Great thread. I have a Performer dual suspended 26" recumbent to build as an electric commuter and am weighing the options of a Clyte 3540 rear vs mid drive. I have an idler midway back already so this would seem a good place to mount a motor. The rear suspension would work better without the added mass of a hub motor and using the gearing will be more efficient on the hills. My main concern would be chain wear on a rear shifting 9 speed and even at 5:1 in the front, I would have to run the motor at 500 rpm if I want to pedal. Can Goldenmotor wind the 800 Watt motor for efficiency at 500 rpm?
I will also add a fairing. Something like this.
The BLDC Trike Motor BLT-800 spins at approximately 1100 RPM at 41.666V at it's designed "efficiency speed" (to get the RPM down you will need some form of single stage reduction to get close to your target RPM) and depending on your target speed, you're going to need to use between a 4 to 7 : 1 reduction.
Personally I gear mine for slower more bicycle appropriate speeds since I plan on using it on bicycle paths and lanes most of the time, and just need the power for maximum distance and torque (hill climbing) when I am unable to pedal as much.
One thing also to note, the faster the motor RPM, generally the better the efficiency, and greater torque potential, thus the "volt up, gear down" adage. The higher volts also allow for less amps being used which generally means less heat for the same wattage.
Any time you're going to introduce motor stress on a bicycle drive-train and especially something that is going to have the bike traveling faster than it would be by pedaling, you are going into unexplored territory since the bicycle components were never designed for this, and typically the higher end "weight weenie" ultra light bicycle components aren't going to be ideal for this, the middle of the road and specifically designed "touring" or cargo bike rated equipment is what you want.
I use the NuVinci rear hub CVPT transmissions for this reason. It's designed to take a lot more torque and has been proven to take up to 9 HP and around 50 Ft/Lbs continuous load (Model N171B, the newer N360 hasn't seen such widespread use yet to confirm) with out any wear or damage, if you exceed the 9 HP for example, it just starts to slip internally acting as a "clutch" and even those with gas powered bicycles have done this with out causing a failure, just discoloring of the internal fluid with this extreme use, and no damage.
I have also talked with local shops in Portland, OR and have yet to find a single shop who has had to send off one of these hubs for service internally, any service or repair has always been related to the cabling going to the hub and usually damage from falling on the shift rod on the right side that can be easily protected from falling/crash damage. Simply put, I use them because they are the most proven and reliable rear hubs/transmission available. Typical bicycle derailleurs and cassettes are designed with weight and efficiency as primary concerns, not strength, and they aren't designed to work with the kind of power this motor or any other that will put 1000 Watts+ continuous power, and will wear out bicycle chains as well.
First off, what kind of speeds are you planing on going?
Any weight you will have on the bike for cargo, or will this strictly be a performance machine?
I have a really nasty long steep hill where I live (on top of course, so any trip longer than 2 -3 miles means going down then back up it) and most of the time if I can't get things locally, it means climbing it to go to town.
This motor isn't pulling as hard as I would like for a cargo bike's purpose, unless you have a lot of your own leg power to contribute on the hills.
It will climb them under protest on it's own, but on the really steep parts you will have to watch the heat and give it a rest after about 1 mile of steady 5%+ grade climbs running at about 1100 Watts (44V or 12S Turnigy 25-50c Nano Tech LiPo at around 25 Amps), and it keeps this efficiency pretty steady, but it has less torque than my Amped Bikes 9 x 7 DD hub motor.
I'm hopefully going to be able to test this motor soon with some active cooling (copper tube "jacket" around motor with a PC liquid cooling system and push the volts closer to 60 - 72V) but this won't happen sooner than my finishing my current Cruiser E-Bike project which is using the same motor.
I'm going to have to re-gear and have some sprockets made to accomplish this.
One thing I would recommend avoiding is the long run of #25 chain as you see in this build, it's just too long a run for that small of chain.
I'm going to be testing #35 chain next, it's commonly used in industrial applications (manufacturing) and the chain can be bought at most local hardware stores in a pinch (I would use higher grade chain than you will find at the HW store) and my local McGuire Bearing sells the sprockets/cogs very reasonably priced.
I think it will do better handling the loads of the motor.
I hesitate to advise using the bicycle gearing with any motor because it's difficult to say how well it will work unless you were to go with a fairly low powered system, how well it will shift and wear using the power through the bicycle drive-train, and usually freewheels are the weakest link.
I'm not sure which model of Performance Recumbent you are using?
It's worth noting that generally anything that is designed to be extra lightweight and is optimal for bicycle applications will not always be best in an E-Bike.
If you're using a light weight Aluminum frame, be extra cautious, the extra stresses will be hardest on your drop-outs and you will have to beef them up even with a steel frame most cases with some torque plates of significantly hardened steel, or better yet, something like the clamping drop-outs that John in CR uses (This applies to mid-drives too since you will still be putting considerable torque to the rear wheel, see the damaged axle flats on my NuVinci in this post for reference, and the suspension makes things more difficult with a mid-drive since you now have chain growth issues to contend with.
I would lean towards a mid-drive that is mounted on the bottom side of your rear swing arm just to the rear of the pivot to minimize unsprung weight, and hopefully that is a Steel or Titanium frame rather than aluminum?
If it is Aluminum, it's not impossible, just remember Aluminum will tend to crack where the other two will bend first and give a little warning before failure, and just try to keep things as simple as possible.
If you do put the mid-drive under the seat, look into a chain guide/tensioner like Down Hill bikes use to account for chain growth, it will probably need to be mounted very near the pivot or on the rear swing arm.
Also note that putting power to the motor at the mid-point will tend to compress the rear suspension under throttle.
From looking at their site, it would seem you have a Goal-X?