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Discussion Starter #1
This was a Cagiva 125 that I converted a few years back using lead acid batteries, an original Etek brushed DC motor and an Alltrax 7245 controller.
Those batteries didn't last long as I gave them quite a beating. I've since replaced them with 72 LifeBatt 10 Ah cells, to give a 72V 30Ah pack. The pack is split into two 36V subpacks each with its own 8A charger and Fechter/Goodrum BMS.

I just got the bike back on the road last week and the combination of voltage hike, taller gearing (13:60) and weight loss means it now performs much better. Not sure of the top speed yet as I'm taking things easy with the batt pack for the first few cycles, but she's still pulling strong at 55 mph.

One important lesson I've learned from upgrading this bike is that it takes an inordinate amount of time to build a battery pack and BMS yourself if you use small cells and are electronically disadvantaged like me. I've learned a lot in the process, but if I were doing it again I think I would go with larger format cells and an off-the-shelf BMS.

Now it's done I'm looking forward to making a start on the next project – a dual motored electric mini :)




 

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Discussion Starter #4
Thanks Major! It's not too shabby, but not quite ready to go up against Lightning yet :)

Cheers Ripperton. I plan to do a video some time soon, but we've got an excess of weather right now. I've been watching your progress on your bike too. Very nice fabrication work so far!
 

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Malc, about time you showed up at a TTXGP race innit? It's a long trek down to Brands Hatch for you, but there's lots of cool people to meet and lots of cool bikes to see. We're racing there this weekend if your free..

Great job again on the Cagiva, can't wait to see the Mini!

Steve
 

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Discussion Starter #6
Steve: I'd really like to get down to one of the races and meet up and take a closer look at the race bikes. I can't make it this weekend as I'm going to Ireland, but will definitely try to make it down soon. Do you go to all the TTXGP races?
 

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Aye, I've been to all but the US series to support our 3 TTX02's trackside. This will be the last of this year in the UK, the wold final is at Albicete in Spain end of October. Too far for you?

Steve
 

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Discussion Starter #8
I hadn't realised this was the last race in the UK. I've been watching the videos of the races and get the impression there's a really good atmosphere at the meets. Albicete would be great, but funds are a bit low at the moment so I need to get my head down and do some paying work. Please let me know if you're anywhere near this half of the country in the near future so we can meet up.

Malcolm
 

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Hi MalcolmB,

Nice bike indeed. It really looks clean. I'm looking at converting the same model. Can you tell me more about the aluminum that you used for creating the box? What kind of aluminum is it and what thickness? I'm also interested in finding out the welding machine you used for this. Could I use any TIG welder or does the used material require any special power rating?

Thanks!!

btw, I was at the TTXGP in Assen last weekend. Great show and friendly/open atmosphere! I'm predicting ICE bikes will have a hard time keeping up in 4-5 years time, based on the speed improvements over last year.
 

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Discussion Starter #10
Thanks AT. The battery box and motor housing are both made from 3mm thick aluminium, with 5 or 10mm thick reinforcement at mounting points. I don't remember the exact specification of the sheet I used for the box, but it was from the 5000 series, possibly 5082. The motor housing is made from 6082 channel measuring 100x50mm. The welds were all made with 5356 filler rod, which is a good general purpose filler for 5000 and 6000 series alloys. I used a Murex Tradestig AC220 welder with current in the range 80-95A, but you could use any decent AC TIG welder.

What motor/controller/batteries are you planning to use for your conversion? Any photos?
 

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Discussion Starter #11
Just to add, when you weld aluminium alloys it reduces the strength in the heat affected zone to that of raw aluminium. To regain maximum strength the part has to be heat treated. Unless you have access to suitable equipment this means you have to place welds in areas of low stress or make them oversized.
 

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Thanks for the info. That's very useful to know.

I don't have the bike yet, still in planning stages.

Best option so far seems:
Heinzmann SL-EC 180 Type 22B Brushless motor
Turnigy nano-tech 5000mah 4S 45~90C Lipo Pack

5 batteries in series x 5 batteries parallel = 25 batteries resulting in 99 volt 2,5 kWh. Might start with less parallel to keep the costs down. This would weigh 11,6 KG, measure 19X19X19 cm without casing and wiring.

To compete in TTXGP I would need to double again the battery pack. On paper that should be competitive because the weight of the bike would be much lower than what's currently competing. Reliability of the brush less motor would probably make it already a bit competitive because many teams have problems with the brushes in the Agni motors.

Do you know what the weight was of the ICE engine you took out of the bike?
 

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Discussion Starter #13
Sounds like a very good plan. I hadn't visited the Heinzmann site for a long time. Those water-cooled Perm motors look very promising. Do you have prices and a suitable controller in mind?

Those Turnigy nano-tech are great little packages. If I was starting again I would probably choose them myself, unless I could get hold of some of the large format A123 or Kokam flat cells.

The complete engine with all ancillaries, except the exhaust, weighed just under 30 kg if I remember right.
 

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I've taken the jump and bought a Cagiva donor bike and an AC Welding machine. So now I can't go back anymore. See a pic of the Cagiva Mito attached. The fairings are missing on this pic, but I do have them although they are in a bit of a bad shape.

Because of budget limitations I've reconsidered the electric motor to use for the project. If the project is succesfull I'll consider using a Perm water cooled motor. But for now I've chosen the Golden Motor BLDC HPM5000B. This motor comes with a controller HPC500A. Pics attached.

For the batteries I've chosen the
Turnigy Lipoly batteries from HobbyKing. My plan is to first buy the minimum amount to test the setup. With minimum I mean enough volts and Amps, but little kWh's. I haven't decided on a charger and/or BMS yet. I find it hard to make sense of all the options out there.

Meanwhile I've been trying to design with Sketchup a "sub frame" for the Cagiva that will hold all the components. I want to have enough space around the motor to have the option to add water cooling. Don't know if that's realistic at all, but it would be interesting to see if some more kW's can be squeezed from the GM motor as that would make it a great value motor.

I'd be interested to learn what you all think about this plan. Any obvious flaws? Suggestions?

I'll see if I can post some screenshots of the design thusfar.

Cheers,
Alex


 

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Discussion Starter #16
Hi Alex. Good to see you've made a start. I've looked at that motor a couple of times myself. I'll be interested to hear how it performs.

Your drawings look good. Just a couple of things caught my eye:

It looks as if the only thing preventing the lower battery cage from swinging freely is a thin strap that ties it to the motor mounting. If that's the case you might want to stiffen that link up a bit to reduce any flexing.

It's hard to be sure from looking at the drawing, but it looks as if the motor may be a bit high. On my bike the centre of the motor shaft is only one centimetre higher than the centre of the swingarm pivot. Remember that the suspension will sag when bike is loaded up.
 

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Discussion Starter #18
The swingarm is a lightweight alloy casting. There's no easy way to suspend the motor from it and I personally wouldn't try it. It would need strengthening to support the additional stresses imposed by the motor. This would be a much easier proposition with a steel swingarm.

I don't have any problem with anyone else posting anything here as long as it's remotely relevant.
 

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@ MalcolmB
You're right about the hight of the motor. I've yet to measure the height of the axis in the ICE. I'm thinking it should be the original height unless the needed gear ratio requires much larger or much smaller gears. Did you use the original height? When you say 1cm higher, do you mean when the bike is straight on it's wheels, with weight of the engine/motor but without a driver? In the drawing it's 5cm higher, so much to high.

Thank for the tip on the battery mounting. Will need to rethink that anyway when the motor is lowered..

About the motor; I've noticed that Mars Electric now has the ME0913 on their site and it seems to be in stock. This motor is used by RIPPERTON and has similar kW/$ (0,018 kW/$) ratio as the Golden Motor, but much more power 12kW vs 7kW. To my knowledge this kW/$ ratio is the best available. The ME0913 will fit, so I'll have to choose between them. Choices, choices. However I'm designing the bike to be easy and affordable for anyone to copy. Probably when also calculating the cost of the controller I'll probably want to stick with the Golden Motor..

@RIPPERTON
Will create a thread once the build starts and I have something substantial to post. Thanks for the tip.

I do see the benefits that mounting the motor to the swing arm would have. However I'm trying to make this build as easy as possible to be reproduced by anyone that wants to. That basically rules out any welding to the original frame. Requiring welding equipement and experience would reduce the potential audience considerably. Not to mention that most people aren't comforable making irreversable changes to an expensive part such as the frame. Not to mention I haven't welded anything ever before, so I don't trust myself welding anything to the frame.;-)
 

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Discussion Starter #20
If you keep the motor height close to the original height of the front sprocket you should be fine. I measured my motor to be 1 cm higher than the swingarm pivot on level ground, without batteries or rider.

Designing your motor and battery mounts to be easily copied by others is a great idea. I also designed my motor subframe so that it would take any of the commonly available pancake motors. I think most of the Mars motors would fit as well.

Mounting the motor on the swingarm solves a couple of problems at once, i.e. eliminating chain/belt stretch and providing more space for your battery pack. One idea I'd like to try would be to fabricate a swingarm with the motor mounted concentric with the swing arm pivot, so the pivot runs through the hollow motor shaft. You could this with an EnerTrac hub motor.
 
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