Mongoose DX project

So, pretty addictive, huh?! :mrgreen:

I found that the fun really opens up when you hit 3kw. The bike goes from "Pedal Assist" to "Scooter" mode at that kind of power.

So, will you have any free time between school and your trip back home for the summer? If so, you could swing by and we could go for a ride.

Matt
 
That's what I'm planning on Matt. I'm officially done on May 15 and I'm sticking around up here for a few days so I'll give you a heads up.

John, JB weld is a good idea, but the magnets are quite difficult to pull out and reglue. If I have the problem for the third time I might have to do this however. What do you recommend for removing the magnets without damaging them?
 
IF you used superglue, then acetone will loosen the glue. It may loosen ALL of the magnets though. I would wait until they come loose again.
 
Congratulations, Oofnik on a successful test ride!

For your cooling fan, if you can find any dead power tools lying around, they often have plastic impeller-type cooling fans inside which can be butchered to fit on the end of your motor.
 
Finally:
[youtube]eMHvV_8W1W8[/youtube]

After the vid I let my roommate ride and unfortunately he got his jeans caught in the motor side. :shock: This managed to torque the motor mount again slightly so that the alignment was knocked out, so I had to realign it.

Milling the slots in the foot to fit over the screws should fix this problem.

Otherwise, all systems go. :mrgreen:
 
Someone mentioned "35 theoretical but probably 30". Where did you get the theoretical number and the "probably 30" number? It seemed like the bike was traveling pretty fast. And that acceleration was pretty impressive!

I have a feeling that drive-train efficiency calculations might have been skipped.
 
The theoretical top speed was calculated by measuring the motor's no-load top speed and dividing by the gear ratio and wheel diameter. No-load top speed of the motor is 8,640 RPM. The gearing totals to 17.5:1 With a 26" wheel; this comes out to about 226 motor rpm per mph. 8,640 / 226 = 38 mph. With wind resistance and rotational loss fudge factors I arrived at 30 mph.

Drivetrain efficiency.. hmm let's see. Brushless motor: assume ~70% efficiency typ. Belt drive: assume 96% efficiency. Chain drive: 94%. .7 * .96 * .94 = 63% total efficiency. At 3000 W electrical that's about 1,900 W mechanical. Yet to be confirmed via kinematics / dynamometer (one of these days).

I'm not building a rocket here. Fudge factors are okay. :D
 
Ah, ok. I just ran some of the numbers in my calculator and it seems to predict between 33(just starting off) to 31 mph. Since it doesn't take into account drive-train efficiencies, you'd probably get something like 28-31 mph in real life which seems agreeable with your observations.

Anyways, I hate to gloat, but I'm finding it like a miracle how much my calculator agrees with real life. :lol: Which isn't to say I'm bad at making simulators, but I expect "simulators" in general to be off by 20% or more for complex systems.
 
oofnik,

Very nice! You've got me even more excited about getting my current project done.

Since I'm using the same motor and controller I'm curious if the HV85 is getting very warm at all? Also, I'm not sure if you've been following my thread but I'm currently getting ready to glue around the magnets on my 5330. How hot would you guess your motor is getting? Would you say just warm or fry an egg hot?

Again, great job!
 
Awesome video, your acceleration is phenomenal! 8)

Are you guys taking into account the drag produced by the afro? :wink: That's at least gotta take off like 2-3 mph.

Just kidding Oof, I'm just jealous you already have your bike going. Maybe you should look into leg protection from the chain, can you imagine if you were going balls out when your jeans get caught! :shock:
 
EVTodd, it gets up to about maybe 140-160 F (guesstimate) after 10-12 full acceleration launches. This was on a day when it was about 80 outside. Under normal usage I don't expect it to get hotter than 40 F over ambient. That's going to be even less when I fit the fan I ordered from Astro Flight.

I have been following your thread. My motor is the 10T - I'm not sure if you will see significant differences but I would doubt it.

I mounted an external heatsink on the controller that fits in the groove on the bottom - there's a picture on page 9. The controller gets warm to the touch after the launches, maybe 110 F. Should stay barely warm under normal usage.

Where are you in IL?
Looking forward to seeing your progress!

etard - #@%# I don't want to think about that :shock: I've been thinking about putting a chain guard on, but it would be an issue finding a solution that looks halfway decent. Maybe just some simple sheet metal bent around the freewheel and the top of the chain? I'll come up with something.
The afro, well, I'll take some tests after I get a haircut and we'll see. :D Back in high school the first thing my physics teacher said to me after I got a hair cut was "wow! you look aerodynamic!" :mrgreen:
 
Here's some clean data of RPM, amps and watts from the ride I just took. Peak power in this interval is about 2 kW. Top speed taken from a clean sample in this interval at 1593 sec. is 6613 RPM / 226.25 = 29.2 MPH.

The brushless sensor is awfully noisy. I'm not sure why. I should contact Eagle Tree about this.
data.png

As far as heat, after normal riding the motor is very warm to the touch but not fry-an-egg hot, and the controller is slightly warm.

I'm still having it cut out occasionally as I pull >100 amps. It also tends to hit the LVC if the battery is more than half empty and I launch it. An actual active current limit would be nice...
 
So uh, this happened today:


I knew something was too good to be true here. :(
The drive kept getting more and more out of alignment no matter what I did until the chain wouldn't stop falling off. I had to carry the damn bike on my shoulders for a few blocks home because I couldn't roll it without the chain getting caught.
Good thing I'm not using lead... :shock:

I put the drive back on and aligned it. Now it doesn't sit flush against the screws, so it's probably going to slip.
Batteries are charging now so I'll find out for sure later.
On the bright side, I pulled 9516 mAH out of them from a full charge. That's pretty good. :) Plus I got my Hong Kong $1 bike odometer in the mail today and tested it out. Seems to work alright.

The mounts must be improved. I'm thinking flat bar stock, counterbored, screwed in to the frame so the heads sit flush, then welded.
 
Hi,

I think if you drill or mill holes or slots in the bottom of the foot, to fit over the bolts it will probably work.

The pressure of the foot will be supported by much more of the frame so I don't think the frame will crush.

The bolts will massively increase the resistance to rotation and twisting rather than making movement almost impossible to prevent.
 
Hi,

The mounts must be improved. I'm thinking flat bar stock, counterbored, screwed in to the frame so the heads sit flush, then welded.
Click to expand...

But I think for an even more secure mount I'll do the counterbore thing.
Click to expand...

Do you plan to continue to use the clamps? Because I don't think the 2 bolts are enough.
 
So I rode around today and sucked down another 9.3 AH in about an hour. :twisted:
The motor didn't slip at all. The clamps are holding up. Yay! I think I'm going to still do the flat plate idea though as soon as I'm done with the semester. That with the t-bolt clamps should be virtually bulletproof.

On another note, the batteries are getting up to about 140+ F in their sealed case. I'm pretty sure that's not good. I think I'll mount a nice big heatsink on one side of the box (probably the bottom) to transfer heat out of there while still keeping it water/weather proof. Maybe even just a big Al plate will be enough to act as a "heat window".

I received the fan I ordered from Astro Flight. It's not quite big enough, and it doesn't quite fit, and I don't have quite the right drill bit, so I'll have to wait to get it mounted. But it should help at least a little bit. The motor got pretty effing hot today... I need to watch that throttle.

I'm also considering building a 12s1p A123 pack to supplement the Headways. Just enough to help them out and increase range just a bit. If I can find 12 cells for the right price I'll do it(PSSST Doctorbass! :mrgreen: ), but for now that'll wait at least until the summer. Do you guys think I'll have any problems doing that?
I'm probably also going to build a modified Fechter current limiter circuit to replace my servo tester, because the BMS cutting out is really getting annoying... it's either that or blow stuff up though so I'll take the cutout for now.
 
Hi,

oofnik said:
I'm also considering building a 12s1p A123 pack to supplement the Headways. Just enough to help them out and increase range just a bit. If I can find 12 cells for the right price I'll do it(, but for now that'll wait at least until the summer. Do you guys think I'll have any problems doing that?
Click to expand...

I don't know if he still has any but if so this is a good price for new cells:
http://www.endless-sphere.com/forums/viewtopic.php?f=14&t=9404
A123 Cells Welded into custom configs $6.50 per cell

Posted" Sat Mar 28, 2009 1:21 pm

To all who are interested:
I was informed that this pricing will not last, the shipment from which I am receiving these was purchased directly after the GM contract went south and A123 needed quick capital. They have now returned to their pricey ways.

I can't say how long these will last at this price. So if you want them now is the time. Current pricing is $6.50/cell assembled, pricing could go to anywhere from $12.50 to $16.50/cell assembled. I can say that I am setting up an automated,(CNC Weld Head), system. I would be able to assemble your cells in any configuration with very good accuracy and quality control on all the welds. All modules will be set up in hdpe casing to allow easy mounting. Terminals will be 5/16" for connecting the modules in series. Let me know if there is any way I can help you in your battery pack needs.
Click to expand...

Several forum members made purchases and I think they are happy.
 
Another brain fart - I'm thinking when I get back home to Atlanta, I'll replace the freewheel with a track cog and enable brake a.k.a. regen on the CC controller. This will allow me to take advantage of the hills we have down there. However I'll need to beef up the idler so that it can support a load. Are any of you guys running your Castle controller with brake / regen enabled? Any opinions?
 
I don't which setting of "brake" corresponds to "regen", but I know that the "brake" feature on mine made it squeal as if it was going to break whenever I forced the scooter forward.
 
Offnik,

I haven't run regen yet, but I found something interesting;

Yesterday I was test running my twin motored bike. I found that if I run one motor and controller with the other controller disconnected from the battery, the back feed power caused the second controller to power up! It was weird. I was merely running on one motor and all of a sudden the other controller armed.

So, backfeeding power into these controllers does send current to the battery leads............

Hillarious! :mrgreen:

Matt
 
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