Mid Drive Trike Conversion Project

[TheKraftyRhino]

I have been running this Aotema front hub now for close to 3 years on my Meridian Trike. Speed has never been an issue for me but power and range are essential. I have installed two programmable controllers that allows me to change between a speed and range setup to a low speed high power one. My major issue has been spokes and traction. Moving over rough unpaved roads puts the front wheel @ odd angles and off the ground a lot. I have looked @ some post where people have installed a hub motor to drive the rear wheels but I can seam to figure out how to go about it. I would like to install the Aotema with a gear to drive my rear axel. Can anyone help me figure out what I am going to need to attempt this and maybe direct me to some resource for mounting it on the existing frame.

I would like to mount a gear (or two) on the axel maybe one smaller toothed and one larger tooth then the drive gear on the motor so I can more easily change from high to low gear to get us started I have a pic of the space I would like to mount it.

 

[LI-ghtcycle]

Easiest way would be to mount the motor under the cargo area and run the chain to the hub/jackshft.

Would be better to have a pic or two of the trike showing a little more of it, not so much of a close up.

 

[amberwolf]

AFAICS, your best bet is to mount it in that triangle under/behind the seat, if it'll fit, and use a sprocket mounted on it to drive another mounted on the input to your rear drivetrain.

If the hubmotor has a bolt-on for disc brake on it's left side, use that to mount the sprocket to. Otherwise you may need to use a large chainring bolted to it's spoke flange, instead, and that makes it difficult to drive the rear with the ratio you'd want (small motor sprocket, same or larger drivetrain input sprocket).

I can't clearly see the drivetrain on the trike, but it looks like it has a jackshaft or an IGH that's being driven from the pedal chain, which then passes back to the trike's rear axle on one or both sides. That jackshaft/IGH is what you want to input your motor power to.

You could do it by having the motor sprocket mesh with the pedal chain, pushing the chain from the top, but without proper tensioners/guides at the pedal chainring in front, it may end up forcing it off the top of the chainring and make a tangled mess.

Alternately, you could run the chain from the motor to the pedal chainring itself, by adding a second chainring on the left side (just use an entire whole rightside pedal and chainring over on the left, in additon to the existing rightside unit). This forces pedals to turn whenever motor is running, but if you have the gearing ratio set so it's a comfortable speed, it doesn't hurt anything as long as your feet don't slip off, or if they do that you can let go of the throttle quickly, so you don't bash your calves/heels with the pedals, or tangle your legs in them. Stokemonkey basically does this chain path.

 

[TheKraftyRhino]

I uploaded a couple more pics hopefully that will give you a better idea.

The pedal Chain ring drives the mid hub that has what looks like a screw on freewheel on the right the middle chain ring is welded to the hub and not removable that then drives the chain ring on the axel shaft. The Contraption on the left side of the middle hub is a fairly useless band break the either never works or squeals so bad when used it pierces your ears.

I had considered mounting a freewheel on the right of the hub motor and a chain ring on the left and placing it in the rear dropouts but since it is a front drive there are no previsions and it would all have to be tapped out the motor covers.

Option 2 would be to buy a rear hub motor with a disk break option and mount a chain ring in place of the disk break. But i kinda would like to avoid having to buy another hub motor when I have one that is perfectly fine.

 

[LI-ghtcycle]

If you have a rear wheel hub motor, it would be very simple to just install it in the rear triangle area below & behind the seat and run a chain to the current hub that is acting as a jackshaft and then transfering power to the rear wheel.

A really nice option would be to place a NuVinci hub in place of the current hub and use it as a replacement for the one that is being used as a jackshaft now, and if it allows room for it, you would then have both a transmission, and mid-drive in a very compact area using all off the shelf parts minus the motor mounts, and you just put a freewheel on the NuVinci like you have one now on the current jack-hub, and since there are developer kits on sale for just $150 + shipping, it's a great time to get one.

One thing that many may not know is that Fallbrook Tech, makers of the NuVinci offers the manual cabling with the Dev Kit in case you want to just shift manually, IIRC, at no additional cost!

That would give you tons of options, but if it were me, and I didn't have a rear hub motor laying around to use, I would use one of these:

http://www.goldenmotor.com/

(Got mine shipped for $169, so really reasonably priced, just know it might take longer from China, or buy from GM Canada for about $200)

And the controller on your Aotema might even be compatable, if not get a Lyen 12 FET for $129 and you're going to have one amazingly efficient and powerful set-up IMHO.

I have used an Aotema at even just 36V with SLA's and it's a solid performer, so even if you're using 36V, I can tell you from experience that the 800W version of that trike motor I showed you is a winner, and the 650W on paper looks to be even more efficient, and should have similar characteristics, and would extend the range you get with your hub motor considerably, in my experience, it has been 60% more range on the same battery.

 

[TheKraftyRhino]

BLT 800 @ 48 V = ~1100 RPM

202cm tire = 79.52 in per revolution
1100rpm x 79.54in / 12 x 60 = 437470 Feet per hour / 5280 = 84.85MPH

I'm good @ math but that's not going to be the actual speed with 1:1 ratio is it? That's unbelievable I assume that is unloaded but in theory with enough power feeding it that would be the speed yea?

and that's according to there data sheet http://www.goldenmotor.com/hubmotors/BLT-800W%20Performance%20Curve.jpg
eff = 85.2
rpm = 1160
amp = 18.38
watt = 750.2
M= 6.18 N.m (Whats the mean?) if its Newton Meters that only like 1 newton metre = 0.7375621 foot pounds that means 8.37 foot pounds. Is that even enough to drive a trike with 26in 202mm tires?

did some research correct me if I am wrong

1 watt ≈ 44.25372896 ft-lbf/min
1 horsepower (mechanical) = 33,000 ft-lbf/min = 550 ft-lbf/s

So that 8.37 is @ 750 watts so 750 x 44.25 = 33187.5 making it just over 1HP motor @ 1160PRM ~18.38 amps?