NC24 Stripdown

[Neosophist]

All you need to do to get the frame out is remove the end-can, front downpipes.

Put a trolly jack under the engine to support the weight.

Remove all the engine bolts and lower the engine down, then just lift the bike up and over the engine.

You'll need to take the thermostat off and hoses off as well as rads and everything else as they get in the way..

[Spoonman]

Cheers - Have all of the above (excepting the downpipes) off the bike at the moment in any case so that's all good.

Had been figuring on holding the motor in place and just lifting the frame off it. Have a trolley jack there alright but getting it to hold the motor stable on it's own was looking tricky. Ultimately that probably is the easiest way to do things though alright.

Ordered the remaining fork seals this morning, should be reassembling the remaining caliper and forks next week. Will seat the lot into the lower triple ready to go straight back on then after that.

[Neosophist]

It's easy, not going to drop very far either.. if your worried about the trolly jack just use a couple of breeze blocks and a stiff board to support the motor then lift it off the board when the frames out of the way.

there not very heavy motors, you can easily pick one up and walk around with it so moving it off the blocks isn't hard

[Spoonman]

Howdy all,

Sorry this thread's been dormant for so long but there's been a lot of other stuff happening.

In any case, I'll throw up a few pics later and I've some news about the rebuild which I've no doubt some of you will find a tad distastful... to be honest, I wouldn't blame you either - the purist in me is still a little conflicted about it - however I've persuaded myself that it's the right way to go so please don't judge me too harshly.

Word in advance though - I'm presently living about 20km from my workshop so I'm only getting in, on average about 1 night every 2 weeks - so progress is pretty slow. I'll update this thread periodically as I have news to post.

I'll try come up with something to set the tone tonight.

[Spoonman]

Right - so when I last was here, I had the bike down to the engine and frame, the calipers were fully reconditioned (have pics, will put up), as were the forks after I'd had the bushes machined down to the right height. I was just at the point of starting to clean and prep all the brackets etc. for respray, and then I went quiet.

So - since then - I got sick of trying to get paper and wirebrushes into the small corners so I built a very basic sandblasting enclosure (pics to follow) from some old pallet timber and polytunnel covering. I'm pleased to say that it does the job of capturing the blasting media very well. The blasting gun I'm using is a draper unit which simply attaches to a standard airline. I have one of those el-cheapo Aldi compressors (2HP, 25L) which, whilst it's grand for the smaller parts, struggles to keep up with any larger surface area's. It's not the compressor but the volume that's the problem though so I'll likely look to pic up a 50/100L 2.5HP unit at some point.

In any case, the above setup is outstanding for removing old paint and rust and getting bits ready for primer and paint.


Beyond that, I got the engine out and it pretty much sat on the bench, with the frame in the corner of the shed, for about a year until I found the time to get a wee bit done over the summer (not nearly as much as I'd have liked mind).

Now - here's the contentious bit.

In May of this year - I bought an electric car. The Nissan Leaf to be exact - and whilst I'm not going to go discussing this car any farther than that on a bike forum ( ), suffice to say its performance has been simply outstanding.

So much so in fact, that I've decided to design and construct an electric drivetrain for the '24.

Now before I get labelled a complete heathen, there is still enough of a purist in me that one of the principle policies of the design is that I will not alter, in any way shape or form, any of the original components of the bike. In short - everything will be entirely reversible and I will be retaining all the original hardware.

The vital statistics behind the project concept are as follows:
Conventional drivetrain mass including engine(wet), carbs, airbox, rads(wet), tank(half full), exhaust, reg/rec, etc... comes in aroundabout the 85-90kg mark.

All of the above to be replaced by a 6-pole induction motor, motor controller, battery pack, charger, battery management system and associated brackets and wiring.

The battery pack will comprise of 96 A124 LiFePO4 pouch cells in a 32s3p configuration for a nominal voltage of 115V and a max 10 second repeatable current delivery rating of 625A. This pack will weigh 45kg ex brackets & wiring (so about 50kg all told I expect), and will have a total power rating of 5.4kWh which, on conservative estimation (assuming a mean of 50wh per pack on a specified 66Wh) should permit about 80km range driven in a responsible commuter fashion (this figure allows for 7% safety margin at the bottom of the pack and 3% at the top).

The motor will be either the venerable AC15 or AC20 traction motor driven by the Curtis 1238R-7601 controller. This combination comes in at about 25kg.

The BMS is undecided yet, I may simply service the pack manually or go for whichever of the 32 cell options best suits my needs. Bottom balanced packs of this chemistry are well renowned for their stability so I don't anticipate that the BMS will be hugely taxed in any case. I'm allocating 3kg for the instrumentation and wiring regardless.

Finally then comes the charger - I'll most likely build two versions, one 1kW unit which can be mounted in the chassis and will serve as a charger for commuting, the other will likely be a 10kW unit which will be offboard and will permit delivery of a full charge in about 40mins. I would anticipate the use of this unit at track days etc...

The 1kW charger is expected to come in aroundabout the 7-8kg mark although this may be revised upwards to as much as 10kg during the design - it's a little open ended at the moment. In any case it will be a removable unit to facilitate weight reduction when required.

So all told, the EV drivetrain rings in at about 85-90kg and so, will serve as a direct mass replacement in the chassis.


Performance;
The conventional drivetrain is a (spec) ~50hp unit with ~25ft.lbs of torque. Realistically, it's going to be less than this on both counts in the average instance unless the motor has been rigourously maintained.

The replacement drivetrain will develop between 80 and 110 ft.lbs of torque and has a rev range of 0-6500 rpm with torque beginning to drop off dramatically after about 4.5k.

Now, with the above points in mind, we look to the conventional gear ratios and seek to optimise the new drive to match or exceed these ratios. I have all of these numbers on my computer at home so I'll come back to this point later however, as I recall, I concluded that direct driving the rear on a 4:1 reduction gear would provide vastly improved acceleration but would limit top speed to about 84mph, whereas a 3.5:1 ratio would provide comparable accleleration and a top speed of approx 100mph - the latter does present potential current loading concerns though on account of the longer period of heavy accleration presented.

Regardless, 80mph is perfectly appropriate as a roadgoing max speed, and similarly, on a tight circuit it would still provide plenty of grin factor. I'll inevitably refine these numbers through experiment once the drivetrain is operational in any case.


Suspension and handling:
The total mass will remain, to all practical extents, the same as it is on the stock bike, so no additional suspension works will be required over what would be considered in any case.

However - what is worth noting is that the engine is a stressed member of the frame, hence appropriate braceplates will be required in order to maintain the regidity of the frame in the absense of the engine block. These components will require significant consideration.


... I think that covers all of the more obvious technicalities involved - I have quite a few other notes done up but they're all on my home computer. I also have some shots of the progress so far which I'll post up in dribs and drabs as I expect that progress will be rather slow on this project on account of my time contraints and the costs of the various aformentioned components - expect 2-3 year project timelime - but I'll post up what I get done as I get it done.

[Neosophist]

Interesting.

They were 60hp stock, highest one I have had dyno'd at the wheel was 57hp.

Sounds like it will become really torquey.

[Spoonman]

yup - torque at the expense of peak power - the AC20 supposedly has a 45HP equivalent rating (make of that what you will - the whole equivalence thing isn't an exact science). So it'll be an interesting balancing act to get the final stage gearing into that sweet spot where you've enough torque to make it fun to ride, but you're not running the motor too fast at motorway speeds.

Ultimately though, it's the simplest part of the whole project as it can be done by trial and error for the sake of a few different front/rear sprocket combinations.