Here are a few pictures of the newest project/product.
The pictures do not do it justice.
This is (obviously) a final stage belt drive. It is very unique, however. I have done a lot of research into this and found the best solution I could. Here is what the drive consists of;
---The pitch is 8mm.
---The tooth profile is Polychain, not the typical HTD.
---The belt style is Contitech Syncrochain Kevlar cord.
---The freewheel up front is a Sprague oneway style clutch rather than a standard clicking freewheel.
---Ratio is 3.07 to 1 (26 tooth front, 80 tooth rear).
My reasons for using these particular components is multifaceted;
First, even at 8mm pitch, 15mm width, a HTD belt would be near its limit with a 3220 motor. This belt and tooth profile is WILDLY over speced. This particular belt in a 40mm width is used as a jackshaft to track belt on 400hp supercharged snowmobiles! So, this application is child's-play for it.
Second, the Sprague clutch is silent and does not have any backlash like a normal freewheel. This allows for silent freewheeling and silent engagement.
As for the specifics of running a belt to the rear wheel, these are numerous also;
#1 (this may seem a bit petty to some here) it keeps everything clean. I am sick of chain lube all over the frame ALL THE TIME! It is a pain to constantly clean that crap.
#2 Longevity. The belt should last forever in this application.
#3 No service. The belt will never need retensioning. It will not stretch like a chain.
#4 Efficiency. It is shocking how little drag there is, even if I run the belt really tight.
#5 Quiet. ------ This is, probably, the single coolest aspect of the whole project. The drive is almost completely silent. When running it with the wheel off the ground, all that is heard is wind noise from the spokes and tire tread and the motor whine (which is very quiet). I had no clue how much noise the chain made before running this! The wind noise completely drowns out the electric drive sound. It is almost irritating to not hear much of anything while riding. I like it!
#6 Stealth. This setup (once the rear pulley is anodized black) will be less visually obtrusive than a chain. Though I admit it is so different, it does catch attention in certain respects.
#7 weight. This is a first prototype. So, final weight is yet to be determined. However, I can tell you the rear pulley weighs pretty much the same amount as the sprocket did, but the belt weighs almost nothing! The front freewheel is a tiny bit heavier than the stock freewheel. However, that weight is in a small diameter located in the center of the frame. So, this system has far less rotating mass and far less mass at the outer extremity of the vehicle. This reduces the moment of inertia and improves handling a touch.
#8 No more thrown chains! I have gotten sick of throwing chains. Even with chain guides, for whatever reason, I throw a couple chains a year. No more with this setup! The belt will not run off the pulley. Belt tracking is fantastic on these style belts and pulleys.
Final price is yet to be determined. However, I can tell you it will not be cheap. It looks like the two pulleys and belt will be around $400 (maybe a tiny bit less depending on a few factors). However, my thoughts on this is, that is only about twice the cost of the White Industries freewheel, chain, chainring, chainring adaptor, and bolts we are using now. So, for a new setup, this only adds a couple hundred dollars. Not too bad if you are building a high-end bike.
Lastly, a belt cannot be taken apart like a chain. So, the center to center distance of each setup mush be taken into consideration and a belt obtained for each. Also, this setup eliminates the ability to run the belt around the dropouts on some bikes because, again, you cannot separate the belt to go through a frame. So, some setups cannot use this. Pretty much all trikes and most bike setups can work, however, depending on how the system is layed out.
I think that is it for now!
Matt