Is there a technical reason that metal framed ebikes don't use the frame as a conductor, like cars do? Seems a logical way of reducing wiring looms.
Electrical Ground
- Thread starter fusion.wind
- Start date
I have always wondered this and assumed that it was down to safety - another layer of insulation between poles being a good thing.
It would be good to hear something definitive.
It would be good to hear something definitive.
The nearest I've ever seen to this is electrical feeds through the rear mudguard to supply the rear light. I suppose making connections to a thinwall frame in exposed conditions might bring problems, including corrosion and potentially electrolytic action between dissimilar metals.
As an aside on the car mention, not all have structural earth return. When FIAT sold their 124 to the Russians as the basis of the Lada it was heavily modified for Russian conditions, and one of the mods was cable earth returns. The stated reason was that Russia didn't have any auto-electricians but had many electricians ok with house wiring, so the car was made familiar to them.
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As an aside on the car mention, not all have structural earth return. When FIAT sold their 124 to the Russians as the basis of the Lada it was heavily modified for Russian conditions, and one of the mods was cable earth returns. The stated reason was that Russia didn't have any auto-electricians but had many electricians ok with house wiring, so the car was made familiar to them.
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Think it could be to do with the voltage being used. With a frame return, if no power was being drawn, then the frame would be sitting at battery voltage. This could be over 50V for a 48V battery. As someone who used to work in telephone exchanges, which in those days ran on 50v D.C., I can assure you that you don't want the experience of becoming the ground track for that. It can have very unfortunate effects on ones bowels.
Conversly it's hard to see where a circuit would be.
Second thoughts are that it's to do with avoiding the corrosion problems you get on chassis earth terminals.
Conversly it's hard to see where a circuit would be.
Second thoughts are that it's to do with avoiding the corrosion problems you get on chassis earth terminals.
Well, a carbon frame won't conduct, heavy steel isn't really used for e-bikes, and Aluminium isn't a great conductor - although aluminium is used for cheapness for very high voltage, very long run underground cabling for domestic/infrastructure power distribution etc. (but we're talking multiples of tens of thousands of volts and many miles distance).
Copper or silver is far more conductive/lower resistance/lower power loss where comparatively lower voltage and high current over short distances is required (but both metals would be far too soft to make a bicycle frame from!).
Copper or silver is far more conductive/lower resistance/lower power loss where comparatively lower voltage and high current over short distances is required (but both metals would be far too soft to make a bicycle frame from!).
Maybe an answer could be gold plating the frame?
Many e-bikes are priced as though they already have been.
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Not really so.. The arguement about carbon fibre is correct of course but I don't think that weighted much ( pun intended ) on the thnking of early electric bike designers. The aluminium would be ok for conductive purposes, it's not bad compared with copper only 30% worse. The problem is that it's hard to get a reliable long electrical connection with aluminium on a DC circuit as the metal oxidises whenever it can.
. But it has to do with both the number of circuits and where they are located. There is basically only one power circuit gong to the motor and it is typically physically removed from the rest of the bike , being say mounted on a hub. . Even the starter motor on a car has two leads going to it.. even is the return is just a short braided strap...
Incidentally have you ever tried to start a car with the strap disconnected?.... Things like the throttle cable get very hot as the current tries to find paths back....
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When you belong to a rowing club you quickly learn that CF conducts DC currents, so much so that rowing a CF boat or with CF oars is forbidden during thunderstorms...
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There's been a few anglers caught out too - the ones that use those 20ft poles on the canals. They can sometimes reach the overhead power lines.
https://www.researchgate.net/publication/304791856_CASES_OF_DEATH_DUE_TO_ELECTROCUTION_OF_FISHERMEN_USING_CARBON_FISHING_RODS_-_MORPHOLOGICAL_ASPECTS
https://www.mirror.co.uk/news/world-news/british-angler-is-killed-after-fishing-756240
Carbon would be classified as semiconductor, in the same segement of the periodic table as silicon, however it will never be as good as silicon in respect of doping and intrinsic resistance.. it's poor compared with any of the metals as a conductor about 300 times worse , if memory serves than copper...
Carbon fibre composite will have the lumps of poorly conducting carbon isolated by the resin, which insulates more.....
Those of us from a certain vintage, will recall carbon composition resistors , where soot mixed in various ratios with sand to make radio components. Also the delights of the carbon microphone, where granulated carbon was held in a capsule and the sound compressed and decompressed it, altering the resistance....
So not a good choice as an earth return...
Carbon fibre composite will have the lumps of poorly conducting carbon isolated by the resin, which insulates more.....
Those of us from a certain vintage, will recall carbon composition resistors , where soot mixed in various ratios with sand to make radio components. Also the delights of the carbon microphone, where granulated carbon was held in a capsule and the sound compressed and decompressed it, altering the resistance....
So not a good choice as an earth return...
Everything will conduct electricity to some degree, even materials we regard as insulating materials (glass, porcelain, plastics) because of their high resistivity. Messing about in a wet environment changes that resistivity/conductivity equation markedly. Surely the aim here is to conduct stored energy from the battery efficiently with minimal losses... for which you need a cost effective, low resistance, highly efficient conductor - copper is ideal. Aluminium as a carrier is IRO 60% as efficient as copper, and once oxidised, it can act as a pretty good insulator too; using an Aluminium bicycle frame as a return path is IMHO asking for trouble.
Sadly there have been several more.
Going back to 1985 when I was a Linesman's mate on Seeboard, I clearly recall several reported deaths. Very sad.
Weirdly, I have only seen this thread today, but was thinking about this very subject just yesterday. Once again I was taken back to 1985, when I my self received a 33kva shock. I was actually in a tree clearing power lines, and without thinking cut a very small branch, and stupidly lifted it over my head to throw it to the ground.
The inevitable happened, the branch touched the line, and all that I can recall is being thrown from the tree, and screaming uncontrollably on the ground.
The s**t hit the fan big time, as I had been on my own, and the guy that I was supposed to have been working with had bunked off early.
I recall going into the office after work, to be greeted by a deathly silence, and then a "what happened today?" Being young and smart I just said what do mean?
Apparently, a report had been telephoned in of me screaming, but the bigger issue was that I had tripped one of the two 33kva feeds to Tonbridge.
Beyond escaping the incident with my life and everything intact, I came very close to loosing my job, and the line had to repaired because it was burnt.
Not one of my best days of days at work!
11kva 'tickles' as we called them, were quite frequent when tree cutting, and we never really gave much thought to them. It was always when cutting pine trees on wet rainy days. You would be mid way through cutting, the chain saw would suddenly go slightly erratic, and the same time, you would feel a tingle. The trees weren't actually hitting the lines, just getting close.
What I did use to hate working on was LV lines 240v. LV used to scare the crap out of me.
My worst ever shock was from a 240v armoured cable feeding a shed. Rather than test that it was off, I just removed the fuse that fed it, only to discover after grabbing it, that someone had stolen a supply from a neighbour, and it was still live. My arms curled up tightly, every joint in my body locked, and pain hit my chest big time. Somehow I got away from it, but my hands were burnt, and my joints hurt for many weeks afterwards. All because I was being too lazy to carry out basic checks and procedure.
I put my hand into the fridge light socket to remove a blown bulb without unplugging the fridge. Someone had already removed it. Someone found me sitting on the floor on the other side of the kitchen...
LiPo can be fun too
LiPo can be fun too
I've lost count of how many times I've accidentally connected directly to 220/240 volt mains, but all that ever happens is a slight jolt, no pain or body movement.Sadly there have been several more.
Going back to 1985 when I was a Linesman's mate on Seeboard, I clearly recall several reported deaths. Very sad.
Weirdly, I have only seen this thread today, but was thinking about this very subject just yesterday. Once again I was taken back to 1985, when I my self received a 33kva shock. I was actually in a tree clearing power lines, and without thinking cut a very small branch, and stupidly lifted it over my head to throw it to the ground.
The inevitable happened, the branch touched the line, and all that I can recall is being thrown from the tree, and screaming uncontrollably on the ground.
The s**t hit the fan big time, as I had been on my own, and the guy that I was supposed to have been working with had bunked off early.
I recall going into the office after work, to be greeted by a deathly silence, and then a "what happened today?" Being young and smart I just said what do mean?
Apparently, a report had been telephoned in of me screaming, but the bigger issue was that I had tripped one of the two 33kva feeds to Tonbridge.
Beyond escaping the incident with my life and everything intact, I came very close to loosing my job, and the line had to repaired because it was burnt.
Not one of my best days of days at work!
11kva 'tickles' as we called them, were quite frequent when tree cutting, and we never really gave much thought to them. It was always when cutting pine trees on wet rainy days. You would be mid way through cutting, the chain saw would suddenly go slightly erratic, and the same time, you would feel a tingle. The trees weren't actually hitting the lines, just getting close.
What I did use to hate working on was LV lines 240v. LV used to scare the crap out of me.
My worst ever shock was from a 240v armoured cable feeding a shed. Rather than test that it was off, I just removed the fuse that fed it, only to discover after grabbing it, that someone had stolen a supply from a neighbour, and it was still live. My arms curled up tightly, every joint in my body locked, and pain hit my chest big time. Somehow I got away from it, but my hands were burnt, and my joints hurt for many weeks afterwards. All because I was being too lazy to carry out basic checks and procedure.
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I've just remembered another. When I was very little kid, I washed my cuddly toy, and put it straight onto one of those bar heaters. Apparently I got thrown across the room. Whether it is true or not I have no idea, as I was too young., but I guess that it is the sort of daft thing that I might have done!
In days gone by it was not unusual to dampen down the coal tire with a little pee before retiring for the Night .. not to be recommended with coal effect electric fires...I've just remembered another. When I was very little kid, I washed my cuddly toy, and put it straight onto one of those bar heaters. Apparently I got thrown across the room. Whether it is true or not I have no idea, as I was too young., but I guess that it is the sort of daft thing that I might have done!
It wasn't a direct connection then.. 230v accros the body , driving say 100 ma will cause all the muscle groups it contacts to contract violently. If a live wire is grasped by the hand, the contraction makes it impossible for the person to let go..if it were on the back of the hand, it would throw the arm away into safety...