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Author Topic: Motorcycle petrol tank fuel gauge  (Read 6977 times)

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Offline djsb

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Motorcycle petrol tank fuel gauge
« on: August 17, 2010, 10:08:39 PM »
I have a motorcycle that does not have a fuel gauge. If I want to estimate fuel usage I need to zero my trip meter when filling up the tank and then take note at what distance I switch the petrol tap to reserve. At a busy petrol station I often forget to do this or just cant be bothered.
I'd like to fit some kind of gauge that gets it's reading either from fuel flow or some kind of sender in the tank. The tank is plastic and has a narrow fuel filler hole so access to the inside of the tank is going to be difficult. I know most car sender units use some kind of float to measure the fuel level. I've not seen any thing similar for motorcycles (but I havent looked too hard yet).
It would be great if there was a measureing device similar to that used in car wheels for tyre pressure. This is embedded in the wheel and is probably self powered. I've seen a few fuel flow projects on the internet for small aircraft. The only problem is the fuel flow sensor is too large or too expensive or both. Does anyone have any wisdom or ideas that I can persue. I'm not worried about the MCU side of things, the sticking point is using the appropriate fuel flow sensor.

Thanks,

David.
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Online mikeselectricstuff

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Re: Motorcycle petrol tank fuel gauge
« Reply #1 on: August 18, 2010, 12:47:27 AM »
I wonder if you could sense through the plastic wall, e.g. by change of dielectric constant or acoustic properties of the petrol inside - probably only practical for a few specific levels but might be useable. Is the plastic translucent ? If so an optical method may be viable.

Static pressure of fuel ? May not work when flowing, and may be issues with vibration, but potentially quite simple and accurate ( may need compensation of the pressure vs. content curve to correct for the profile of the tank).

Optical triangulation sensor in fuel cap?
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Offline djsb

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Re: Motorcycle petrol tank fuel gauge
« Reply #2 on: August 18, 2010, 01:17:47 AM »
Not sure if optical triangulation will work as the petrol is almost clear (pale to dark straw colour) and the inside of the tank is white/cream. The colour of the tank inside is useful as it will reflect light but only in a diffuse way. The tank is made of nylon and is painted dark red. I'm not sure if light can shine through it as I've not tried it.
There is an air vent under the tank, I wonder if air displacement could be measured in some way, just thinking out loud.
Or an air bubbler measurement system

Air bubbler (from wikipedia)

An air bubbler system uses a tube with an opening below the surface of the liquid level. A fixed flow of air is passed through the tube. Pressure in the tube is proportional to the depth (and density) of the liquid over the outlet of the tube.

Air bubbler systems contain no moving parts, making them suitable for measuring the level of sewage, drainage water, sewage sludge, night soil, or water with large quantities of suspended solids. The only part of the sensor that contacts the liquid is a bubble tube which is chemically compatible with the material whose level is to be measured. Since the point of measurement has no electrical components, the technique is a good choice for classified “Hazardous Areas”. The control portion of the system can be located safely away, with the pneumatic plumbing isolating the hazardous from the safe area.

Air bubbler systems are a good choice for open tanks at atmospheric pressure and can be built so that high-pressure air is routed through a bypass valve to dislodge solids that may clog the bubble tube. The technique is inherently “self-cleaning”. It is highly recommended for liquid level measurement applications where ultrasonic, float or microwave techniques have proved undependable.

David

P.S A picture of a similar tank

http://cgi.ebay.co.uk/MZ-MUZ-Skorpion-Sport-Cup-660-01-Fuel-Petrol-Tank-/390187062108?pt=UK_Motorcycle_Parts
« Last Edit: August 18, 2010, 02:15:14 AM by djsb »
David
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Offline Kiriakos-GR

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Re: Motorcycle petrol tank fuel gauge
« Reply #3 on: August 18, 2010, 01:20:48 AM »
Post an picture of your tank ..

Some times just the shape of it , does not help to add an gauge .

 

Offline rossmoffett

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Re: Motorcycle petrol tank fuel gauge
« Reply #4 on: August 28, 2010, 09:17:50 AM »
Maybe you're not concerned about this anymore because it's an old thread, but just FYI..

Fluid level is measured by ( density * gravity * height ) = ( pressure )

With 10 inches (25 cm) you're looking at only about 0.4 psi (2.75 kPa) or less for fuel pressure change.  You'll see much larger variations than that just from the fuel sloshing around or backpressure from the evaporating fuel.  Much larger changes than that will occur just from barometric pressure shift in absolute pressure gauges.  Air bubblers or pressure measurement on the outlet are out.

You're pretty well stuck with floats or dielectric measurement.

Another low-tech solution I see a lot in the oil/gas fields is an external measurement tube.  You could do that just by making a three-way outlet on the bottom, running a clear tube up above and back into the tank.
« Last Edit: August 28, 2010, 10:17:56 AM by rossmoffett »
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Offline Zad

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Re: Motorcycle petrol tank fuel gauge
« Reply #5 on: August 28, 2010, 09:37:12 AM »
My first reaction was to fit a pair of capacitative strips to the side of the tank, and measure the capacitance of the pair. Possibly by running it in an oscillator and measuring the oscillator frequency/period. It would need to be pretty sensitive though. I really wouldn't trust anything electrical inside the tank that wasn't custom made for the job.

Offline NiHaoMike

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Re: Motorcycle petrol tank fuel gauge
« Reply #6 on: August 28, 2010, 11:15:03 AM »
What about a self-heating PTC glued to the outside of the tank? It would get hotter if there isn't any fuel cooling it down.
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Offline Zad

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Re: Motorcycle petrol tank fuel gauge
« Reply #7 on: August 29, 2010, 03:00:13 AM »
That would only work for one point in the tank, and any sloshing would instantly cool it. Tricky things motorboke tanks, they aren't as linear as car tanks, and are even more prone to the fuel moving around.

Offline Koubek

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Re: Motorcycle petrol tank fuel gauge
« Reply #8 on: Today at 09:46:33 AM »
I was dealing with the measuring level of the petrol trough the hydrostatic pressure. With some kind of pressure sensors it is the working way. Only bigger problem was finding of the pressure sensor for reasonable price that can be used with petrol. Device worked as well as i decided to offer it for others. It was some years ago. I must do some advert for me  ^-^ Today i have an manufactory, this device is tuned into perfection and still in production.  😎 https://www.lskelectronics.com/fuelgaugepro1
I also described there some restrictions of this system so maybe it can also help to someone with constructing his own.
 


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