Auxillary Fuel Tank Installed!

[Dudley]

OK, I will post one more time. I sent the information to a friend of mine to calculate the physics of this mod. He spent the last 20 years teaching physics. This is what he wrote back:

The answer can only be approximated because there is no coefficient of friction or air resistance and we don't know the rate of negative acceleration. Assuming it is instantaneous:

70 mph *5280/3600 = 102.67 ft/sec If the keg weighs 40 lbs then the total instantaneous force would be 102.67 ft/sec * 40 lbs = 4106.8 ftLbs/sec

Divide that by the number of straps, each strap would have to hold 4106.8 / 2 = 2053.4 lbs


Do you still want this on your back? That's up to you. Looks like I was about 3950 footpounds off.

 

[bone crusher]

OK, I will post one more time. I sent the information to a friend of mine to calculate the physics of this mod. He spent the last 20 years teaching physics. This is what he wrote back:

The answer can only be approximated because there is no coefficient of friction or air resistance and we don't know the rate of negative acceleration. Assuming it is instantaneous:

70 mph *5280/3600 = 102.67 ft/sec If the keg weighs 40 lbs then the total instantaneous force would be 102.67 ft/sec * 40 lbs = 4106.8 ftLbs/sec

Divide that by the number of straps, each strap would have to hold 4106.8 / 2 = 2053.4 lbs


Do you still want this on your back? That's up to you. Looks like I was about 1900 footpounds off.

Interesting...got through calc. based physics but didn't enjoy it too much...one thing to note is that this also doesn't take into effect the wear and tear on the restraining system...this will weaken it over time...

 

[Dudley]

I don't get why some have to take a poke at a guy who is solving a problem for himself.

.

I am not taking a poke at him. I am just trying to make him aware of the dangers of what he is doing. If I didn't care I would just have read it and gone on. But as a fellow Spyder Ryder, I cannot in good conscience ignore what he is doing and warn him of the dangers. If he decides to go ahead, then I have done my part.

 

[Firefly]

And does anyone know if the straps are unable to hold 2000 lbs? Realize it would only be for milliseconds.

I don't see the same concern for people mounting various bags on the rear rack or back seat using bungee cords - not to mention that this same rack unit is holding the pressure of a passenger on it. Considering I don't know of any passengers that would weigh as low as this tank setup- think about the force put against the backrest from a 150lb. passenger.

I'd be more concerned about it not being grounded - but he says he's going to -

This isn't a mod that I would do - only because I don't do much long distance rides where I might run out of gas - but I think he's got a pretty decent setup. I didn't care for the other setup that someone out here did - with hoses hanging down, etc...

 

[dryheat]

OK, I will post one more time. I sent the information to a friend of mine to calculate the physics of this mod. He spent the last 20 years teaching physics. This is what he wrote back:

The answer can only be approximated because there is no coefficient of friction or air resistance and we don't know the rate of negative acceleration. Assuming it is instantaneous:

70 mph *5280/3600 = 102.67 ft/sec If the keg weighs 40 lbs then the total instantaneous force would be 102.67 ft/sec * 40 lbs = 4106.8 ftLbs/sec

Divide that by the number of straps, each strap would have to hold 4106.8 / 2 = 2053.4 lbs


Do you still want this on your back? That's up to you. Looks like I was about 3950 footpounds off.

The problem with the analysis is pretty obvious when you stop and think about it.... it assumes you just ran into a brick wall at 70mph. I think the possibility the rack might give way is the least of your problems. How about the impact a 130 lb passenger would have on you? ... or a 35 lb Givi tail pack?... or maybe a 25 lb dufflebag held down with a couple bungee cords? Normal... even panic stops won't generate anything close to these values, and a passenger will leave his/her seat long before you shear off (4) 5/16 bolts and/or (2) 1" wide 3/32 thick straps. I'm not any more concerned than anybody who attaches anything or anybody to their rack or rear seat. As for pressure build up in the tank due to heat... that's why they have vented caps or vent hoses.

Don't get me wrong, I/ we appreciate your concern... but we aren't couped up in cages, we are on open air rydes; and there are some risks we assume. Personally, I believe it's much more "dangerous" carrying a passenger than a 25 lb aux. tank; but you won't find me preaching abstinence to those who ride 2-up.

So let's all do our own thing... no need to get defensive or feel you must rationalize your views. After all, we're all in this to have fun.:f_spider:

 

[bone crusher]

And does anyone know if the straps are unable to hold 2000 lbs? Realize it would only be for milliseconds.

I don't see the same concern for people mounting various bags on the rear rack or back seat using bungee cords - not to mention that this same rack unit is holding the pressure of a passenger on it. Considering I don't know of any passengers that would weigh as low as this tank setup- think about the force put against the backrest from a 150lb. passenger.

I'd be more concerned about it not being grounded - but he says he's going to -

This isn't a mod that I would do - only because I don't do much long distance rides where I might run out of gas - but I think he's got a pretty decent setup. I didn't care for the other setup that someone out here did - with hoses hanging down, etc...

Just on this topic...the amount of time is not the only factor...it's the force generated in such...I'll give you an example...we know from studies that an 8mph rear-end collision creates up to 10G force in the cervical spine for only milliseconds...even though the range of motion of the neck in this timeframe is within your normal ROM, it will still tear tissue due to the fact that your soft tissues cannot accommodate to the forces in that short period of time.

This is a human model and studies support this...it's the distance and the time that matters for tensile strength of tissues...

I won't get into elastic, plastic, and viscoelastic properties of tissues here, but they all play in...

 

[bjt]

OK, I will post one more time. I sent the information to a friend of mine to calculate the physics of this mod. He spent the last 20 years teaching physics. This is what he wrote back:

The answer can only be approximated because there is no coefficient of friction or air resistance and we don't know the rate of negative acceleration. Assuming it is instantaneous:

70 mph *5280/3600 = 102.67 ft/sec If the keg weighs 40 lbs then the total instantaneous force would be 102.67 ft/sec * 40 lbs = 4106.8 ftLbs/sec

Divide that by the number of straps, each strap would have to hold 4106.8 / 2 = 2053.4 lbs


Do you still want this on your back? That's up to you. Looks like I was about 3950 footpounds off.

The problem with the analysis is pretty obvious when you stop and think about it.... it assumes you just ran into a brick wall at 70mph. I think the possibility the rack might give way is the least of your problems. How about the impact a 130 lb passenger would have on you? ... or a 35 lb Givi tail pack?... or maybe a 25 lb dufflebag held down with a couple bungee cords? Normal... even panic stops won't generate anything close to these values, and a passenger will leave his/her seat long before you shear off (4) 5/16 bolts and/or (2) 1" wide 3/32 thick straps. I'm not any more concerned than anybody who attaches anything or anybody to their rack or rear seat. As for pressure build up in the tank due to heat... that's why they have vented caps or vent hoses.

Don't get me wrong, I/ we appreciate your concern... but we aren't couped up in cages, we are on open air rydes; and there are some risks we assume. Personally, I believe it's much more "dangerous" carrying a passenger than a 25 lb aux. tank; but you won't find me preaching abstinence to those who ride 2-up.

So let's all do our own thing... no need to get defensive or feel you must rationalize your views. After all, we're all in this to have fun.:f_spider:

One thing I was thinking while reading this is who would care about anything on the back of the Spyder if they were riding the machine that encountered this immediate deceleration from 70 in the calculation?

If the rider weighs 150 and they are subject to the same force calculation (multiply by 102.67) they would experience 15,400 lbs. of instantaneous force. 200lbs? 20,534 lbs. of force. And my weight, 250lbs? 25,667 lbs. of force. No way anyone's arm strength even approaches what the strength of those two steel straps are. The rider would be ejected from the bike faster and probably farther than the aux. gas tank, rear bag, Givi topcase, etc.

 

[Firefly]

My thoughts exactly- If I hit a brick wall at 70mph, an aux fuel tank would be the least of my concerns.....

It looks like a nice mod- neat, clean, and functional. (and probably safer than the Pintos and the Corvair that I drove......):2thumbs:

Especially safer than when YOU were driving them-----:joke:

 

[Dudley]

Well, I have presented my concerns for this mod. It really doesn't matter to me that he will put this to personal use. I may be all wrong and all will work well. If that turns out to be the case, then I will gladly be wrong. All mathamatical calculaions are relative and subjective to discussions. The actual physical end result may be the only proof of a theory. I have tried to present my points of view on this project as has everyone else. Peace to all. Happy Trails and Ryde Safe.

 

[bone crusher]

Well, I have presented my concerns for this mod. It really doesn't matter to me that he will put this to personal use. I may be all wrong and all will work well. If that turns out to be the case, then I will gladly be wrong. All mathamatical calculaions are relative and subjective to discussions. The actual physical end result may be the only proof of a theory. I have tried to present my points of view on this project as has everyone else. Peace to all. Happy Trails and Ryde Safe.

This is/was a nice thread...one note...forget about hitting a wall at 70mph...you're more likely to get rear-ended...and being that is the case, who wants 40 lbs. of highly flammable fluid seated behind them?

 

[bjt]

This is/was a nice thread...one note...forget about hitting a wall at 70mph...you're more likely to get rear-ended...and being that is the case, who wants 40 lbs. of highly flammable fluid seated behind them?

As opposed to seated under them? :dontknow:

 

[Firefly]

I would also note that gas isn't a 'highly' flammable fluid. The vapor certainly is - but the fluid doesn't really burn that well .

Ever see a pop-up camper going down the road with propane tanks on the outside ? Far more 'flammable' product than gas.

 

[NancysToy]

As opposed to seated under them? :dontknow:

Amen!
-Scotty

 

[Firefly]

Well, I have presented my concerns for this mod. It really doesn't matter to me that he will put this to personal use. I may be all wrong and all will work well. If that turns out to be the case, then I will gladly be wrong. All mathamatical calculaions are relative and subjective to discussions. The actual physical end result may be the only proof of a theory. I have tried to present my points of view on this project as has everyone else. Peace to all. Happy Trails and Ryde Safe.

Okay - how about if he fills the tank up with some Royal Purple----- :joke:

You made many valid points and concerns-- nothing wrong with that at all!

 

[Lamonster]

Well, I have presented my concerns for this mod. It really doesn't matter to me that he will put this to personal use. I may be all wrong and all will work well. If that turns out to be the case, then I will gladly be wrong. All mathamatical calculaions are relative and subjective to discussions. The actual physical end result may be the only proof of a theory. I have tried to present my points of view on this project as has everyone else. Peace to all. Happy Trails and Ryde Safe.

 

[bjt]

Well, I have presented my concerns for this mod. It really doesn't matter to me that he will put this to personal use. I may be all wrong and all will work well. If that turns out to be the case, then I will gladly be wrong. All mathamatical calculaions are relative and subjective to discussions. The actual physical end result may be the only proof of a theory. I have tried to present my points of view on this project as has everyone else. Peace to all. Happy Trails and Ryde Safe.

Even though I don't agree with your concerns, I do appreciate you putting them on here. Bottom line is every mod isn't for everyone but everyone's opinions and views are appreciated (as long as they don't get nasty about it.) :thumbup:

 

[M2Wild]

Ya know, I was thinking that...someone is going to steal it, thinking it has beer in it...what a suprise that will be when they're pouring a cold one with a cigarette in their mouth...
:roflblack::roflblack::roflblack:

I wonder if cops are gonna pull them over thinking its a beer keg.

 

[bone crusher]

As opposed to seated under them? :dontknow:

Yeah, I'd say it's more protected under you in a frame as opposed to sitting on a seat behind you...bet it's been tested under your seat...

 

[bone crusher]

I would also note that gas isn't a 'highly' flammable fluid. The vapor certainly is - but the fluid doesn't really burn that well .

Ever see a pop-up camper going down the road with propane tanks on the outside ? Far more 'flammable' product than gas.

Where's there gas, there's gas...propane is kept in a vapor form...gas in a tank, when heated, will have more than enough explosive capabilities...

 

[bone crusher]

Even though I don't agree with your concerns, I do appreciate you putting them on here. Bottom line is every mod isn't for everyone but everyone's opinions and views are appreciated (as long as they don't get nasty about it.) :thumbup:

There's nothing wrong with being nasty, as long as you're nice about it!