momus3 said:
Motorcycles have hundreds of horsepower (lord only know how much power the Super Bikes put out), so a chain will take more power than you will ever put through it w/ an electric motor. You'll want to go to motorcycle type rims, spokes, gears etc if you are gonna put a ton of power through a bicycle, which is probably a sub optimal idea in the first place. Automotive engine belts are specific to their application. They don't deliver horsepower to the road, they just spin camshafts.
I was planning on using some motorcycle/coped parts already. I'm unsure if I'll stick to a bike frame or a moped frame, but that's more just based on what I find. Good to know that chains are tougher than I thought.
As for the "Just spin camshafts"- No, no no no. That belt takes the torque and vibrations of the engine and in turning the cams is working against compression in the cylinders and spring tension to keep timing for 100,000+ miles. They absolutely need to take torque, though it might not be as much as your typical gearbox.
flat tire said:
OK show us your calculations where you prove that even a bicycle chain will break under your application and I will show you that you are WRONG.
Seriously go on show me the numbers.
Pump the brakes Don Garlitz, I'm looking for advice and ideas.
John in CR said:
You're focus is on the wrong thing. The weak point will be the IGH regardless of whether you run a belt or a chain.
amberwolf said:
CONSIDERABLE SHOUTING said:
EDIT: Forgot to add, I'll use an IGH with this idea so the belt will have no derailleur thingamathing
Realistically, if a singlespeed chain is unable to handle the torque, the IGH is unlikely to either.
An IGH will have some component in it that will shear or break at torque below that which would destroy the gears, etc., like a shear pin. So...you can probably repair it once it breaks, but it'll require some disassembly. The torque limit of the IGH you're using should be published by it's manufacturer, for that model/year/brand, so you can know what not to exceed.
But if you are exceeding it....
But if I exceed it, that internal drum brake is suddenly well ventilated
I've done a little research on the IGH that came with that used bulk order- it's a little smaller than the SX-RK3 that Karl on the Electric Bike blog ran some 3000w through here:
https://electricbike-blog.com/2016/01/16/sx-rk3-sturmey-archers-3-speed-igh-for-fatties-its-got-the-power-dum-dum-da-da-dum/
... and he claims other people have been running more through them; he's built a ton of stuff and clearly runs crap through the wringer, so I feel like his opinion is sound. I also know from racing that it's shock and heat that kills transmissions, not the torque itself; essentially, as long as I don't shift under load (granny-shift) it shouldn't blow. Finally, I got the thing for $~25, I've wasted more dosh on bad dates
Sturmey-Archer lists no torque specs, sadly: http://www.sturmey-archer.com/en/products/detail/rx-rd3
DogDipstick said:
larsb said:
Question on belt/chain is not which one can take your torque. Either one, properly sized, will work.
...(excellent info, thank you)...
As for the harleys using belts, i think this is due to the massive load peaks and vibrations of the large v-twin engines. In this application belts are probably superior as they have some damping.
In my use, street commuting, i find the belt to be superior but the initial cost and design difficulties has to be overcome. I just switched to chain drive again to play with the gear ratios but likely i’ll go back to belt when i know what ratio i want.
That's pretty much the reason I was looking at a belt- of course, that assumes I'd also learn how to deal with the tension on the frame and wouldn't have to modify it heavily to fit a junkyarded timing chain setup. I can weld no problem, but my time is money! Thanks for the info you two, that was easy for me to understand.
As for Harleys that is correct. V-twins shake
horribly and the belt is needed to absorb the shock, otherwise it'd be transmitted to the rear tire. A friend of mine was given a 76' Sportster for free and we had to loctite every bolt- they all will back out from engine vibration if you don't.
Balmorhea said:
By the time I see them, they're not any of the above. Based on feedback from disappointed owners, it seems that an unlubricated chain and an unlubricated belt last about the same amount of time-- but only one of the two can have its life extended with lubrication.
Yes, if you go to a toothed belt 40mm wide, you can beat the expectations I've developed for these things. But a belt that fits in the same space as a bike chain, is going to dramatically underperform a bike chain.
I have never heard of lubing any belt- let alone an automotive belt like this idea- outside of using a small amount of grease to put moisture back into the rubber, and that's mostly due to UV rads drying it out or to limp something along.
What i'm collecting is that, while chain and gear setups will require replacement eventually they are also FAR cheaper to use and don't require tension like a proper belt setup; the amount of work to make junkyarding something like this together will likely make it just not worth it. Good to know.