Here seems a good place to ask a few questions on my mind:
My previous post about designing/building a small pedal assisted electric vehicle makes me ponder a few questions which some folk here might have the answers to:
Anyone suggestions on tyres, I'm after something off the shelf which is solid (And thus puncture proof.) yet has good road grip and long life. As my experience of testing various brands on my existing cycle shows them to wear out quickly, and have very poor grip, not to mention difficulty in staying on the rim..
In the UK the law prevents you from having solid tyres on cars, but your allowed to have them on cycles, and I so hate punctures!
How to avoid wheelspin ? (My last job I spent 2 years driving 3 wheel electric vehicles and a new model one we had suffered from wheelspin so bad it used to chew up the road if you put your foot too far, where as the older designs worked flawlessly, how come the mixmatch ?)
2 wheels at the front, or 2 wheels at the back ?
(Again in my last job, you had to hang out of the cab when you did 40mph around corners so as to balance the vehicle and stop it tipping over, something I'd like to avoid in my own design..)
Aluminum body shell panels surrounding a cork insert for passenger protection ?
We have a 60kg weight limit, and our budget is around $2,000 for the initial build, so no fancy expensive solutions!
I'm looking at an all bolted design rather than welded for ease of maintence, easy design changing and it saves me learning to weld, buy equipment too. (We have space issues with tools/etc. being that we live in a 116 square foot room, so lack of space for say our own lathe..)
Centre of gravity issues, being that we have tall (100mm at least.) and wide speed bumps here, I don't want it catching on them like so many other vehicles do here, so wonder how you go about making sure the thing stays upright due to its 3 wheel design.
I'm guessing making sure you have lots of distance between the wheels yes ?
But then we want it not too big so we can park easily and get in and out of traffic, though I realise that a 2 seater side by side design (So you can chat to the other person and they can spot traffic issues for you..) will be getting on for the width of a car, I'm unsure length wise, but it would be nice not to have the same issues as parking an estate/station wagon car!
Any other design thoughts people have would be interesting to hear.
I worry about such things as wheel collaspse. (I've previously dabbled with designs way back when I was younger and noticed you could carry half a ton of firewood on pram wheel go-cart, but take those corners slowly!) so I'm not sure whether to go for spoked wheels or something stronger. Whether to use cycle parts all the way, or maybe go-cart parts here and there for strength.
Thoughts welcomed/etc.
Electric vehicle design questions
I suggest MOSFET choppers to control motor speed. Simple optical encoders on the wheels to prevent spinning.
A cheap microprocessor to control it all (probably under $5 US). Figure 3 to 6 A/D channels depending on what you want to watch. Battery voltage, current, charge rate, etc. Chop rate above 20 KHz for the motor to prevent motor whine. Around 1 KHz if you want the microprocessor to handle it unless the micro has a built in PWM.
Lead acid batteries are the most forgiving for your initial trials. Move up to Li Ion as you get more experience. You will want a charge control chip matched to your Li Ion chemistry.
Passenger protection: A flashing light on the top. A sound generator to warn pedestrians. (see previous thread) Aluminum and cork are a waste. Canvas/nylon for weather protection.
Bicycle tires initially for cost reasons. Work out the tire issues once you get an operational vehicle. Get balloon tires like those found on old American Schwinns. Or Tour de France type tires. Changing them every 200 miles or so should be acceptable for experiments.
Keep the weight down. Allow for additional battery packs for longer trips.
Seats: cut up cheap lawn chairs?
At 60 Kg your best protection is visibility. Lots of LEDs.
You are going to build 2 to 5 vehicles before you get it right. Plan to throw the first one of everything you do away. That includes hardware and software.
A cheap microprocessor to control it all (probably under $5 US). Figure 3 to 6 A/D channels depending on what you want to watch. Battery voltage, current, charge rate, etc. Chop rate above 20 KHz for the motor to prevent motor whine. Around 1 KHz if you want the microprocessor to handle it unless the micro has a built in PWM.
Lead acid batteries are the most forgiving for your initial trials. Move up to Li Ion as you get more experience. You will want a charge control chip matched to your Li Ion chemistry.
Passenger protection: A flashing light on the top. A sound generator to warn pedestrians. (see previous thread) Aluminum and cork are a waste. Canvas/nylon for weather protection.
Bicycle tires initially for cost reasons. Work out the tire issues once you get an operational vehicle. Get balloon tires like those found on old American Schwinns. Or Tour de France type tires. Changing them every 200 miles or so should be acceptable for experiments.
Keep the weight down. Allow for additional battery packs for longer trips.
Seats: cut up cheap lawn chairs?
At 60 Kg your best protection is visibility. Lots of LEDs.
You are going to build 2 to 5 vehicles before you get it right. Plan to throw the first one of everything you do away. That includes hardware and software.
Engineering is the art of making what you want from what you can get at a profit.
> Canvas/nylon
Not suitable in this location due to vandalism issues.
> A flashing light on the top
Not legal on UK cycles.
Otherwise, the other suggestions I'd agree with.
I'm not sure which size wheels to be looking at, will cycle wheels be able to handle the sideways force and not collaspe doing corning when the vehicle is loaded with 2 people ?
Not suitable in this location due to vandalism issues.
> A flashing light on the top
Not legal on UK cycles.
Otherwise, the other suggestions I'd agree with.
I'm not sure which size wheels to be looking at, will cycle wheels be able to handle the sideways force and not collaspe doing corning when the vehicle is loaded with 2 people ?
I am keen on aluminum, though I imagine some of frame to start off with will be steel because I've got some of that laying around and its cheaper to make mistakes with.
Less keen on fibreglass, not so easily repaired, burns nicely. (Hence the idea of cork, it tends to smoulder I've heard.), aluminum panels appeals, unpainted (So you can more easily clean the graffitti off and worry less about scratches.) but I imagine the bodywork will come a while after getting the mechanics sorted out.
The thinking behind the alu and cork panels is to try and get something to absorb impacts when a vehicle hits you, or you hit something
bit like how you parcel up stuff with lots of polystyrene chips.
For some reason I'm reminded of I think an Woody Allen film where the car fills with foam upon impact. Safety is important so I want it a Volvo approach, rather than a Fiat Panda design.
At the moment, just trying to figure out which is best place to put the drive wheel, front or rear, bearing in mind it also needs to be pedalled. (Part of the law here, 15mph electric motor speed limit and you have to pedal at the same time, else its going to cost a lot more to do a true electric car.) whether steering should be two front wheels, or as Bucky went, rear wheel. (I've not heard nice things about rear wheel single steering and my efforts to learn to use rear wheel steering trollies hasn't been successful over the years..)
Less keen on fibreglass, not so easily repaired, burns nicely. (Hence the idea of cork, it tends to smoulder I've heard.), aluminum panels appeals, unpainted (So you can more easily clean the graffitti off and worry less about scratches.) but I imagine the bodywork will come a while after getting the mechanics sorted out.
The thinking behind the alu and cork panels is to try and get something to absorb impacts when a vehicle hits you, or you hit something
bit like how you parcel up stuff with lots of polystyrene chips. For some reason I'm reminded of I think an Woody Allen film where the car fills with foam upon impact. Safety is important so I want it a Volvo approach, rather than a Fiat Panda design.
At the moment, just trying to figure out which is best place to put the drive wheel, front or rear, bearing in mind it also needs to be pedalled. (Part of the law here, 15mph electric motor speed limit and you have to pedal at the same time, else its going to cost a lot more to do a true electric car.) whether steering should be two front wheels, or as Bucky went, rear wheel. (I've not heard nice things about rear wheel single steering and my efforts to learn to use rear wheel steering trollies hasn't been successful over the years..)
You may have an issue with weight if you use steel or even aluminum if you use enough of it. What are the requirements you are looking for? Speed of pedaling or by electric motor? distance able to travel on either pedal or motor? that sort of stuff.Nanos wrote:I am keen on aluminum, though I imagine some of frame to start off with will be steel because I've got some of that laying around and its cheaper to make mistakes with.
Less keen on fibreglass, not so easily repaired, burns nicely. (Hence the idea of cork, it tends to smoulder I've heard.), aluminum panels appeals, unpainted (So you can more easily clean the graffitti off and worry less about scratches.) but I imagine the bodywork will come a while after getting the mechanics sorted out.
The thinking behind the alu and cork panels is to try and get something to absorb impacts when a vehicle hits you, or you hit something
For some reason I'm reminded of I think an Woody Allen film where the car fills with foam upon impact. Safety is important so I want it a Volvo approach, rather than a Fiat Panda design.
At the moment, just trying to figure out which is best place to put the drive wheel, front or rear, bearing in mind it also needs to be pedalled. (Part of the law here, 15mph electric motor speed limit and you have to pedal at the same time, else its going to cost a lot more to do a true electric car.) whether steering should be two front wheels, or as Bucky went, rear wheel. (I've not heard nice things about rear wheel single steering and my efforts to learn to use rear wheel steering trollies hasn't been successful over the years..)
Single wheel steering simplifies the mechanics.
Of course if you use independent electric motors on the power wheels they can be used for drive by wire. Which may lead you to pedaling to drive a generator using the electronics to parcel out the energy in turns. That also gives you the option of charging the battery for reserve power while standing still. Such a set up also means no gear changing for human drive.
A look at the BMW Isetta might also be useful.
Of course if you use independent electric motors on the power wheels they can be used for drive by wire. Which may lead you to pedaling to drive a generator using the electronics to parcel out the energy in turns. That also gives you the option of charging the battery for reserve power while standing still. Such a set up also means no gear changing for human drive.
A look at the BMW Isetta might also be useful.
Last edited by MSimon on Tue Aug 19, 2008 5:06 pm, edited 1 time in total.
Engineering is the art of making what you want from what you can get at a profit.
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esotERIC D
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I'm thinking that with the constraints you are working wiht somehthing like these (plus one or two electric hub motors) are in your ballpark.
http://www.velomobiling.com/MoreThanOne
perhaps you can find inspiration here
http://www.3wheelers.com/enter.html
and this looks cool, ya know, later on
http://www.rqriley.com/xr3.htm
But I have to say that if you want saftey out of a 60kg, $2000, three wheel electric bicycle your best bet would to wear a helmet.
http://www.velomobiling.com/MoreThanOne
perhaps you can find inspiration here
http://www.3wheelers.com/enter.html
and this looks cool, ya know, later on
http://www.rqriley.com/xr3.htm
But I have to say that if you want saftey out of a 60kg, $2000, three wheel electric bicycle your best bet would to wear a helmet.
Mmm... requirements;
Stability when turning, eg. no easy flip over.
Most things are up in the air and not decided upon, apart from the legal UK requirements which restrict one to certain things here or there.
Electric motor speed is limited to max 15mph whilst also pedaling (Production vehicles once they have done trials/tests are allowed to be used on just electric without the need to pedal, but homebuilt requires one to pedal when using electric.) which isn't so much of an issue with average London traffic now at some 9mph
But it would be nice to be able to pedal at a high speed for long journies and when using main A roads with dual carriage ways when you need plenty of speed to keep up with traffic.
Stability when turning, eg. no easy flip over.
Most things are up in the air and not decided upon, apart from the legal UK requirements which restrict one to certain things here or there.
Electric motor speed is limited to max 15mph whilst also pedaling (Production vehicles once they have done trials/tests are allowed to be used on just electric without the need to pedal, but homebuilt requires one to pedal when using electric.) which isn't so much of an issue with average London traffic now at some 9mph
But it would be nice to be able to pedal at a high speed for long journies and when using main A roads with dual carriage ways when you need plenty of speed to keep up with traffic.
If you use electric motors for your transmission both passengers could pedal. At a speed each was comfortable with. Chopper supplies could match the different pedaling speeds. That allows both passengers to contribute what they can.
If you are moving at 9 mph you can pedal faster to save up energy for speed bursts. That implies a hand throttle on your steering gear.
If you are moving at 9 mph you can pedal faster to save up energy for speed bursts. That implies a hand throttle on your steering gear.
Engineering is the art of making what you want from what you can get at a profit.
I bicycle, and my favorite bike is an old fat-tire Schwinn. It presently sports a fairly expensive set of Bontrager tires featuring Kevlar belts for puncture resistance.
Wear will be greatly affected by compound. Bicycle tires are typically not intended for especially high mileage, and they anticipate low rear wheel power and modest speeds. I suspect the tire industry could make similar tires which are more durable, optimized for lightweight electric vehicles.
Racing wheel chairs angle the main wheels in. I don't know how much that is for cornering and how much for ergonomics. I think that probably adds some drag and may increase wear, but it might be possible to make the wheels tilt during turns (similar to banking a bicycle) in order to simulate that "leaning to the inside" effect.
Wear will be greatly affected by compound. Bicycle tires are typically not intended for especially high mileage, and they anticipate low rear wheel power and modest speeds. I suspect the tire industry could make similar tires which are more durable, optimized for lightweight electric vehicles.
Racing wheel chairs angle the main wheels in. I don't know how much that is for cornering and how much for ergonomics. I think that probably adds some drag and may increase wear, but it might be possible to make the wheels tilt during turns (similar to banking a bicycle) in order to simulate that "leaning to the inside" effect.
I've done some dabbling in bicycle design.
I like steel for the frame. Aluminum or high tech materials won't save you a gram unless used right, including heat treatment for metals. If you really want to try high tech materials, get the geometry right first in steel. I've concluded that frame design has more to do with weight than material used.
As far as drive, peddle drive train to one wheel and electric drive to another wheel may work surprisingly well. One project I helped on was a trike originally designed for 2 driven rear wheels. After some binding problems the chain to one side was removed. No drive unbalance was noticed.
Rear drive would be preferred, all else equal, as there's more weight for traction on the rear when you really need it. Front brakes work harder for the same reason. Depending on the seating and steering arrangement, front peddle drive may be more convenient.
Much of my recent design work involves a 2 wheel rear trike steered by a aft pivot, tilting the seat into turns. I've also looked into back to back tandom seating.
I like steel for the frame. Aluminum or high tech materials won't save you a gram unless used right, including heat treatment for metals. If you really want to try high tech materials, get the geometry right first in steel. I've concluded that frame design has more to do with weight than material used.
As far as drive, peddle drive train to one wheel and electric drive to another wheel may work surprisingly well. One project I helped on was a trike originally designed for 2 driven rear wheels. After some binding problems the chain to one side was removed. No drive unbalance was noticed.
Rear drive would be preferred, all else equal, as there's more weight for traction on the rear when you really need it. Front brakes work harder for the same reason. Depending on the seating and steering arrangement, front peddle drive may be more convenient.
Much of my recent design work involves a 2 wheel rear trike steered by a aft pivot, tilting the seat into turns. I've also looked into back to back tandom seating.