How much "power" do I really need?
- Thread starter HappyNaturalist
- Start date
I have 1000 watts, and it gets over some super steep streets. With me helping of course. That extra power is so nice if you live in a hilly area. At my age, 75, I'm having lots of fun not stressing the hills or the range. I carry a second battery on the back. Just know, anything over 750 watts is no longer a bike and needs to be registered as a scooter where I live. Probably the same where you are. Just be careful around others. Good luck.
spokewrench
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- USA
In 2020 I bought a Radrunner after studying an EBR video that showed its performance. Mine was disappointing. I checked the specs: 750 W and 80 Nm. On a 10% grade I found that I was getting 2/3 of that torque. On a 6% grade I found I was getting 2/3 of that power. What's more, when I studied the video again, I calculated that they were getting much more torque and power than specified.
They claimed 750W and 80Nm because that's what Bafang specified for the motor output. Bafang must have specified a 25 amp controller. Radpower must have used 16 amp controllers for OE and 35 amp controllers for their demovid. With the OE controller, I would have had to push the bike up anything steeper than 10%. A 35 amp controller gave me ample torque and power.
That was a geared motor. I've also had three direct-drive bikes. The 750 and one of the 500s came with plenty of torque. The other 500 was from Radpower. I found that it was producing only 350 watts. As with the Radrunner, the OE controller was too small for the advertised mechanical output. A 25 A controller gave me more than 700 W output on a hill. For my purposes, the torque and power were as good as what I got from the 35 A Radrunner.
Air drag becomes significant at 15 mph and increases with the cube of speed. I don't go much over 20 on the level and am usually not over 15. I guess that's why if a motor can put out 700 watts, that's plenty, provided it can produce enough torque. Adding poles can increase the torque of a direct drive motor.
They claimed 750W and 80Nm because that's what Bafang specified for the motor output. Bafang must have specified a 25 amp controller. Radpower must have used 16 amp controllers for OE and 35 amp controllers for their demovid. With the OE controller, I would have had to push the bike up anything steeper than 10%. A 35 amp controller gave me ample torque and power.
That was a geared motor. I've also had three direct-drive bikes. The 750 and one of the 500s came with plenty of torque. The other 500 was from Radpower. I found that it was producing only 350 watts. As with the Radrunner, the OE controller was too small for the advertised mechanical output. A 25 A controller gave me more than 700 W output on a hill. For my purposes, the torque and power were as good as what I got from the 35 A Radrunner.
Air drag becomes significant at 15 mph and increases with the cube of speed. I don't go much over 20 on the level and am usually not over 15. I guess that's why if a motor can put out 700 watts, that's plenty, provided it can produce enough torque. Adding poles can increase the torque of a direct drive motor.
Yes. 20 is fast enough on the flats for sure. It's those big ass hills that get in the way. Lol
I only use 25 mph where the pavement is superb & there is no water or ice at the bottom. On average, I ride 8-10 mph. I'd have to have a suspension to enjoy going faster than 10 on our typical pavement, and suspensions are not compatible with carrying groceries to my summer camp.
I only use 25 mph where the pavement is superb & there is no water or ice at the bottom. On average, I ride 8-10 mph. I'd have to have a suspension to enjoy going faster than 10 on our typical pavement, and suspensions are not compatible with carrying groceries to my summer camp.
spokewrench
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My Radrunner was terrible on bumps. At 30 PSI, those wide tires were stiffer than other tires at 60 PSI. A suspension post and seat with springs made little difference. A worse problem was that the handlebars were at belt height and not far ahead of my belt. That made my upper body unstable and thus the steering dangerously unstable.
It was much better after I moved the seat back to get it away from the bars. Comfort on bumps was an unexpected benefit. Instead of sitting erect, I was leaning forward, a bit like standing with my butt against a wall for stability. My legs were absorbing most of the bump energy, and they did it better than my spine.
Wrist shocks were still so bad that apparently I tore a tendon. It felt as if I had a broken bone in my wrist. It finally dawned on my that I could use a riser to raise the bars a few inches. Raising the bars meant less weight on my hands, and my arms were freer to swing on bumps instead of transmitting shock lengthways.
I also bought different bars to change the angle of my wrists. It still had stiff tires and no suspension but was now comfortable on bumps. My legs could lift my butt, and my wrists could "float."
The photo shows my position with the seat back 7 extra inches on a layback post, braced with a plywood triangle. Leaning forward to put weight on the pedals took the weight off the seat, and that meant comfort. However, these bars were too low, not letting my arms swing up to float over bumps.
It was much better after I moved the seat back to get it away from the bars. Comfort on bumps was an unexpected benefit. Instead of sitting erect, I was leaning forward, a bit like standing with my butt against a wall for stability. My legs were absorbing most of the bump energy, and they did it better than my spine.
Wrist shocks were still so bad that apparently I tore a tendon. It felt as if I had a broken bone in my wrist. It finally dawned on my that I could use a riser to raise the bars a few inches. Raising the bars meant less weight on my hands, and my arms were freer to swing on bumps instead of transmitting shock lengthways.
I also bought different bars to change the angle of my wrists. It still had stiff tires and no suspension but was now comfortable on bumps. My legs could lift my butt, and my wrists could "float."
The photo shows my position with the seat back 7 extra inches on a layback post, braced with a plywood triangle. Leaning forward to put weight on the pedals took the weight off the seat, and that meant comfort. However, these bars were too low, not letting my arms swing up to float over bumps.
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That setup looks painful. With no front suspension you feel everything you go over. Nothing to absorb the rough roads. I wanted my bike to be comfy as possible so I added a riser and Jones H bar to allow my arms to be higher up and back. Much better ride. Here's some photos.
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indianajo
Well-Known Member
No 20" wheels for me. Been there, done that, 1957-61. I ride 26"x2.1" tires at 55 psi. Cargo bike, no suspension, no seat post spring, everything feels fine up to 4 hours. My hands & wrists go numb before my back & neck hurt.
I second bithigh's experience, 8 mph average is fine. The extra 250 watts over legal limit is to maintain that speed up 12% grades with 330 lb gross. I'm only 160 lb. 80 lb of 330 is groceries, ag chemicals, lawnmower fuel, tire, tubes, tools, rain gear.
I second bithigh's experience, 8 mph average is fine. The extra 250 watts over legal limit is to maintain that speed up 12% grades with 330 lb gross. I'm only 160 lb. 80 lb of 330 is groceries, ag chemicals, lawnmower fuel, tire, tubes, tools, rain gear.
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spokewrench
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Here's what a riser did for me on my Radrunner. I'd say the bars were now 10" above seat level, which was typical of how riders adjusted classic 3-speed commuting bikes (although those bars had a better wrist angle).
My forearm was almost level, so a little elbow flexing would let my hands float with the bars. By suddenly retarding forward motion, a bump also causes the rider to lurch forward relative to the bars. In this position, flexing of elbows and shoulders would absorb that, too.
My Abound came with a front suspension and something like 10" of height adjustment for the bars. After several months, I locked out the suspension out of curiosity. The bumps were sharper, but the riding experience was virtually the same because the shocks weren't transmitted through hands, wrists, and arms.
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kevinmccune
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so you figured the riddle of wide tires too,congradulations,used to drive a dump truck with "wide floaters" on the front, beat you too pieces.
I retired from trucking in 2000. I pulled double tanker trailers that had those super single tires on them. Those things made me nervous. With dual tires, the second tire will keep the load upright. But blow a super single with 105,000 lbs. load and that liquid load could roll. Never noticed the lack of comfort, the tractor had normal duals. My bike has balloon type, not the fatties. Good ride.
kevinmccune
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the floaters i refer too are those heavy duty 65 mph things that cost way more than an 11.00,things would beat you to death and when the alingment was bad these things let you know it.
The wide tire was suppossed to be lighter than the duals thus saving on fuel. The discomfort and worry to the driver was secondary. On bikes I fail to see the advantage of the fat tires.
kevinmccune
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as much as i dislike them they seem to be a bit better in the rough,i noticed my 27.5 bike handled better then the 26" bike with narrower tires on my "hell trail"( finally had to abandon it-its the only place i liked to ride around here,17 mile round trip) had a guy comment yesterday that the trail bikes have destroyed the road( part of the eastern trail) i agree.
