Wheels Spoke breakage



I'm on my second rim now. I just got this new rear rim about 2 weeks ago and broke the first two the other day. The spokes always break on the left side, the side the motor is on. I have a Staton Robin Subura friction drive. I was told by the local bike shop larger spokes are not an option, they are not available. Has anyone else had this situation? In 2400 miles on bike and motor, I have broken around 12-15 spokes.
I dont have any broken spokes, at least i dont think i do...

on my last bike, i had to sort of bend the spokes to get the bolts on the sprocket to fit, and when i pulled the sprocket off, the spokes were waaaay bent.

I have heard of others breaking spokes, and i heard something about buying spoke stiffeners?
I had broken and bent more than a few spokes on my GEBE bike before I switched to 12 gauge spokes for my rear wheel. I haven't had a problem since. Knock on wood.
Perhaps the new wheels could use a good once over before mounting it on the bike, that way you can eliminate some potential problems before considering other possibilities that are occuring while riding.
If you buy the wheels from a local shop ask them to check spoke tension before giving them to you.

What kind of wheels are you using?
Do you have to true them often/at all?
Do you check spoke tension throughout your miles?
I presume the spoke pattern is 3 cross (the most common)?
What is the diameter of the spokes right now, and are they butted?

Perhaps there are beefier wheel options than what you are using right now (or in the past).
i have heavy duity 12 guage spokes on both of my bikes and never had a problem with breakage.
I broke my spokes, got them fixed, and broke them again. Im gonna talk to the guys at the bike shop for more durable spokes and tighten my sprocket, if its not tight enough the bolts break the spokes.
Steel 12 gauge are $35-40
Alum 12 gauge maybe $50
GEBE has one with "never need greasing" bearings for around $90 I think.

I use the steel, only problem is a little rust. Then again, I'm a tightwad.
I have to change my opinion of that cheapest 12 gauge, the steel one, because the rust is really ugly, and probably will affect brake shoe somehow.

What brands of 12 gauge do you guys use? I'm thinking the one with the "never needs bearing maintainance" will be the $90 answer, but if anybody uses that mid-priced aluminum one, I'd like to hear if they have had any problems.

Besides the rust, the steel works great, no loose spokes at all.
the steel 12 guage that i use were something like 35 dollors and i havnt had any problems with them.
I'm having trouble wrapping my brain around the forces involved here. How does a friction drive apply enough torque to the rubber tire to break a spoke. I've never owned a bike that would be considered high or even medium quality (aside from my vintage
Rays) and have never broken a spoke. Is it hard braking, going airborne, potholes, or off-roading? I've snapped a rear frame on one of the new Sting-Rays but the thing had over a thousand miles at speeds of up to 38mph., snapped off a brake arm, wore the inner bearing cups out of one of those 4-inch wheels and had the coaster mechanism disintegrate on a Wally World special, but the spokes are fine. Do they break at the rim, at the hub, or in the center? Are the other spokes tight or over tight? Were they true to begin with?