I hope your battery pack doesn't get smashed on curbes and rocks down there. Just my 2 cents, but I'd put it on top of the frame so it's more protected. You have that space right in front of the seat that would work great for your pack.
A few things...
This list keeps getting longer and longer! It was originally just 2 things and now it's 6.
1. You NEED torque arms on your hub motor. The drop-outs will spread and bend from the motor torque being applied to them. While I know you don't have 20kw at your motor shaft flats into 1/4" thick solid steel, what you see below will still happen to you. Your drops outs are made from thin wall steel pipe. They were never intended to do more than hold a free spinning wheel axle. The motor torque applied to the shaft flats will spread and destroy those flimsy drop outs like they were aluminum foil! You might get away with 500 watts on them as is and that is a strong maybe. I have an A2B bike that had a 500w hub motor. The beefiness of drop outs are very similar to yours and this was the single largest failure point on these bikes. IF you were going with a mid-drive, your drops outs and swings arms would not be a problem.
2. The swing arms are quite small and light weight. They offer very little stiffness and rigidity. You may find that they bend with the motor torque applied to them. They may be flat now, but give it some time and I bet they start bending. Since you need to drastically improve your drop outs, you might as well make new swing arms or at least reinforce these ones. I'd at least cut off your drop outs and then weld a 1/4" thick by 1" tall rib the full length of your swing arms. In the end of each rib include new drop outs.
3. 12v LED lights are great. However, use your main battery pack and a DC-DC converter to get 12v. You are charging one battery that way. I bet you never even notice the range loss from running lights from your main pack. DC-DC's are pretty cheap. You'll find whatever you need on ebay for less than $25. A DC-DC will always make 12v regardless of your main battery pack voltage. A small 12 volt battery is always dropping in voltage. As it runs out of charge your lights get dimmer and dimmer. If you look at any commercially made EV's, they all implement a DC-DC for the 12v system.
4. 80% of braking power comes from the front wheel. You'll lock up your back wheel and your front brake will be doing hardly anything. The factory front brake will be squeezed as hard as possible and maybe delivering half the braking power you need in front. Drum brakes are the worst! They have no way to get rid of braking heat so they heat soak rapidly. The brake drum diameter is very small so braking leverage is low. As a result you apply them much harder than you do a disk brake and then they just heat soak and fade almost instantly. You already restrung the back wheel. Restring the front wheel with a wheel hub that will take a disk brake. Then install a 203mm rotor on it. Now that you have disk brakes front and rear, get hydraulic brakes. I have several sets of the cheapest Shimano hydraulic brakes and I swear by them! $70 on Amazon for a set is stupid cheap and they work VERY well. I'll never have mechanical brakes on anything I build ever again!
5. Since you should put your battery above the frame instead of under it where it will possibly suffer bashing and damage, now you have room for a mid-drive solution mounted where the engine used to be. This will eliminate that heavy hub motor in the back wheel and all the rideability issues this creates. Outrunners will give you the most bang for the buck and do it at much less size and weight of any other motor option. Yes it means you will need a chain drive again, but this is a small price to pay for the gains you get in every other way from a mid-drive. One biggie is you no longer need to reinforce your swing arms and drop outs (number 1 and number 2).
6. Your scooter was built for maybe 30 miles an hour. With 3kw of motor power, you'll achieve 50 mph and possibly more. The scooter will weigh more than it did with a gas engine. Your ability to brake at the limits of tire grip for many seconds has suddenly become very important! If you look at any of my EV builds you will see that I always improve braking as much as possible.
Thanks for responding to my moped build post, you've definitely given me a few things to think about!
I do appreciate your advice based on the your experience, but I hope you can see a few positive points in my project too.
I'll take your points in order:-
1. Drop out torque. I had read about this problem. Lots of torque on drop-outs never designed to take it.
I might take your advice and fit a torque arm, but for now I have opened out the drop-out and used a stainless steel plate between the axle flat and the swing arm- just visible in 6th and 7th pics above.
2. Swing arm stiffness, I'll see how it works out, if it's an obvious problem, I'll have to modify it as you suggest.
3. I spoke to an electrician friend and he made the same suggestion, electrics are not my strong point, so I didn't think of the DC-DC converter, obviously a better solution than my rechargeable battery. Thanks.
4. Obviously a disc brake on the front would give me better stopping power. I could build a wheel with a disc brake compatible hub, but I'm not sure how I'd mount the calliper. I want to preserve some of the retro look of the bike, and the forks and front hub are part of that. But if I find the brakes are hopelessly inadequate I'll have to carry out further mods.
5. The battery will be housed in a steel cradle under the frame. I don't plan on riding off road so I hope to keep contact with rocks to a minimum! It will have more ground clearance than it had with its two stroke gas motor. I also want to keep the centre of gravity low for easier handling and manoeuvring.
You're probably right about a mid drive motor, but I'm too far in with this project now to make fundamental changes to the lay out. That will have to wait for the Mark II.
When I bought the motor I told the guy I bought it from what sort of performance I was after (30-35mph) and he suggested this set up. But it does seem I might be looking a fair bit more. I'll take it easy on the first test rides a see how it feels!
I'm hoping the weight won't be a huge amount more than the original bike. The battery should weigh about a kilo more than the original engine. I have removed a lot of original components, it had two chains, a centrifugal clutch, pedals etc. It would also hold maybe 5 litres of petrol (gas) that'll be another 4 kilos. It was also designed to carry a passenger, so even with the average 1960's spouse in mind that's got to be 50kgs of weight I won't be carrying.
Anyway, thanks for your advice. I'll keep you posted on progress.
I like retro builds like this. Most of them end up working just fine after the various engineering details, weaknesses and issues get worked out. My builds are no different. I want them to look like the factory product as much as possible. I may think they are done and then I go for a test ride and soon realize I have things yet to work out. Your scooter project will go through this too and probably less of the factory "look" will survive.
I apologize if I sounded critical of your build or like I was presenting that it is a waste if time. That is far from the case! I looked over what you had, saw certain things I've run into myself and told you about them in context of your build. I really hope you get this scooter going and it is reliable and fun as hell to ride! My desire is to help and to not be a hindrance or a critical troll of other peoples projects.
One of those things I discovered after I thought I was done is braking. I was coming down a hill and doing 60mph...not too fast. The light at the bottom turned yellow at that spot where you are either going to run the red light or brake very hard to stop in time. Of course traffic poured into the intersection so stopping was the only option! I applied the brakes and regen and slowing down was just too slow. I was well into the intersection with people honking and swerving around me before I got stopped. That was the last time I had the factory front brake! It nearly killed me! Now I can stop from 60 in much less distance and at the edge of tire grip if needed. You'll find stuff like this soon enough once you get to the point of riding your EV the first few times.
Good luck and good fortune to you! I look forward to seeing your build progress!
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