MAC beach cruiser, through the eyes of a n00b

[Spicerack]

Yes, very nice build there and as mentioned, great atmosphere shots too. I was actually having a look at a cheapo cruiser at a shop the other day- looked really cool even if it was a Huffy! Only $188. Hmm, that plus a Mac would be a nice little cruiser bike to go round the river here in Perth.

What speed do you get out of the 12t with this bike?

Oh, and please please shape that battery box a bit to fit the frame! It would look soooooo much better!

 

[nonlineartom]

I agree it would look better shaped, but it would take a LOT longer to make with my limited tools, perhaps in summer. I'm using the 10T motor and full speed is 25mph on 12S of lipo (when at around 47 volts) I usually run it on the middle speed on the 3 speed switch though where the top speed is about 18-20mph. It's much safer at those speeds considering it doesn't have suspension or disc breaks.

I think this bikes main redeeming feature though is it's weight, it's an alloy frame and because it has no fancy suspension or anything it's as light as a road bike, the mac motor is hardly heavy and I only carry 4 packs of 6s 5ah in the frame which is only about 3KG, the whole setup can be picked up one handed but can still maintain a steady 2kw output on long hill climbs

 

[nonlineartom]

Well I managed to break the motor. I know the 12fet 45A controller is too much for the mac which is why I had the CA limiting the power to 1300W maximum on 12S to stop things melting. Turns out melting wasn't the issue

After setting off on flat ground at full throttle I heard a really loud CLUNK and now the motor refuses to freewheel so it looks like I've seized the one way bearing. I guess it's not designed to handle those kind of loads, the 10T motor does really launch off the line with a lot of force so I guess it was just too much for the bearing to handle.

Good news is cell_man has proved to be an absolute dude once more and has agreed to replace it for free if I play shipping on this occasion reminding me that the motor wasn't designed for that kind of power.

For reference the motor has probably close to 1000 miles of flawless running on it now and this is the first thing to go.

 

[newb]

Good news is cell_man has proved to be an absolute dude once more and has agreed to replace it for free if I play shipping on this occasion reminding me that the motor wasn't designed for that kind of power.

very cool, and paul continues to prove why he's a preferred ES vendor.

in the interim you could try tapping the clutch lightly w/ a hammer, it may free up. but, being that you heard that "loud CLUNK" this may not work. i had one lock up on my wife's bike (bafang style motor) about a year ago for whatever reason and by doing this i was able to get it freed up. then worked in some white lithium grease and haven't had a problem since.

 

[nonlineartom]

It freed up again doing about 40mph down a steep hill (gravity powered only) I hit a small bump and it started freewheeling again. Sure it will go again though soon.

I could really use that throttle ramp up chip that sort of doesn't exist. Something that inhibits the throttle signal so instead of going from 0% to 100% instantly causing a huge amp spike and thrashing the clutch, something that would ramp the throttle signal over 1 or 2 seconds. It would stop the bike from lurching and stop massive amp spikes without affecting the bikes ability to climb hills. Lyen offered a solution but it included ramp down as well which isn't safe enough, If I say no more power, I want no more power.

 

[newb]

good for you and since its working again certainly couldn't hurt to force some grease into the clutch, though its a bit of a pain. even a couple drop of mineral oil is better than nothing.

what about adding a 3 spd switch until to find an answer that doesn't require your involvement? also, wouldn't the break cutoff switch effectively eliminate the ramp down?

 

[nonlineartom]

I use a 3 speed switch, it helps a little but you still get that initial lurch, the 3 speed switch changes the top speed but not the acceleration. Brake cut off would over ride the ramp down on the throttle but my brake cut off lever broke so I'm not using one at the moment. Plus it still is pretty dangerous to have power at all when you let go of the throttle.

 

[newb]

i was thinking if you had position 1 set to something like 30% but you're absolutely right you are still getting that initial lurch. but i might be able to help with the other problem. i received couple extra brake lever sets from Mark H when i bought all those motors, 1's yours if you pay the shipping. probably cost you something like $10 for priority if i can send them as a letter.

 

[nonlineartom]

 

[French]

Very interesting. My wife's MAC freewheels just fine, but it is binding a little bit to where if you let off the throttle, there is a fairly loud winding noise and it slows down fairly rapidly. It doesn't seem to be affecting mileage very much, and sometimes it will actually go away and work just fine. I need to open it up again and inspect a little more.

We have the 8T motors and I'd really like the 10T motors for the hills and off-the-line torque (I really don't need to be going 31mph on a bike, too). However, I am concerned about exactly your issue, and that is durability of the clutch after many hard launches (although, I usually pedal a little bit off the line, and then hit the throttle). Maybe just get in the habit of switching to speed setting 1 for launches? You may want to consider re-programming your controller to reduces the speed settings. Default is 50% / 75% / 100%. Maybe do something like 30-40% for Speed 1? Just an idea as that will definitely add some life to the motor.

Edit: Just realized that newb already suggested the 30% idea. I have mine currently set to 42% / 61% / 100%, and Speed 1 definitely launches softer. I'm sure 30% would be very mild.

 

[nonlineartom]

The 3 speed doesn't change the initial amp spike and therefor load on the clutch and gears. It does change the throttle resolution so x amount of degrees rotation equals a overall lower speed but still. I've got a few 8T motors but I have yet to try them out, got a 6T as well. I do think the 10T is a perfect motor though, as you say you don't want to be going 30mph on an bicycle really, there isn't a bit of road big enough for me to get up to that speed anyway on my commute, better to put that power into torque rather than top speed.