Atlas Questions

Vince said:
I am hoping they have one of their pressure-sensing tank caps that fit. They do a blurb about a patented petrol cap with the ability to only breathe when it reaches a pressure threshold reducing fumes into the environment. I tried pasting but the site wouldn't do a copy. Hope it doesn't strangle the engine. The blurb is at the front of the catalogue.
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Is the urea bit for when you need a pee? Must be uncomfortable riding around with that in your Y fronts.

Paul
 
Vince said:
I am hoping they have one of their pressure-sensing tank caps that fit.
Click to expand...
I doubt that they'd be suitable for bikes Vince. You're right to be concerned about it strangling the engine.

The diagram of the fuel cap shows separate valves. One for inward venting and one for outward venting. They list caps suitable for a whole bunch of cars, but none for motorcycles. The difference between car and bike fuel systems is that cars have fuel pumps whereas motorcycles are gravity fed.

The opening pressure for the tank vent inlet valve would need to be set at pretty much zero KPa* (see note below) so as not to cause fuel starvation on a bike. Whereas a car's fuel pump would be able to overcome a much higher suction pressure at the pump inlet.

The outward vent only needs to be set at a pressure low enough to stop the tank from over-pressurising on a hot day.

If you're considering getting one of those caps for a bike, you'd need to ask if they do a version suitable for gravity fuel feed.
The cap profile is pretty high too, which might interfere with your plan for a tank bag.


* Note: Static head pressure for fuel is about 10 KPa per metre depth. So if a full tank on a bike has a fuel level 300mm above the carby, the static head of fuel pressure at the carby's float valve would be about 3 KPa. As the fuel level drops, the pressure will decrease. Even as little as 1 KPa vacuum in the tank could prevent fuel flowing under gravity if the level in the tank was low.
To get your head around KPa, remember that a tyre pressure of 30 psi is a bit over 200 KPa. You could probably fart at 1 KPa.
 
Now why would you suspect that? The Aserbus lockable tank cap had a hoseless inbuilt breather like my Pantah has plus the std Laverda cap. To be honest I have no interest in it being lockable, just hoseless. Those car ones look to be well overkill, maybe they just do one with a less complicated inbuilt breather with no hose. Chances are I never hear back from them anyway. I do find it odd, older bikes usually don't have any breather hoses but all of a sudden they run cap hoses or tank-top-mounted hoses like modern Ducatis. Bet its some USA DOT regulation to sell there. All good as it just adds to my knowledge base. Wouldn't it be good to be able to just buy a strap-on tank bag and ride the bloody thing?
 
Got it all wrong, Vince.

A hose off the fuel cap just looks cool... :rolleyes:

Also a lot cheaper than devising a breather system that is invisible AND works.

piet
 
It looks like I have found a strap-on tank bag that will work with the tank shape and not crush the fuel tank cap breather, it has an opening in its mounting base and a raised cavity that clears the cap and breath hose and is probably the most waterproof available. But as usual, it's pretty close to perfect and eye wateringly expensive. Plus one of the specialist local Adventure Bike shops has both models in stock to be sure it fits the bike and is big enough to hold the crap I carry but not too big to get in the way. Once the annoying fuel tap weep is fixed and I have this bag fitted I can ride the bloody thing for a comfortable full day at last. I hope.
 
There are 2 models of Giant Loop Tank bags that have a raised section in their base that looks to clear the tank filler cap and hose enough to not pinch that hose off. The slightly smaller one is called The Diablo and the slightly bigger one is called The Fandango and that's what I bought. I have a Thermos-style water container that's 340mm long and I want it to fit. They list their vertical and horizontal sizes but as their bags slope down the tank at an angle I drew a scaled drawing to see this sloped size and I am hopeful the thermos will fit, plus I checked this folded and stapled 3D template on the bike and it looks good I think fingers crossed. The other unknown is how the single around the steering head and the 2 rear straps will fit as there isn't much of a gap past the tank for these. Will know next week when it arrives. They are a lot more water resistant than most other bags but the downside is cost. BTW they are the most expensive tank bags on the market but the place I bought them from is by far the cheap I have found in Oz, I am talking $100 cheaper than most others. A lot of places don't have stock but will sell you a product at $100 more and then order it from the USA and then send it to you, this place had stock plus free postage in Oz. Great service, I did go to High School with the owner but he wouldn't remember me from decades ago. He is a pretty famous ex-works Endro racer Jeff Ballard.

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Looks like a good product Vince. Just looking at the dimensions. Seems pretty roomy but that's a bloody big water bottle you've got. I reckon it might be a bit of a squeeze. I think we should be taking bets on whether it'll fit. I'm guessing no. Not without pushing the bag all out of shape anyway.

I suppose you can always get a smaller bottle if it won't go in. I just use a recycled plastic soft drink style bottle with a screw-top cap. They're pretty robust if they get scrunched up against tools and other shit. I'm not fussy about thermal insulation. Warm water is just as good for rehydration as cold water.
 
I got sick of having water on hot days become warm in minutes, the 2-litre thermos keeps it cold for a couple of days and I just buy a 600ml cold bottle and add it as I drink it. I use a fully vented jacket but still get dehydrated really quickly if it's over 30c. Didnt bother me when I was younger but it does now. A few years ago I got Heat Exhaustion and close to heat stroke according to my GP on a multi-day job in high 40c weather, even drinking mega litres a day. I don't miss working for the Insane Architect any more. It was BAD, I lost quite a lot of Kidney Function according to the blood test and was close to muscle meltdown. It took a good week to come good, and no permanent Kidney Damage and I thought I had it under control. So I take extra care these days.
 
To me, it's about cooling your core. I used to just shake my head when my Nan would say how refreshing a nice hot cup of tea was on a 40c-plus day while she cooked on a wood stove in a room with no open windows. Years later she had air conditioning but didn't like feeling a cool breeze so would turn it off.
 
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