mud's RC motor reduction unit/MTB bike build

[mud2005]

just went for first test drive and loved it! having the weight all in the center of the bike makes a huge difference. this is my first ride w/o a battery on a rear rack

the ugly wiring (red connectors) is the precharge resistor. I wired a pushbutton switch to the kill switch for the resistor and the wiring is a bit ugly so I'll fix that soon, but other than that I'm very happy with the way this turned out.

I'll have more info and better pics soon

thanks to everyone for helping me build this, this wouldn't have been possible w/o this forum

 

[mwkeefer]

Mud,

That is quite nice, very tight well placed and I'm sure the arrangement is far superior in terms of weight and power distribution (ok torque)...

I imagine with maybe 20min of tidying you will have a really nice, show quality bike!

Just curious... if you've geared taller than you ever go, won't that cause the motor to run in it's "inefficient" zone and shed heat (motor or controller or both)?

-Mike

 

[mud2005]

Just curious... if you've geared taller than you ever go, won't that cause the motor to run in it's "inefficient" zone and shed heat (motor or controller or both)?

it's geared for about 24mph and the pedals are 48/11 which is 71rpm cadence at 24 mph so I will be going full speed almost all the time

 

[dequinox]

Looks really good mud, all in one tight location right in the middle. Looks really heavy-duty so that it won't fall apart too! Can't wait to see it in person. Let me know if you are ready for a meet-up ride...although I've come to a point where I am not.

My lead acid pack is just about down to 4-5 miles even though it's a 18Ah pack... but there's some light at the end of the tunnel because I got a donation of about 250 2/3A cells from another ES member...and will be assembling it into a roughly 13Ah pack. They are nicad...but that should work for me just fine compared to lead!

Once again...VERY nice job on the reduction and the battery box! What kind of controller are you using again? Sensorless?

 

[mud2005]

Once again...VERY nice job on the reduction and the battery box! What kind of controller are you using again? Sensorless?

thanks, I'm using a Castle HV110 controller

sorry to hear about the demise of your battery. If you need a soldering gun to connect all those nicads I have a radio shack soldering gun thats brand new that I dont want, you can have it if you want it. I'm never buying from radio shack again.
It works, but it heats up quick and has to cool for a long time. I partially melted the side of the gun the first time I used it.

this is my first build with a Cycle Analyst. It's too cool! I may crash my bike cause I'm always looking at the screen
I took a ride today in the hills here's some stats from the CA:
5.175 AH
8.892 miles
26 volts (its a 24V 10AH Ping)
watt-hrs 127.95
wh/mi 14.4

that was up some really steep hills, I'm going to do some flat riding tomorrow to have some stats to compare

the bike tops out at around 21-22mph most of the time.

This battery has been sitting for over a year so I'm just glad it works ok

 

[dequinox]

Thanks for thinking of me on the soldering iron, but i already have a cheapie that works pretty well. I think it was from harbor freight. Nice stats on the analyst! 14.4 wh/mi is REALLY good for hill riding! Those little astroflights are very efficient! I bet the controller helps too.
Mine usually gets 25 wh/mi or so. I figured pretty good for an 80 lb ride and 240 lb rider

My battery is just old...lost most of its capacity. It will still give me a high speed run on a fresh charge, but it's a pain trying to go any significant distance. I got rid of my 24v pack too because I would hit the controller's cutout due to voltage sag. I have high hopes for these nicads though...the spec sheet lists a discharge curve of 8c! Though that is probably not recommended for any significant length of time...

 

[mud2005]

Mine usually gets 25 wh/mi or so. I figured pretty good for an 80 lb ride and 240 lb rider

yeah that is good, my bike is lighter and I weigh about 120lbs

had to take a break from riding after my girlfriends cat escaped from the vet's office. luckily after 3 days of searching we found him hiding in some brush near a creek.

anyway, I got back to riding the bike every chance I get and have had no problems until today. I was about 5 miles from home and the drive chain came off and wrapped around the rear wheel and I came skidding to a stop.
I yanked the chain out of the rear wheel and was able to ride it slowly home. I'm going to park it for a few days while I add a chain tensioner.

also the controller keeps hitting LVC. I think it's set at 3v/cell? that would make it 24v LVC which seems to be about when the controller shuts down when the battery sags to 24v.
I've yet to program my HV110. I'm going to hook it up tomorrow and check it out.
what should I set LVC to? the BMS has LVC and so does the CA, do I need to set the LVC on the controller?which is the best LVC to use or should I use them all?

 

[dequinox]

I don't know what the LVC for lifepo4 is off the top of my head, but it shouldn't be 3v! I think its more like 2.5v, but don't use that without checking with someone.

Glad you found the cat! If ours went missing my wife would freak!

Sorry to hear about the chain, I've had my share of those woes... I finally went with a combination of a drag-tensioner made from a highly wear resistant plastic and used a roller-blade wheel that i carved on a drill press with a shallow v-groove in it for the reduction tensioner. Of course you don't need a reduction tensioner so no problem there, but it seems to me you could drill and tap the batt. box and mount something to it easily enough. Remember to mount it so that it runs against the "return side'' of the drive chain, not the drive side. I made that mistake too... :?

 

[katou]

lifepo4 LVC 2.5v

A123 LVC 2.0 v

Go a bit higher for safety, say 0.3v

Katou

 

[mud2005]

Thanks

 

[katou]

Just re-read a bit more carefully. 3v is way too high for LVC. Most Lifepo (all the ones that I know of) sag quite a bit at C rates higher than 3c. I've been testing Moli cells, and I've tested up to 5c, and not many cells can even handle that. I'm not saying it's impossible, I haven't done the test to know. Just unlikely.

Here is a graph of Moli cells at 2c:



Notice how most of the cells cross the 3v line at about 60% State of Charge (SOC).

If you set the LVC to 3v, you would be missing 40% of the available energy in the cell.

Katou

ps. the CBA sets the cutoff at 2.8 instead of the 2.5 I want, but I'd have to change it for every test, and considering how little energy is left at that voltage, I just said to heck with it and left it at 2.8.

 

[mud2005]

got the chain tensioner working today. made it from an old skateboard wheel. the spring is from a surly singleator

 

[AussieJester]

Skateboard wheels are excellent ain't they! did you use the lath to shape yours or spin it on the drill press and attack it with a file ..?

KiM

 

[mud2005]

I used the lathe

 

[dequinox]

Nice job on the tensioner. I ended up using a file and the drill press, but you can't press on it too hard or the darn thing gets off-center. Lathes are handy, are they not? ;D

 

[jmygann]

I took a ride today in the hills here's some stats from the CA:
5.175 AH
8.892 miles
26 volts (its a 24V 10AH Ping)
watt-hrs 127.95
wh/mi 14.4

that was up some really steep hills, I'm going to do some flat riding tomorrow to have some stats to compare

the bike tops out at around 21-22mph most of the time.




what was your average speed ?

 

[mud2005]

I forgot to record the avg speed. I was going 20-22mph most of the time.

 

[mud2005]

I got a chance to weigh the bike today, it tips the scales at 47lbs.
it's an old chromoly frame and fork and I have added a bmx stem and bmx crusier bars. the bike itself might weigh close to 30 lbs. its listed as 28.2 online, but I've changed it a bit.

 

[dequinox]

Thats it?? Reduction + battery and all? Wow...nicely done!

 

[dequinox]

Hey mud have you finished this thing to a functional state yet? It seems to me you are probably commuting on it by now, or at least taking it for a joy ride or two. I've been thinking eugene should start a little 1/4 kwh ride or something. We'll see how far that pans out... In the meantime want to meet up for a ride?