that may not be the best comparison since most folks would choose a higher KV motor than the 5305 to run at such a low voltage, such as a 5302 or 5303. 5305 is wound for high voltages, such as 72 volts, so performance at low voltage is not so good @36v. A 5305 on 36v is like having a V-8 that runs on 4 cylinders.Russell wrote:Then compare the dual eZee's to a single X5305 at 36V/40A/26" which produces 52.5 lbs of thrust at 0mph and just 18 lbs at 15mph.
That's another thing I was thinking that 2 wheel drive might provide but didn't include in my reply as I haven't seen any real world head to head tests to confirm it. Will they really give more thrust at a given wattage? Will they be more efficient with less load on each motor? Less heat buildup?The simulator at ebikes.ca doesn't have any geared motors smaller than an eZee but I still find it useful to use the eZee as a stand-in for one of my 250W motors keeping in mind that I need to adjust the results down by perhaps 20%. Anyway if you pit two eZee geared motors running at 20A against any other single motor running at 40A the dual motors comes out on top by a good margin. For example dual eZee's at 36V/20A/26" will produce a combined thrust at 0mph of 90 pounds and at 15mph it's 36 pounds. Compare that against the BMC V2-T at 36V/40A/26" which generates 78 lbs of thrust at 0mph and 24 lbs at 15mph. Top speed of both set-ups would be 21-22 mph. Then compare the dual eZee's to a single X5305 at 36V/40A/26" which produces 52.5 lbs of thrust at 0mph and just 18 lbs at 15mph. Of course dual Cute's or Bafangs won't be quite as strong as the dual eZee's but you can pick up two of Cutes or Bafangs for less than the price of a single eZee motor.
I'm really looking forward to that part. Being able to power through a corner and maybe doing some controlled skiddingdogman wrote:I really really like front hubs on the street though, since you can power through a corner with both wheels grabbing traction. My town has just about all the wheelchair ramps done on the sidewalks, so I don't need to pop over curbs any.
I chose the X5305 to make the comparison as even as possible selecting motors that had top speeds in the same range, 21-22 for the eZee and BMC V2-T and about 19 mph for the X5303. The next step up, the X5304, might have been a better choice with a top speed of about 23mph at 36V/40A/26". The X5304 would generate lower torque at 0mph (51 lbs) than the X5305 but more at 15mph (29 lbs) but again these would be less than the dual eZee's at 36V/20A/26" at 90 lbs and 36lbs respectively. The comparison was an exercise showing the low speed thrust which can be achieved using two smaller geared motors compared to a single motor while keeping the voltage and total current the same, I was not suggesting someone would necessarily want to build an X5/36V system.will_newton wrote:that may not be the best comparison since most folks would choose a higher KV motor than the 5305 to run at such a low voltage, such as a 5302 or 5303. 5305 is wound for high voltages, such as 72 volts, so performance at low voltage is not so good @36v. A 5305 on 36v is like having a V-8 that runs on 4 cylinders.Russell wrote:Then compare the dual eZee's to a single X5305 at 36V/40A/26" which produces 52.5 lbs of thrust at 0mph and just 18 lbs at 15mph.
...but I get your point.
Yikes. I hope my frame holds up better. I have just under 1,800 miles on it and no cracking yet. Thanks for the heads up on this problem.Qwiksand wrote:I hope you have better luck with your frame than I did, they're notorious for this:
Documented here: https://endless-sphere.com/forums/viewto ... =6&t=14788
Looking at it again it does appear that it cracked where the bottom of the seatpost would be. If the shock had done it I would think the crack would be on the other side of the down tube.dogman wrote:longer seatpost would tend to reinforce that area. It looks to me like where the seatpost ends inside the tube. If further down, a second, cut off section of seatpost could reinforce the area from inside some.
I think you're on the mark here, TD. The crack is at a high-stress point just below the seat tube shock mount, a good 12" below where the seatpost ends.TylerDurden wrote:On retrospect, an internal post may not resolve the cracking. That is not a torque fracture. It appears to be pulling the bracket right out of the tube.
Is it possible that the rear suspension also bottomed out at some point causing a huge spike in the pressure on that area? Or did the higher air pressure you put in the shock prevent that?Qwiksand wrote:I think you're on the mark here, TD. The crack is at a high-stress point just below the seat tube shock mount, a good 12" below where the seatpost ends.TylerDurden wrote:On retrospect, an internal post may not resolve the cracking. That is not a torque fracture. It appears to be pulling the bracket right out of the tube.
It seems that most of these failures happen on large (20") frames with riders in the over 200# category, so even fully built with a crap-ton of batts, GK should still be under that weight load. With camelback and gear, I weigh in around 210-215- I put alot of miles on this frame at that weight with rear shock pressure set around 110-120 psi. I think my increasing the rear shock psi to 160 coupled with the increased weight on both sides of the shock assembly fulcrum (heavier rear wheel and heavier triangle/rider) caused my failure.
Thanks for the reminder that I need to edit the first post in the thread.Russell wrote:Very cool
So those are the largest and most powerful (48V/500W) versions of the Cute motors bmsbattery/ecitypower offer right? Any idea how fast they are supposed to spin at 48V?
The rear did not bottom out during the ride of death- the rubber o-ring marker shows the lowest travel point in my other pictures. That's not to say I've never bottomed this frame/shock before (several times actually), but not on it's last ride.GrayKard wrote:
Is it possible that the rear suspension also bottomed out at some point causing a huge spike in the pressure on that area? Or did the higher air pressure you put in the shock prevent that?
The fact that you put a lot of miles at a bit over 200 pounds with no problem does encourage me as even with my batteries and my usual gear I will be at about 170 pounds. The bike should come it at about 45 as I dumped the rear rack which was nothing but a headache.
GrayKard wrote:The test fitting of the motors looks good. Here's the front motor in:
Had to remove the paint inside the dropouts for it to slip in. I will also have to file a little to get the curve to match the axle and go all the way down.
Width was a perfect except the inside washers aren't on yet. I will have to spread the dropouts to get those in. I will be adding torque arms once the fit is right.
Now the rear motor:
This one dropped in without any tweaking. Yes that's an 8 speed freewheel in there. It will have the same spacing as the freehub once the washers are on. Same as the front the width was right on without washers. Very little spreading will be necessary to make it work.
I will need to radius the drop out to get it seat all the way but it's a much better fit than the front so won't need much persuasion. Torque arms here too.
Brake rotor fit is not bad. The front appears to line up but the rear will need some work. I will need to take off a bit of material from the rear bracket to move it out of the path of the rotor. But overall a pretty darn good fit.
The thing I was worried about the most, gearing, was no problem at all. But the dropout shape I thought looked to be easy will actually take a lot of precise filing to get the snug fit it needs. I'm a perfectionist with details like that though so it will get done right, just will take some time.
I also finally decided on and ordered batteries.
Two shrink tube 48 volt 12 amp hour packs from BMSbattery. Was more expensive than the bike due to the $156.00 shipping charge.
Mark_A_W wrote:And I fear you will encounter severe wheel-dish issues with such a big cassette, and the motor is not well designed for a big cassette - the spoke rim is far away from the edge of the motor.