Giant ATX 450watt - budget build

[veloman]

(go to 2nd post for first test run and pics)

This is my second ebike build. My first used a 24v system and 600w Currie scooter motor mounted near the back wheel, driving the left side spokes on a single speed road bike. I'll attach a picture of that as well.

Lesson's learned on first build:

1) Motor placement restricted normal pedaling too much (too close to left rear heel).
2) Motor mount wasn't adjustable, or strong enough to be reliable. Couldn't adjust chain tension.
3) Singlespeed bike design coupled with the above motor mount, meant a huge headache trying to get both chains properly tensioned.
4) System was geared for flats, and had no torque for moderate or steep hills. Going into shallow hills at speed (25mph), along with pedal assist, the bike did fine. But any sustained hill was too much. Acceleration was very poor until >15mph for the same reason.
5) 27lbs of tall SLA batteries on the rear rack hurt bike handling a lot.
6) 27x1" cheap tires did very poorly with such weight on rear wheel.

Other those drawbacks, it was a fun ride on the flats, cruised at 25mph for 10 miles. 2x17ah batteries.
My main issues I wanted to fix on my second build are # 1, 2, 3, 4, and 6. Wow, that's a lot of improvement if I can do it!
Reducing battery weight will be hard wthout investing in expensive Lithium or such. (But it may happen).

So here goes the stats on my 2nd build - A Giant ATX 760 rigid mtn bike from 1996. BEAUTIFUL bike, I love this thing. Got it for real cheap off craigslist last week. A very sturdy, steel, strong bike for such a project.

- 36 volt system
- 450 watt geared motor (MY1018) with bicycle chain sprocket. Shaft output of about 420rpms max. 5lbs
- Battery: 3 12v x 12ah for 36volt, VRLA batteries. It's some sort of SLA. Weight 22lbs in plastic case.
- 36v cheap scooter controller
- Cheap thumb throttle
- Crankset - from sickbikeparts, freewheel cranks, currently 44 tooth driving rear cassette (13-30), and 36 tooth driven from motor sprocket - 9 tooth. Will be switching to 30 tooth this week due to clearance issues with frame.
- 36v 1.6ah charger

Total cost of above list (no bike): around $220 shipped. I spent more due to changes I've already made.

Total weight of the bike should be about 58lbs once I swap out these heavy mtn tires for 1.5-1.75" slicks. I'm looking for a usable range of 15 miles with very little pedaling (starts, hills). If I like how the bike runs, I will likely try to do a Bosch Fatpack additional battery pack and charger to extend range, or for short trips of 2-3 miles to the store.

The thing I loved about the first build was that it was soo quiet. I am worried that this geared motor I'm using is going to be too loud, but we'll see. If I have to switch back to a non-geared motor, I will need a reduction unit of about 7:1

I'll attach what pics I have so far. The stage I'm at right now is halfway done with building the motor mount plates which are going on the water bottle holder mounts. I have an ingenious idea for the battery mount on the rack - pics to come tomorrow likely. I hope to get this finished tomorrow, with more corrections to be made by weeks end. The weather is beautiful here in Austin TX and I don't want to drive my car anymore! :lol:

Pics for 2nd build will come tomorrow, current ones are too big.

 

[veloman]

The air was a balmy 70 degrees, the gusty wind commanded leaves to chase me, 500 ft above was a chopper going my direction, clearly chasing me over these deserted suburban roads in the middle of the night.

The Giant ATX rode beautifully! It beat my expectations. That little 450watt geared motor has some balls, when you're in the right gear. I currently only could use the top two gears on the cassette safely, as I have the front chainrings mounted too closely together due to clearance issues with the large 36 inner ring (which will be changed to either a 24 or 30 that is coming in the mail this week).

Sound: the motor wasn't nearly as bad as it was compared to running it with no load. It still is a relatively loud electric motor, you'd hear me coming from 200-300 feet or so. But it's still nothing compared to an ICE. But I am very happy that I can live with this noise, which will be even relatively less during the daytime with cars on the roads. (Things are quiet here at 1am).

Motor mount: it has worked flawlessly so far. Very strong and rigid. I spent so much time perfecting the best I could with my measly power drill and dremel and hacksaw. Oh yeah, the motor barely even gained any temperature after 8 minutes of moderate-fast riding, that's a good sign.

Range: tomorrow I will do a test to get an idea of the range. I don't want to damage the batteries, so maybe I'll end it when power drops noticeably?

Battery mount: I use a $6 plastic container from Lowe's, the 3 batteries fit perfectly in there, about 5" x 12" x 4" high. I bolted that straight onto my aluminum rack. Then I put a bike tube with a little air in it, in the bottom and around the back of the remaining space in the container. This keeps it secure and adds some cushion. I may switch to using some sort of pipe insulation which may cushion the bumps better. That's my only drawback, is the weight of the batteries going over bumps. It sounds bad, but shouldn't be hurting anything. The plastic container closes and in case of rain or water, the batteries will stay completely dry. (Maybe a small case for the controller on top?)

Below are all the pics I took tonight. I need to make a few refinements such as cleaning up the controller and wires.

Update: I took it out this evening for 14 windy miles through the relatively hilly area around here, with a lot of stops, about 15-20 stops. The motor definitely isn't enough by itself on anything steeper than 2%, which is kind of poor, but it's only 450watts. I didn't go any further, but the batteries didn't feel like they were dropping yet either, which was a great sign considering I got in 14 miles with some pedal assisting. The roads around here are slow chip seal, and I'm still riding the knobbie mtn tires. I think the batteries are indeed 12ah each, or a total of 432 watt hours.

There only seems to be 2 or 3 levels of throttle control. I wish I had a monitor to tell me what my wattage was and battery capacity. CycleAnalyst right?

The motor is still louder than I would like....but I can live with it. Eventually I am going to look into getting a reduction unit and one of the 36v 1000w motors that aren't geared. Would be quieter.

Today was just a slow day for biking. I was out on my roadie earlier and the wind was really dragging me down. This bike should be fine on the flats with less wind.

More updates:
Today I did a bunch of errands on it, in a less hilly area, smoother roads and less wind. It did pretty well. Oh yeah, I also switched to a 30 tooth motor drive sprocket on the crankset, instead of the 36. That allowed me the proper clearance with the frame, and bike chain, so that I could use the entire cassette now. It seems to be perfectly geared with the 13-30 cassette. It has remarkably good acceleration from 2mph on up. I thought of getting a cassette with an 11 tooth gear, but I won't ever use it since I coast when I'm above 25mph on downhills usually. It's just a simple commuter, no speed demon.

I got some parts to build a chain tensioner off the motor since it seems I could use one, which should cut down the noise a little. I'm also going to transition over to slick tread tires now, which should give an automatic 1-2mph increase. 1.25" in front and 1.75" on the rear. I may also switch to a grip throttle, or rig some cruise control up for the long stretches of flats.

I'm liking my bike a lot more today than yesterday, just realizing it's not meant for high power riding. It does the job well of commuting at average speeds of 15-20mph (depending on stops).

More Updates:
Still haven't found it's true range, haven't had to go more than 10 miles yet, (did 14 that first day). Chain seems to still be noisy, the tensioner is keeping it secure and snug, but adding noise I think. Chain got looser too, motor must have shifted.

A few days ago I took the bike up a 19% grade, short, only 200 feet or so. I had to put out 1000watts myself in addition to the motor in order to quickly get up it, dropping to 17mph at the top. Not the sort of bike for 19% grades, lol.

Still thinking of ways to cushion the batteries better over bumps. A full suspension would help a lot on rough roads, but how to mount 22lbs of batteries on one?

I'm brainstorming my 3rd build already. Full suspension bike. Going to mount that 1000w scooter motor on the rear disk brake mount, bolt a sprocket to the rotor, use a #25 chain. Direct drive, quiet, efficient. Only downside is loss of torque on hills and starts. But the larger motor will do much better, and I can still pedal. Cruising will be much nicer with a quieter motor and smaller chain. Full suspension with 1.25 or 1.5" slick tires. Cushy, but efficient. Only downside is less range if I end up cruising at 25mph vs 20 as I do now. 20 is still decent for commuting. Technically with the 1000w motor, I could cruise 30 on the flats. Pretty sweet deal. Maybe motorpace the roadies...lol.

Oh yeah, I ordered a Bosch Fatpack and charger this week. Going to try wiring that up so I can drop that lead weight for my short 2 mile round trip to the store. If all goes well, will order more Fatpacks for range. Maybe carry them and the SLA's for ultimate range.

 

[02jze]

How do these motors go with using the larger sprocket ? mine has like a bmx sized one and i wondered about changing its size.

 

[veloman]

My motor has 9 tooth sprocket on it, works well. A 16 would be too big, unless you were driving a 45-53 chainring on the crankset.

Mine's geared perfectly for the motor's ability. (well, for non-hilly areas).



Here's some pics of my 2nd battery pack holder - so i can detach them in 30 seconds to bring them into work to recharge. I don't want to leave them at 80% for 8 hours each day. Carrying 25lbs into work is a good core muscle workout too.


The bike has been doing well. 110 miles on it. It handles much much better than my 1st build. The wider tires are crucial.

I did do one short ride with the 3 Fatpacks. Wow, it handled like a normal bike, and it had noticeably more power. very nice.
I need to wire up an interface for the Fatpacks. I have it wired now, but it's not removable, so I can't charge them without untaping everything. I will use both SLA and these for my long trips over 15 miles (rare).

 

[donob08]

veloman

..I like the simplicity of your build. But I don't think it would work for me. It looks like you have a Unite MY1018 motor that wants to run at 550 rpm WOT. When you had the 36T drive chain wheel it was 550*9/36 = 138 rpm at the crank. When you switched to 30T it would be 550*9/30 = 165 rpm at the crank. You must be a spinning machine.

..Keep us up to date on your racing career .

Don

 

[veloman]

You're right, the cranks are geared a bit off for WOT. Like when I'm in my 30tooth in the back, going up a hill with 3/4 throttle, I'm spinning kind of high, definitely too high. I really need a wider bottom bracket so I can mount the 36 back on, or maybe even something bigger. But I don't pedal 90% of the time either, so it's okay.

I tested the motor with rear wheel lifted off the ground and got 46mph in my 13 gear in back, which is 4500 rpms. Apparantly it's much higher than the 3000rpm it's listed as. The motor seems to operate best at 1500-2000rpms for normal riding. I like to use whatever highest gear I can that allows it to accelerate with additional throttle. If I'm revving it near it's max, it whines a lot. If i'm overgeared, it will chug which I'm sure is bad for it.

 

[veloman]

So I changed the front cranks to the first setup. 9x36 for motor, 44x13-30 for bike chain. But I put a longer BB spindle in for better clearance and now have the 44 on the inside for better chain line. I had to redrill the motor mount holes.

Pedaling is much better now, at normal cadence. With max throttle I should be at 100rpms, so it's perfect. I ride at the max of the motor's capability about 50% of the ride lol. It's only 450w rated.

update:
motor gear of 9x36 lowers top end significantly, even when compensating for the difference by using a smaller cog on the cassette. Low speed riding is better though, up to 15mph. It's a big riddle as to why this is.

 

[veloman]

Added 2 more fatpacks. Now I got 20 miles range with 13lbs of battery, which is also capable of a lot of amps when I get the new motor on there.


I pedaled a 1987 Bianchi road bike to work today, just 1.6 miles. and then .5 mile to lunch in my work clothes up a 50 foot shallow hill.

Commuting and pedaling suck. I completely understand why so few ride normal bikes to commute. I do ride my fast road bike in spandex when going to my gf's 20 miles away, that's more like a normal road ride. But wearing work clothes (business casual) and biking in this humid heat.....suckss..

Can't wait to ride the ebike tomorrow.

 

[gogo]

I pedaled a 1987 Bianchi road bike to work today, just 1.6 miles. and then .5 mile to lunch in my work clothes up a 50 foot shallow hill.

Commuting and pedaling suck. I completely understand why so few ride normal bikes to commute. I do ride my fast road bike in spandex when going to my gf's 20 miles away, that's more like a normal road ride. But wearing work clothes (business casual) and biking in this humid heat.....suckss..

Can't wait to ride the ebike tomorrow.

Amen. Plus those slacks will wear the hair off your knees if you pedal. The 450W motor must be wound for 3000 RPM @24V, so if you're running it at 36V its a 675W motor.

Thanks for posting your build, its some good info. about the Unite motors' performance. It looks like your controller is 30A so you're pulling about 1000W max. out of the batteries?