01/14 Mod 2- 15/01/14
Old Bike: Zontes Panther 125cc - wrote off Current Bike: Kawasaki ZR7

[Sako]

https://www.fdwallpapers.com/misc/images/nuclear-mushroom-cloud.jpg

[Nexus Icon]

The Derbi will cope. Great bike.
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Greetings from Shitsville!

[stinkwheel]

My oppinion.

1) The bike is designed to have two people on it. You have one plus a chain. If you find it's making the front end go light, keep it in a bag strapped to the pillion seat instead.

2) The 10kg limit is the safe working load. So it'll carry at a minimum three times that before it breaks. Manufacturers are also paranoid. My sports rack states a maximum load of 2.5kg. I've had 25kg sacks of coal on them + luggage before today.

Now for some maths.

The surface area of a monolock topbox is 300x400mm so 0.12 square metres.

Your bike will be able to do maybe 70mph flat out. 31.3m/s

So. Aerodynamic drag = 0.5 x mass density of air (1.204 @ 20 degrees) x speed squared x drag coefficient (lets charitably call it a half sphere and allow 0.42) x area

= 0.5 x 1.204 x 979.7 x 0.42 x 0.12
= 29.72 Newtons. An equivalent of 2.97kg of force.

Not so much eh? But wait, speed was squared. Push it to 100mph? Any halfway decent sports tourer with a Givi box will be doing that along a German Autobahn. Now 6.1kg

TL;DR
A bike doing 100mph will be putting slightly over 3kg more load on the box purely in terms of aerodynamic drag than your bike going flat out.
____________________
“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[Ottocle]

Thanks - that helps. I didn't really get the maths bit; also make allowances for drag (an extra couple of kgs) was what I got. Good that there's some reliable info on here.

[stinkwheel]