Maxis b flat.
They were sold by Cali eBikes when he did hub motors. Kinaye Motorsports now sells the latest versions. Mac will sell direct and there are some sources on ES Facebook if builders ask around. Paul is a good source. the best place to find specific products for builders is still ES dot com, apparently there's some reticence to post there.
Tom,
It seems like one of the ways that people buy stuff is to 1) Google it 2) go to Ebay 3) go to Amazon. Not necessarily in that order. The MAC shows up on Google with EM3ev. The only gripe there is that you have to have it shipped from Asia.
The most accessible hub motor is the Golden. You can get them from Canada, Gary Salo, or Luna, Eric Hicks. I bought a couple of Golden Motors because they were readily available, especially from California.
The Golden has the controller built in, and it is made narrow for disk brake access. It also comes with a dual brake rim. They are heavy. The Magic Pie seems to perform like the MAC on hills, but it weighs 20 pounds. The lighter Smart Pie is OK on hills, but bogs down more quickly.
There are the cheap hubs, Bafang geared, that show up in many assembled bikes from China where the manufacturer is almost an importer of a bike they ordered or had made. These hubs are hard to find just as a DIY motor. Luna has a version, but it's not a very well-developed line for them. I think Grin has one. You can buy them from Chinese vendors, some of whom have been around a while.
Kinaye has been selling the MXUS 3000 watt version for a while, but they are a performance vendor which puts them somewhat apart. Performance costs more. People can certainly find stuff on ES and get advice. The very small vendors probably don't have much of a presence other than ES.
Meanwhile, the vendors of basic (cheap) DD motors on Ebay show auctions with packages and numbers like "45 sold, 15 left". They seem to be generating the volume. You get the same motors on Amazon, more or less. Battery packs are showing up on Amazon.
The two big DIY vendors are definitely putting the emphasis on their factory or in house assembled kit bikes. Lectric has the very well received Smart Motion Line and the lower end Haibike line, plus some bikes they build. Luna has models they build. They say it takes 4 hours to build a bike, in house. This is not a bad deal, paying for that labor, getting a bike that is set up reasonably well. In a video Luna talks about some specific problems with the HD. It's not that simple to go DIY with something like an HD.
In another video Eric talks about being thrown off ES. The politics on ES are pretentious. It's not an outfit most people care about.
The only area of DIY that appeals to me is the basic hub. If I wanted an HD, I would have Luna build it. But the Smart Motion and the Haibike lines have a more refined product. It's tough to say, and the HD gets into the $2's, assembled. I wish there were comparative reviews, Haibike versus a Luna build.
Court - I think that level of build is mostly going to be something you would get in an assembled bike, like what Luna is doing. The price is OK, it's a premium product, so you pay. The bike might last a very long time. Consumers are chasing different things. DIY works at the low end for me. The Mac is fine on my 7-8 % grades, but better with about 1100 watts. They are taking that away with the Cal regs.
Here's the big problem:
