Newby advice

[Inferno]

Hi, facinating forum!

I've been thinking for a while about making a bike with a motor to help with my daily commute which is about 15 miles. I'd like something which could get over 30mph if it could be achived.

I was thinking of using an Ampflow A28-400 DC motor (for its low rpm circa. 5000rpm) fixed to the downtube of a hardtail, mated to a flexible driveshaft that turns a bevel gear mounted where the rear brake rotor would usually be on your standard MTB.

The thing is, I'm no electronics expert (although keen to learn) and I see that the majority of 30mph plus e-bikes on here are running quite high voltage. The Ampflow motor isn't recommended to overvolted as far as I've read and that would limit me to 24 volts. With this type of set up would I have any chance of achieving my goals?

Also, is a motor controller strictly necessary with this type of motor? Or could it just be wired up in an on/off configuration directly from the batteries? (please be kind when answering this one!)

Any help much appreciated!

[recumpence]

Speed is not related to voltage, but wattage. Wattage is voltage times amperage. So, more power can be achieved at low voltage by upping the amperage. High amperage can be hard on the motor and controller, however.

Yes, you will definately need a controller. Any system with enough power to go 30mph will be a bit hard to handle with an on-off switch.

Matt

[rui_fujino]

I believe cheapest 30mph solution is 1000w 48v hub motor kits.
Those motor can be upgraded to higher voltage setup by just adding more voltage so you can keep them as future investment.
15miles both ways? Or 7.5miles one way to work....

[Inferno]

Thanks for the replies. It's 15 miles each way, including a rather large two mile hill.

Shame it'd need a controller, I want to keep the bike looking as bike like as possible - motor in a similar psosition to a water bottle, batteries in a back pack and a subtle drive line with minimal reduction gearing. I was hoping I could get up to around 15mph under my own steam and then just flick the go button.

I imagine a lot comes down to cost, but what sort of size am I looking at for a motor controller? The smaller the better, but I want/need reliability!

I've looked at hub motors, but I'm more in favour of direct drive.

[oldpiper]

Thanks for the replies. It's 15 miles each way, including a rather large two mile hill.

Shame it'd need a controller, I want to keep the bike looking as bike like as possible - motor in a similar position to a water bottle, batteries in a back pack and a subtle drive line with minimal reduction gearing. I was hoping I could get up to around 15mph under my own steam and then just flick the go button.

I imagine a lot comes down to cost, but what sort of size am I looking at for a motor controller? The smaller the better, but I want/need reliability!

I've looked at hub motors, but I'm more in favour of direct drive.

One thing you need to remember is that the power-to-speed relationship goes approximately as the cube of speed ( P = X*(speed)^3 ) because you aren't just pushing yourself along, you're also battling wind resistance, so it'll take you 8 times as much power to go 30 mph as it will to go 15 mph, especially uphill.

Combine that with the heat you lose to electrical resistance is proportional to the current, not the voltage (which is why high power lines are running megavolts), you are going to heat things up much more at low V/high A than the other way around, leading to failures, particularly in the controller department.

That's why most high-speed bikes are running at very high voltages, and you'd be much better off with a 48(+) V setup than 24 V. My hub motor (which around here is called a direct-drive, there are no internal gears) goes 25 mph easily, I could possibly push it to 30, but around here things are so curvy that I haven't. It's as simple electronically and physically as you can get, no gears at all (rear hubs are commonly made now to take a freewheel, so you can still use the gears for your pedaling, but I put my motor on a 1-speed bike). A hub motor actually can look as bike-like as any, you've just got a big rear hub, which can be hidden at least on one side with a disk brake. Good battery packs (LiPo gives you the highest power density, at the moment) are not too hard to camouflage, especially if you have a rear rack, or put them where the water bottle would go. The controller often fits on the seatpost/downpost or under the rack, and is all but invisible unless you are looking for it.

The other thing you need to consider is: Is your bike built solid enough to go at 30 mph continuously? Most probably aren't, and the high-dollar bikes are optimized for the driver pedaling, not motor drive, so they often aren't as good for an ebike as a mid-cost, lots-of-steel-and-good-welds bike (go through dogman's posts, he's had a lot to say on this topic). Don't get rid of your rear brake. Braking power is a Good Thing (TM).

Where do you live that they'll let you drive 30 without hassles? Most places don't bother you for 25, but 30 is pushing it for daily on-road use (and would be a terror on bike trails, so unless you want trouble don't even think it).

If you don't know electronics, just get a good kit from a reputable dealer and you can be sure that everything will work together just fine. Then, once you get more comfortable with things, you can start tweaking.

YMMV,

Cameron

[Brentis]

Thanks for the replies. It's 15 miles each way, including a rather large two mile hill.

Shame it'd need a controller, I want to keep the bike looking as bike like as possible - motor in a similar psosition to a water bottle, batteries in a back pack and a subtle drive line with minimal reduction gearing. I was hoping I could get up to around 15mph under my own steam and then just flick the go button.

I imagine a lot comes down to cost, but what sort of size am I looking at for a motor controller? The smaller the better, but I want/need reliability!

I've looked at hub motors, but I'm more in favour of direct drive.

Considering you will be using a BackPack.
You will not beat a rear hub for both,
Stealth & Reliability.
Hiding a controller is easy.
Rear hub motors can be hidden by a large disc brake & the freewheel cluster/derailer.
You cant get more stealth than that for cheap.

Also see Keplers drive.
http://www.endless-sphere.com/forums/viewtopic.php?f=6&t=34165&hilit=kepler+flatbar
I couldn't even see the drivetrain. Thought it was a before pic.

Got some cash & can build yourself. Try one of these. http://www.endless-sphere.com/forums/viewtopic.php?f=28&t=17090

I think Keplers drive is unbeatable for stealth. But comes with some limitations.
Maybe one of those cheater RaceBikes,
with motor in seat post downtube&batteries in top tube
Driving the B.B.
Couldn't find a link but very expensive.

With Battery BackPack.
Rear hub is stealth, very reliable, & cheap.

Welcome abroad the Sphere.

[Inferno]

That's why most high-speed bikes are running at very high voltages, and you'd be much better off with a 48(+) V setup than 24 V.

Many thanks for clearing that bit up for me, I knew there had to be a reason most of the quicker set ups on here running higher voltage. Also many thanks for the rest of your advice.

It appears that I have been hasty in discounting the hub motors, I believe I would be foolish to ignore the advice of the ES community who clearly know what they are talking about. And with my limited electronics knowledge a hub kit appears to be the way I should be going.

I'm in the UK and I'm quite confident that I'll get away with 30mph+ on my commute due to the type of roads I use - deserted back roads mainly! I wasn't planning on using it on the trails, quite happy with using my legs for that!

I've got a couple of bikes to chose from, a 2010 Whyte 905 hardtail MTB, or a 1996 rigid Kona Lavadome, although I won't rule out buying something second hand to convert. I think the lack of front suspension on the Kona would be an issue and the 10 speed rear cassette on the Whyte might cause hub motor selection issues? I would prefer the rear wheel to be driven, just because in my eyes, it's the right wheel to drive!

So any recommendations at to what kits to look at? The choices appear overwhelming!

[Inferno]

Considering you will be using a BackPack.
You will not beat a rear hub for both,
Stealth & Reliability.
Hiding a controller is easy.
Rear hub motors can be hidden by a large disc brake & the freewheel cluster/derailer.
You cant get more stealth than that for cheap.

Also see Keplers drive.
http://www.endless-sphere.com/forums/viewtopic.php?f=6&t=34165&hilit=kepler+flatbar
I couldn't even see the drivetrain. Thought it was a before pic.

Got some cash & can build yourself. Try one of these. http://www.endless-sphere.com/forums/viewtopic.php?f=28&t=17090

I think Keplers drive is unbeatable for stealth. But comes with some limitations.
Maybe one of those cheater RaceBikes,
with motor in seat post downtube&batteries in top tube
Driving the B.B.
Couldn't find a link but very expensive.

With Battery BackPack.
Rear hub is stealth, very reliable, & cheap.

Welcome abroad the Sphere.

Just wow! Kelpers drive looks fantastic! Thanks for the welcome and the advice

[Brentis]

Just in case you missed it, or for other Newbs.
See Hub motor bike builds here.
http://www.endless-sphere.com/forums/viewforum.php?f=6
For non hub drives/ mid drive hub builds see
http://www.endless-sphere.com/forums/viewforum.php?f=28

Also check in members signature for links to builds/trusted vendors.

Inferno, I don't want to talk you out of non hub drive.
With limited electronics/building skills, it is just the easiest, cheapest, most dependable solution.
Good way to get your "feet wet"
Then consider a second build with non hub arrangement.
Trust that once you build your first bike.
Your second wont be far behind.