The Linear (recumbent) Booster

[EVTodd]

I know I say this every time I see a thread about friction drive, but... You can save a lot of trouble by not making a spring activated system to raise and lower the roller if you use a roller with a clutch bearing so it freewheels when not being driven by the motor. The cheap route is to buy an ev warrior roller with the bearing already in it. Here's a link:

http://cgi.ebay.com/2-EV-Warrior-Electr ... 286.c0.m14

I'm currently using one at 36 volts which on my bike with a friction drive Kollmorgen gets me 22 mph with pretty good hill climbing.

[lawsonuw]

First update: Winter commuting. My Marin/Cruzbike is a bust for now. I'll continue learning to ride it when the snow clears . In other news my Linear now has full studded tires! Had to mod my repairs to get room for the tire in the back, but everything fit nice. Have to run funny air pressures in the tires 20psi in the front, and 45psi in the back. I'm going to see how well 70psi works in the back next.

Now on to the picture below. It's a little toy I hacked together to test belt tracking. With the belt and crowned pulleys from SDP-SI the belt tracks true when the big pulley goes clockwise, and runs a bit off center in the other direction. Also looks like the belt has enough stretch that a fixed idler will be fine. If I add some flex in the right spots it should also be able to shrug off sand and grit.

Now the juicy bits. It's about a 15:1 (81.5/5.5 to be exact) reduction in one stage, and COMPLETELY silent. I could easily use this for the first stage reduction for a 40krpm plus motor. Current plan is to scale it up a bit and use my other motor and a ~20:1 belt to drive my linear. Not sure how long the belt will last, I am pushing it a beyond it's specifications but I'm staying well clear of it's breaking strength. I've got some other belt ideas up my sleeve if I shred this belt. Best of all, I can make my own pulleys for this!

Marty

[liveforphysics]

I Love this thread, it love this bike, and I want to know how your new pulley setup worked out!

[lawsonuw]

At the moment the pulley setup is on hold. I've got 2/3 of a design for it done. I need to fill in the last details and do a design review. But, "minor" things like getting a job or getting into graduate school are sucking up all my time.

I have done some upgrades to the base bike though. It's got a front fairing, this is primarily for rain/wind protection. The other thing keeping this on the back burner is that I'm getting into better shape! so doing my commute on leg power alone is less of an issue. I've attached a picture of my new fairing with poncho attached. i.e. ready for RAIN.

Lawson

[greygandalf]

Hi, I think your recumbent mod is brilliant!
If you see this post, maybe you could post an update? You were changing the setup to use a belt.
Were you intending to use a toothed belt or not? Interestingly, trek have made an urban bike with a belt drive (internal hub multi-gears).
I have a question about the motor you used (Turnegy - SK42-50-650) . It would seem that this motor is "intended" for use in model aircraft - as such it would get plenty of airflow to keep it cool. Did you find it got hot in use? Was being exposed to the elements ever a problem (for the motor that is!)? ie did it ever get wet ? I have an application, in a boat, where it may be enclosed (or get a bit wet!), so might have to consider some cooling. Thanks.

[racegun]

this is an incredible thread! Thanks for all of the posts and information. I am looking into doing the exact same thing when i buy my linear in the next few months.

I have a few questions

1. Y are you all choosing that kind of motor drive as opposed to a direct drive hub motor? Cost, efficiency, things that I have yet to learn..etc?
these come to mind http://www.electric-bike-kit.com/hill-t ... 7AodYBwNYQ & http://www.ebikes.ca/

2. I am looking at the linear limo3 or the linear roaster swb. Would a SWB lend it self as well to electric boost as a LWB?

[lawsonuw]

I chose a through the gears drive for two main reasons. I wanted the drive system to be light enough that I could still pedal the bike easily, and I wanted enough torque to winch me up steep hills. (there was also a fair component of seeing if the crazy plan would actually work)

I don't think SWB or LWB is particularly better for electrification. I find a LWB bicycle easier to handle in tight places and stop-n-go traffic. On the other hand my Performer High Racer is a pedal powered rocket (it has a very reclined back seat) and would have impressive speed/efficiency if electrified. (i.e. ~300 watts would propel the Performer at ~30mph on level ground) The linear is especially nice for electrification experiments because of the extruded main tube, the screw on clips make for a clean install.

I am currently tempted to make a traction drive system for my Performer. I'd pattern it after one of the several small friction drive assists described on the endless-sphere. Having a light 1000-1500 watts "turbo" button would just be heaps of fun. (and true to the "turbo" concept, I'd size the battery for at most 5-10 minutes of power) The "turbo" button would also let me make better use of the human engine. I.e. I'd let the "turbo" handle any power spikes, while I contributed the bulk of the energy for a ride at a slow and steady pace.

Regarding RC motors and overheating. I'm not too worried as I was never pushing the motor very hard. Also I rarely used the motor for more than a minute at a time, so it had plenty of time to cool.

Lawson

[racegun]

lawson,
are you saying that a direct drive hub motor powered bike will be harder to pedal than if said motor was not on bike ? If so can you please give me an idea how much harder it will be? Also, i am thinking a better design will not be as hard to pedal as a cheaper/ poor design....your thoughts? thx

oh yea...what the latest on your project.... did it work out like you wanted? Have you had a chance to ride the linear limo and compare it to the iowa built ones of yesteryear?

[lawsonuw]

The cheap brushed hub motor I tired was about the same as always riding on a nearly flat tire. I'd expect a brushless hub to be more line an underinflated tire, and a geared hub with freewheel to be nearly imperceptible.

Unfortunately the weight is more of a problem with hub motors. High torque slow speed motors are always heavy. The geared hub motors do improve on the weight, but are usually geared for 15-20mph top speed so still need 2000 or more watts to climb steep hills (i.e. >12% slope). In the end, I'm only willing to tolerate pedaling around about 10lbs of electric system, and I haven't found a hub motor that will climb steep hills at that weight.

The latest on this project is that I've stopped working on it. My initial experiments erred too much towards low weight and broke. Meanwhile, I'm in better shape and don't feel I need assist anymore.

Haven't had a chance to ride the new Liner 3.0. It looks like they've managed to improve on an excellent bike though.

Lawson