My new 31 year old "e-bike" !

[morphix]

the C5 is such a poorly designed trike, the rear axle does not have a differential, the steering is difficult to control. It does not matter whether it can be retrofitted with a front or rear kit, the thought of a fast and strong motor on it fills me with fear.

Similar thoughts are now crossing my mind.

How about this.... strip down the C5, discard everything except the body shell, and fit this under it (£280 from Germany on eBay + £8 delivery). Lose the mudguards and weird steering bars of course.

All it needs is 16" wheels at the back, and look this chassis is ideal for 3 hub motors. That seat looks far more comfortable. It go where Sinclair should have put a proper seat on the C5, the penny pincher. Let's bolt it this one on.

 

[morphix]

Is this legal? E-bike law says an e-bike has to have working pedals...how about replacing the C5's big oversized pedals with neat little small folding ones that fold away allowing more leg room for those taller people? The only time those will be unfolded and used is when the battery is totally flat and there's no charge points nearby.

 

[morphix]

could you not make a bracket at the rear to use a hub motor like the above bike?

should then be easy to get the axle sprocket in line stop it going side ways.

4,000W love it! Everything is done LARGE in USA. Supersize my C5!

 

[D8ve]

To keep it legal it's one motor.
And the under seat steering is classic for a recumbent.
The whole recumbent scene is about comfort and efficiency ( well speed is efficient ). As an idea velomobiles are popular but very expensive now. It's the it costs more than a car problem. A cheap velo the aldweigler is circa £3K unpowered. And that's the diy kit!

 

[tillson]

Hi,

Just had a quick read through this thread. My initial thoughts are the weight distribution is wrong for a front hub motor to work. The majority of the weight is over the rear wheels, so I think you will struggle for traction if driving the front wheel, especially going up hill on a wet day.

In order of preference, I think it is best to preserve it for what it is, a C5 and a piece of history, so do nothing except clean, restore and return it to working condition. Maybe consider lighter Li-ion batteries as long as no chopping and carving is required to fit them. This could be fun and rewarding.

If you must do something to it in the way of modification, be subtle and preserve the exterior appeal, forgetting about adding knobs, gadgets, switches, marital aids, lights and digital displays etc. Concentrate on what's under the skin, taking advantage of 30 years of development in drive, brake and energy source technology. But personally, I think you should go for option 1.

Also, bear in mind that this is the fun stage. It's great to plan and dream and imagine whilst high on a bucket load of enthusiasm. Once you get into the modifying, if that's what you choose to do, you will meet problem after problem and unexpected expense, all of which sap enthusiasm. That's when the bodgeing starts and all too often the project either ends up abandoned or turns out to be a gaffer tape abortion. That would be sad because an original C5 would be lost.

I'm not saying that (2) applies to you, but bear it in mind, statistically this is the most likely outcome and it would be a shame to consign a well preserved piece of history to the dustbin.

Good luck, whatever you decide to do.

 

[trex]

you would need to add something like this to the C5 to make it safe first:

 

[Deleted member 4366]

Trex, he's already said that axle mods are beyond his capability, which is a shame because it wipes out so many exciting possibilities. You're right that a diff will make a big difference to control on corners.

Morphix, I'm not sure you got my point about the voltage, so I'll try and make it clearer. You can use voltage to get exactly the speed you want from the motor. A 328 rpm Q85 maxes out at about 15mph in a 16" wheel and produces reasonable torque up to about 12mph. That would be a bit slow in a 12" wheel, where it would produce good torque up to 8 mph and max out at about 11mph. Increasing the voltage increases the speed in direct proportion, so if you ran a 36v one at 48v, the torque would last to 12 mph and the speed back to 15 mph again. The actual torque depends on the current, but modern controllers, like the Kunteng sine-wave ones have current control anyway, so you can have whatever torque you want.

If you wanted a realistic speed of more than 12 mph with that same motor, The 24v 328 rpm version at 48v, would produce good torque up to 16 mph.

Motors don't care about voltage. the only thing the voltage does is affect the maximum speed the motor will spin up to. Powerwise and torquewise, a 36v at 20A is the same as a 48v one at 15A. the only things that change are the maximum speed it will spin to, and the point of maximum efficiency goes up with the speed.

The little Q85 motor in a Brompton, even at 36v 15A, makes the front wheel slip a bit on hills in the wet as the torque makes the thin tyres struggle for grip. I think that sort of power and torque would be OK in the C5 with a wider tyre, but I wouldn't like to say how much higher you could go. Relocating the battery to the front and getting rid of the old motor would make a big difference.

 

[morphix]

To keep it legal it's one motor.
And the under seat steering is classic for a recumbent.
The whole recumbent scene is about comfort and efficiency ( well speed is efficient ). As an idea velomobiles are popular but very expensive now. It's the it costs more than a car problem. A cheap velo the aldweigler is circa £3K unpowered. And that's the diy kit!

I'm not intending to ride this thing roads, really the updating was just for a hobby and for the hell of it...so the legal side of it doesn't really factor into it on how I convert this... however I take your point totally, that it would have to be 1 motor and 250W max to be road legal and safe if I was going to ride around on roads on this thing! Absolutely.

 

[morphix]

Trex, he's already said that axle mods are beyond his capability, which is a shame because it wipes out so many exciting possibilities. You're right that a diff will make a big difference to control on corners.

Morphix, I'm not sure you got my point about the voltage, so I'll try and make it clearer. You can use voltage to get exactly the speed you want from the motor. A 328 rpm Q85 maxes out at about 15mph in a 16" wheel and produces reasonable torque up to about 12mph. That would be a bit slow in a 12" wheel, where it would produce good torque up to 8 mph and max out at about 11mph. Increasing the voltage increases the speed in direct proportion, so if you ran a 36v one at 48v, the torque would last to 12 mph and the speed back to 15 mph again. The actual torque depends on the current, but modern controllers, like the Kunteng sine-wave ones have current control anyway, so you can have whatever torque you want.

If you wanted a realistic speed of more than 12 mph with that same motor, The 24v 328 rpm version at 48v, would produce good torque up to 16 mph.

Motors don't care about voltage. the only thing the voltage does is affect the maximum speed the motor will spin up to. Powerwise and torquewise, a 36v at 20A is the same as a 48v one at 15A. the only things that change are the maximum speed it will spin to, and the point of maximum efficiency goes up with the speed.

The little Q85 motor in a Brompton, even at 36v 15A, makes the front wheel slip a bit on hills in the wet as the torque makes the thin tyres struggle for grip. I think that sort of power and torque would be OK in the C5 with a wider tyre, but I wouldn't like to say how much higher you could go. Relocating the battery to the front and getting rid of the old motor would make a big difference.

Thanks d8vh for explaining that so clearly. That certainly helps make things clear on the battery side of things and motor choice.

The original C5 motor is rated:

12V 29A 250W 3300 RPM

 

[trex]

I'm not intending to ride this thing roads, really the updating was just for a hobby and for the hell of it...so the legal side of it doesn't really factor into it on how I convert this... however I take your point totally, that it would have to be 1 motor and 250W max to be road legal and safe if I was going to ride around on roads on this thing! Absolutely.

the C5 can't be used on rough surfaces. The rear brakes are on the right, the motor is on the left.
Unless you fix it properly, it won't be pleasant or safe to ride. BTW, you can't bolt that 400 Euro Triton Pro kit to the C5. It's a toy trike on its own.
I test rode a 20" wheeled trike with rigid rear axle last year. Going round a bend at anything more than 8mph would have tipped the tricycle over. So what's the point of fitting a kit that would propel the C5 faster than 8-10mph?

 

[morphix]

Hi,

Just had a quick read through this thread. My initial thoughts are the weight distribution is wrong for a front hub motor to work. The majority of the weight is over the rear wheels, so I think you will struggle for traction if driving the front wheel, especially going up hill on a wet day.

In order of preference, I think it is best to preserve it for what it is, a C5 and a piece of history, so do nothing except clean, restore and return it to working condition. Maybe consider lighter Li-ion batteries as long as no chopping and carving is required to fit them. This could be fun and rewarding.

If you must do something to it in the way of modification, be subtle and preserve the exterior appeal, forgetting about adding knobs, gadgets, switches, marital aids, lights and digital displays etc. Concentrate on what's under the skin, taking advantage of 30 years of development in drive, brake and energy source technology. But personally, I think you should go for option 1.

Also, bear in mind that this is the fun stage. It's great to plan and dream and imagine whilst high on a bucket load of enthusiasm. Once you get into the modifying, if that's what you choose to do, you will meet problem after problem and unexpected expense, all of which sap enthusiasm. That's when the bodgeing starts and all too often the project either ends up abandoned or turns out to be a gaffer tape abortion. That would be sad because an original C5 would be lost.

I'm not saying that (2) applies to you, but bear it in mind, statistically this is the most likely outcome and it would be a shame to consign a well preserved piece of history to the dustbin.

Good luck, whatever you decide to do.

Great post tillson, very thoughtful. I have been thinking the same!

Whilst initially it's tempting to want to improve the C5 and fill it with modern technology and tons of power as a show-piece or to say "this is the C5 done RIGHT", the C5 is a vintage electric vehicle and landmark in British history...

There's not that many around in full working condition now, so perhaps you're right, this needs to be approached respectfully and sensitively as more of a restoration, with the aim of keeping it looking and functioning as original as possible. Improving performance (both power and pedaling) if possible, but keeping it road legal.

Obviously the electronics are antiquated by todays standards, and so perhaps the controller and POD (the LED's which show motor state and power) could be replaced perhaps with something more modern and functional.

The motor, that's a big question mark....I'm just not sure... perhaps sticking with the original motor (and fitting a second original motor on the other side of the axle might improve the balance and maximise performance). Adding a second original motor opposite side of axle and installing a 24V controller and second 12V 36Ah battery, seems to be a common restoration upgrade approach on the c5alive forum. So at least we know that works well and is easy enough to do. However, that makes the C5 no longer road legal, so that has to be considered.

Really the C5 had costs cut everywhere. It was produced around a very low price-point...ideally, I think the C5 should have had 2 motors in if it was to cope with even inclines over 6% without pedaling or be taken seriously as an electric vehicle..

Obviously fitting 2 motors though takes it out of the e-bike legal limit and puts it into the "AM" moped category..so you'd need vehicle type registration, a driving license with CBT/AM category as a mininium, insurance etc..it starts to get very silly and expensive to ride on the road what is really an e-bike pretending to be a small car at the end of the day! Rather pointless.

So yes, I think you're right, restoration and keeping it all original is probably the most sensible approach (and the voters seem to agree so far!).

I've never ridden a C5 so have no idea how powerful they are or how they compare to e-bikes. I've only watched videos and read reports of them overheating and struggling with even modest inclines which most 250W e-bikes would just fly up. The main problem seems to be the thing is grossly underpowered for the weight. People often say though on videos you watch about the C5, it is quite nippy, the pull and acceleration is quite impressive from a standing start, and being so low and close to the road, you have the impression of it being faster than it really is (12mph).

The original test data for the C5 and motor performance is available online and is interesting to look at, and explains why the C5 frequently suddenly just cuts-out and comes to a standstill so often.

The original C5 prototype was put on the Brookland hill test and they recorded precisely how much incline the C5 can take before the motor needs to be switched before the temperature of the motor reaches a point of overheating and burning up the controllers components, and even melting the wheel rims (when braking).

They determined the cut-off should be at around 6% incline - that's the point at which the C5 motor and controller begins to get very toasty unless you pedal hard. So the C5's controller has 2 safety features engineered in and designed to cut-off power to the motor to. I've seen C5 owners who disabled one or both of these security features, and sure enough..the C5's controller went up in smoke eventually as it couldn't handle the amount of current being drawn by the motor.

That really is the main thing I'd want to focus on in terms of restoring the C5, making it just function well as it originally should have, but closer to a modern e-bike performance, if that is possible given the weight and rear axle assembly challenges.

So here's how I think this restoration (and any upgrade) is best approached...

a) Get the C5 restored and running again completely original, changing nothing except the battery with another lead acid 12V 40Ah one.

b) Assess how well the C5 performs locally in my area under the original spec.

c) If it doesn't perform very well or there's room for greater efficiency and performance, then attempt to upgrade the gearing and/or the motor and controller, so it doesn't automatically cut-out and can cope better with hills, whilst keeping it still looking original and 100% road legal.


Efficiency:

Originally the C5 had a quoted 20 miles range on a full charge. That however is with pedaling on every incline else riding only under power on a nearly flat road!...

The reality of the C5 range and efficiency is this..

The range is around 10 miles before the battery is totally flat, and that falls much lower if you live in an area where there's lots of hills, unless you pedal on every modest incline. Pedaling the C5 is bloody hard work even on modest inclines from what I've seen! People are puffing and breaking out into a sweat after about 500 yards or so.

This seems to be largely down to the poor gearing and the sheer weight of the C5.

So perhaps upgrading could address these two issues:

a) putting in proper gearing for pedaling
b) dramatically reducing the weight by replacing the 15kg lead acid battery and all the original motor and stuff with lighter modern technology.

Moving to a modern e-bike 250W motor and Li-Ion battery could reduce the overall weight by 20-25% I think, and selling all the original parts from the C5 would more than pay for this restoration and the C5 itself!

How well improving the gearing and switching to a modern 250W motor and controller would translate into a more efficient pedaling and e-bike experience I'm not sure.

A good starting point seemed to be the C5alive club website and forum. I've tried to gather opinions and advice from their members forum where there's a lot of enthusiasts who have done all kinds of mods (mostly in the UK but all over the world). There's some talented engineering types there who regularly restore and sell C5's as a business.

I've hit a brick wall though and no responses to my posts. It seems the C5 club is very much a tight clique thing, and they don't take newcomers readily or just don't spend much time on the Internet or forum...so I've just had to read as many threads as possible and soak up as much info as possible about the C5 and how other restorations and modifications have gone.

The impression I'm getting is that the original motor is superior to modern e-bike motors, as it was engineered specifically for the C5 and a light electric vehicle, so actually it's pretty well engineered and the simple gearing arrangement does provide a lot of torque for the motor to maximise that power.

This raises the questions....

Could the original motor be retained, and a better modern controller added which doesn't cut out used to replace the old 1985 controller?

How much improvement in pedaling performance and efficiency would adding some gears provide? Can this be calculated precisely, and what type of gears would be best and/or easiest to fit?

Again, based on my crawling all over the posts on the C5alive forum, on the gearing question it seems that most C5 owners go for the old sturmey archer hub gears. I'm not sure whether is due to practical reasons for easy fitting and the fact they're easy to conceal for owners wanting their C5's to look visually unchanged.

 

[Gubbins]

This is interesting and can't wait to see how it develops..
Good job you have too much time on your hands..

 

[morphix]

Damn. I think I nearly wrote an essay there at 1,000 words! I'm trying to express my thinking though and thoughts out aloud, and bounce ideas here, so sorry if I'm rambling a bit guys!

Maybe someone will pick up on something I've read though and have some good ideas on how to restore or improve the C5.

 

[morphix]

This is interesting and can't wait to see how it develops..
Good job you have too much time on your hands..

It is very interesting Phil and quite a challenge!

The time is going to be a problem as I don't have loads of it to spare, as I work full-time. It will have to be a gradual project done over many weeks. Another problem is the C5 is in my storage unit as I live in a 2nd floor flat and it's just not practical to work on it here. My storage unit is only 10ft x 4ft, so there's not a lot of space to walk around the C5! However I have very good relations with the storage firm and they allow me full use of the factory floor space, so I can easily work on the C5 there.

I'm not very good at mechanical things, although I have managed to convert 3 or 4 bicycles now to electric, so I'm up for the challenge. That's really why I wanted to do this via the forum, and involve you guys as much as possible, to make sure it's done the right and best way.

 

[tillson]

Damn. I think I nearly wrote an essay there at 1,000 words! I'm trying to express my thinking though and thoughts out aloud, and bounce ideas here, so sorry if I'm rambling a bit guys!

Maybe someone will pick up on something I've read though and have some good ideas on how to restore or improve the C5.

It helps to put your thoughts into written words. You can get things in order and see potential issues more clearly v

 

[morphix]

Trex, he's already said that axle mods are beyond his capability,

I can do some mods to the rear axle myself I think. Just nothing major like machine engineering new parts from scratch as I don't have a proper workshop and the equipment, even if I had the know-how or guidance!

If it's deemed worthwhile making new parts and re-engineering the rear axle to improve the gears and motor performance, I suppose I could pay someone to make metal parts like brackets etc if these cannot be readily soured..and if it's not too expensive. I'm sure I could then fit myself from instructions.

I have a fairly tight budget of around £300 to restore and upgrade the C5...I'd like to keep to that budget if possible, maximum overspend £100!! It's already cost me £375 so far (for the C5 itself + delivery + a new 12v battery).

 

[morphix]

It helps to put your thoughts into written words. You can get things in order and see potential issues more clearly v

Amen to that! Certainly helps me..I have to go through this process.

Some people might either follow an existing approach known to work, else just immediately go to work with their own ideas and figure it out by trial and error..

I have a limited budget though. I don't want to get this wrong or do it, and then realise there's a much better way of doing it.

 

[morphix]

the C5 can't be used on rough surfaces. The rear brakes are on the right, the motor is on the left.
Unless you fix it properly, it won't be pleasant or safe to ride. BTW, you can't bolt that 400 Euro Triton Pro kit to the C5. It's a toy trike on its own.
I test rode a 20" wheeled trike with rigid rear axle last year. Going round a bend at anything more than 8mph would have tipped the tricycle over. So what's the point of fitting a kit that would propel the C5 faster than 8-10mph?

I wouldn't be riding the C5 off-road in the sense of "dirt track" off-road, although I have seen the C5 (all original) ride over uneven dirt track and fields even, and it does seem to cope rather well..it's just not very comfortable as with no suspension and a very hard plastic seat, you feel every bump!

The idea of replacing the entire chassis with that kiddy recumbent bicycle was more a joke that a serious consideration! I guess humour doesn't come across too well on forums though.

I don't think it would be practical or worth replacing the chassis with a different recumbent bicycle. It would be too much of a challenge, and too costly..and it's probably easier to deal with the rear axle limitations on the existing chassis and do what d8vh suggested...fit brackets onto the chassis for proper rear drop-outs allowing a rear hub motor, improved gearing and better disc brakes...

 

[morphix]

Hi,

Just had a quick read through this thread. My initial thoughts are the weight distribution is wrong for a front hub motor to work. The majority of the weight is over the rear wheels, so I think you will struggle for traction if driving the front wheel, especially going up hill on a wet day.

In order of preference, I think it is best to preserve it for what it is, a C5 and a piece of history, so do nothing except clean, restore and return it to working condition. Maybe consider lighter Li-ion batteries as long as no chopping and carving is required to fit them. This could be fun and rewarding.

If you must do something to it in the way of modification, be subtle and preserve the exterior appeal, forgetting about adding knobs, gadgets, switches, marital aids, lights and digital displays etc. Concentrate on what's under the skin, taking advantage of 30 years of development in drive, brake and energy source technology. But personally, I think you should go for option 1.

Also, bear in mind that this is the fun stage. It's great to plan and dream and imagine whilst high on a bucket load of enthusiasm. Once you get into the modifying, if that's what you choose to do, you will meet problem after problem and unexpected expense, all of which sap enthusiasm. That's when the bodgeing starts and all too often the project either ends up abandoned or turns out to be a gaffer tape abortion. That would be sad because an original C5 would be lost.

I'm not saying that (2) applies to you, but bear it in mind, statistically this is the most likely outcome and it would be a shame to consign a well preserved piece of history to the dustbin.

Good luck, whatever you decide to do.

I read your post over again, and I think you're spot on and your words of wisdom have "sobered me" up from some crazy ideas I had about upgrading the C5.

When I first began looking at acquiring a C5, my idea was to not just to fit a new front-wheel drive e-bike kit to replace the old motor, but to see the C5 as an opportunity to have a lot of fun with the electronics and technology side of things (i'm a gadget freak and electronics and programming is a hobby).

I made some sketches of how a 21st century C5 might look, focusing on the POD module and the big space below it on the raised black lower half of the body. I thought it might be a good idea to replace the POD LED's panel with either a Raspberry PI and a large 7" touch screen panel, or a cheap tablet fitted into a custom mounted housing on the C5) and pair it up to an old Bluetooth Speedict I have had lying around (the little gadget which sits between the controller and Android to allow a virtual dashboard and loads more control over the controller settings, plus journey logs and battery analysis etc). This would look very impressive, and have offer sat nav and route planning, better battery monitoring etc.

One guy has started making and selling similar panels for the C5 (his are just LCD mono though and show the speed, distance, temperature etc, still pretty impressive though considering he's designed the circuit himself and even vacuum molded housings himself.

Coming back to your post though... what is the point of putting fancy screens and loads of whistles and bells on the C5 though really? Sure, it looks nice and people go "wow" but does it serve any real purpose or improve the performance of the C5? Nope. Probably a waste of money and time which could be better spent focusing on the gears, brakes and more practically useful things. You could just fit a simple tablet or phone holder if you really wanted sat nav.

What you said in your post is really what this comes down to, not over-complicating it. This project has to be clearly viable in terms of cost and time, and worthwhile carrying out. It's important not to get too carried away and to just focus on the main areas you stated first; cleaning, restoring, and bringing the C5 back to life. Doing what's easiest and cheapest first to achieve that and using all the original resources available, it shouldn't be too difficult or challenging, maybe a couple of weekends and it could be done. I think the electrics are all sound..so it just needs a new battery, and the wiring to the battery re-done. At present the C5 has a lockable "battery lid" which sits ontop of the Oldham custom 12V 36Ah lead acid batteries that were specifically made for the C5. It's not difficult to find a similarly sized replacement battery, however the battery lid won't fit, so that will be adapted else replaced, and another approach taken. That's the first hurdle!

The only "major" part of the restoration (at least from my prospective) is dealing with the significant amount of rust on the bottom of the chassis here:

That definitely needs dealing with, else it will get worse over time and weaken the chassis. I haven't had chance to assess the full extent of bad it is, but half the chassis nearly has rust on it. I'm hoping it's not too deep and just superficial. I think this is going to need a complete strip-down to deal with the rust. I won't attempt that though until I've taken delivery of the new 12V battery and tested the electrics.

The chain also looks pretty rusty and finding a chain that long may be challenging. I have a chain-link removal tool so can probably join several chains together and replace that if need be.

You're quite right in realising your own personal limitations before starting a project like this and considering the amount of work and time commitment likely to be involvement before embarking on it.

I definitely need to have a very clear idea of what I'm doing and go slowly if I'm to avoid making a pigs ear of it or my enthusiasm dropping off! That is something I picked up on the C5alive forum. They have produced some howto and general guide threads for newcomers, and they state that whilst cleaning and restoring a C5 and bringing a non-runner back to life is tremendous rewarding, it's also not something to be taken lightly and there can be quite a lot of work involved.

I am fortunate that the C5 is in such good condition (electrically) as replacing all the original electrical parts can get very expensive...and at least I have the option now of just tidying up and fitting a new battery, or stripping down and selling those parts and fitting a new motor.

If I get really stuck with it, I have a brother not far away who is very mechanically gifted and lots of equipment (he is into kit cars!)...and also the manager of the factory where my storage unit is, is a similar type of guy, and has taken great interest in the C5 already! He has a lot of time on his hands at the factory as it's normally very quiet being just a storage factory. It's possible he might even be persuaded to lend a hand on the strip down and re-assembly which will be the most challenging part for me. He has offered to keep the factory open for me longer too which is handy, as he only lives 5 minutes away.

 

[morphix]

Welcome back from the dead Morphix. Are you OK now? I guess you must be.

I know what I'd so with that C5: Make a new nracket that holds the motor. The idea is to make one 135mm wide with dropouts like on a normal bicycle. You need the one on the right side to have the additional hole or hanger for a derailleur. You then fit a normal geared hub-motor and fit a sprocket to the disc brake mount so that the motor works like a motorised jackshaft with gears and freewheel on the right side. That arrangement gives you gears as well as a more powerful free-wheeling motor. You can change the final gear ratio by the size of the sprocket on the disc mount, though a normal 328 rpm motor with a 1:1 final reduction would probably be about right.

After I clean up the C5 and hopefully it comes back to life with a new 12V battery, I'll definitely give seriously consideration to following your approach I think if the C5 turns out to be seriously underpowered or incredibly difficult to pedal on hills.

I'd like to get a clearer idea of what you propose though! I *think* I get what you're suggesting, but I'd need to see a little drawing or something to to be sure. If you don't mind doing that of course!

Looking at the motors available from China, there are so many motors aren't there..and there's no reason why this has to be a hub motor..it could be just a more powerful or similar version of the existing motor which has better internal gearing, faster RPM and more torque, and it could be mounted similarly, and a chain rigged up to it from it to the rear axle? What do you think the pros and cons are of doing that way, as opposed to doing it the hub motor way and trying to make some proper drop-outs on the rear end?

Few questions..

1) Would fitting disc brakes require significant changes to the current rear axle assembly, or is that something could be done without much change? Do you think disc brakes are a better option than the existing unusual rear brakes?

2) The gears part is an area I'm most confused about. Am I correct in thinking unless hub gears are used on the existing axle, significant modification will be needed to the chassis and rear wheel arrangement, basically a form of drop-outs attached to the chassis, allowing a conventional gears cassette and derauiller to be fitted to the wheel opposite the motor (assuming original motor or something similar left turning the axle).

3) How much efficiency performance gain do you think there would be moving from that present motor setup turning the rear axle with the crude plastic gears on C5, compared to a rear wheel hub motor? Would it be a world of difference, modest, or not sure?