Belt drive Sprockets on the Cheap!

[Hillhater]

Most kart racers only ever use 3 of the 6 mounting bolts ( and thats with 20-25kw motors) so you can radically simplify that adaptor design, especially with a wide belt pulley which is much more rigid than a 4mm thick chain sprocket.
Some typical kart sprocket hubs..

 

[Miles]

Ok.

48 grams

 

[Hillhater]

Very nice !
now, we just need Pfeifer to make the matching sprocket in composite and we are set ! 8) :wink:

 

[Miles]

With a 65t pulley, mounted in the maximum offset position.

Needs some lightening holes in the pulley..

 

[bandaro]

Needs some lightening holes in the pulley..

Yeah, all that effort into the rest to make it as lightweight as possible then you go and bolt it to a chunky steel belt sprocket... geez...

say, what size are the teeth on a htd 5mm belt? possible to cut with a 3mm router bit or are they going to be too small? if a 3mm router bit can do it, wanna upload a dxf of a 60t 5mm htd sprocket? pretty please someone?

 

[Miles]

Yeah, all that effort into the rest to make it as lightweight as possible then you go and bolt it to a chunky steel belt sprocket... geez...

The pulleys are 8M HTD and are made from aluminium alloy :wink:

 

[bandaro]

so as a metals design student, i would be interested to know what needed to be done for corrosion of that.

I am assuming that the centre part will need to be a steel so as not to break? is there going to be a need to keep the two isolated or will they not have that sort of lifespan? or am I being paranoid and they will just bolt together?

 

[Miles]

No, the adaptor will be aluminium, too. Otherwise, one could use an isolating washer, I guess.....

 

[katou]

Let me see if I understand:

Pfeiffer Ind. sells nifty belt sprockets in sizes we can use for a belt drive on our bikes.

In order to use them, we need an adaptor that will fit the bike and the sprocket, which is 6 holes, 6mm each, on Bolt Circle Diameter (BCD) 5.25"

The adapter attaches to the disc brake mounts on the left side of the wheel.

Do I have this right?

Katou

ps. why are the sprockets cut in half?

 

[Miles]

Let me see if I understand:

Pfeiffer Ind. sells nifty belt sprockets in sizes we can use for a belt drive on our bikes.

In order to use them, we need an adaptor that will fit the bike and the sprocket, which is 6 holes, 6mm each, on Bolt Circle Diameter (BCD) 5.25"

The adapter attaches to the disc brake mounts on the left side of the wheel.

Do I have this right?

ps. why are the sprockets cut in half?

Yes, you got it.

The split pulleys are for quick change-over, on Go-Karts. Unitary would be better for us (well, me...).

The 3 arm adaptor wouldn't work with a split pulley.

 

[katou]

The King Top Hat adapter is a proprietary BCD (damn them)

What BCD does Recumpence' adapters have?

It is certainly interesting that an adapter that would fit these belt drive sprockets would also open up the Extron option, as well as the full range of other Kart sprockets.

Could the adapter be made without a lathe or mill? I've seen some pretty awesome work around here just using standard tools. How necessary is that offset? It makes building the thing much more difficult.

Could it be made from flat aluminum plate? I plan to use this system for my coming RC build, so I'm invested.

Katou

 

[Miles]

What BCD does Recumpence' adapters have?

130mm. 5 hole/arm. [I did the initial model ]

 

[Miles]

Could the adapter be made without a lathe or mill? I've seen some pretty awesome work around here just using standard tools. How necessary is that offset? It makes building the thing much more difficult.

Could it be made from flat aluminum plate?

You'll probably need an offset. No real need for anything to be circular, though..

 

[Miles]

For 40mm non-split pulleys, see page 9 of the attached pdf.

 

[Wheazel]

Is the HTD the most common and "proven" ebike toothprofile?
I have seen it advertised as a high power profile, and slightly noisier. Is this accurate?

 

[Miles]

HTD stands for High Torque Drive.

Gates PowerGrip Gt has a similar pulley profile to HTD for 5M and an identical one for 8M (AFAIK). PowerGrip GT3 has the greatest capacity without moving to the Polyurethane PolyChain type belts.

 

[Miles]

6 arm version WIP.

65 grams....

 

[Thud]

I Like that one Miles....keeps the 2 pc pullys in play.
I speculate the 25mm width is going to be an issue with many tire widths & chainstay combo's.

 

[damonjackson_spl]

GO KART 01014 Pulley, 80T 8m 40m Aluminum $78.05

I keep coming back to Pulley Stock...

pulley stock in 8mm pitch HDT 80T comes 6" long, so you can get 6 pulleys at 25mm width would be $54.00 per unit, and 10 pulleys at 15mm width $32.40, just need to cut the stock down...

 

[Hillhater]

I Lile that one Miles....keeps the 2 pc pullys in play. .

Is there any benifit in using the 2 piece pulley ?
It just makes the assembly weaker 1
PS: I suspect you could easily adapt one of the kart sprocket hubs to the disc mount.
They can be had with a 25, 30, or 40mm bore and would just need the mount holes drilled and tapped ( + clamp boss removed!)

 

[Thud]

Benifits?
the only thing that comes to mind is availability.
As to srtength, how strong does it need to be?
Seems to work for some serious kart racing applicaitions shold be more than enough for any bicycle application.

 

[Miles]

I keep coming back to Pulley Stock...

... just need to cut the stock down...

There's a fair bit of machining to do on quite large diameters. But, if you're volunteering...

 

[damonjackson_spl]

I keep coming back to Pulley Stock...

... just need to cut the stock down...

There's a fair bit of machining to do on quite large diameters. But, if you're volunteering...

haha it wont be me personally, will sent it to my brothers marine shop and get an apprentice to do it for a 6 pack of cascade draught!!

I just need 10 pulleys :|

 

[Hillhater]

Benifits?
the only thing that comes to mind is availability.
As to srtength, how strong does it need to be?
Seems to work for some serious kart racing applications should be more than enough for any bicycle application.

The split pulley ( and chain sprockets) are usually only an "option" (+cost) over the standard unitary components.
Karters (4 stroke specifically) have to use them because their drive is located between axle mounts.
The split sprockets need a flat continuous mounting face to ensure alignment and rigidity. IE , back to Miles 150gm design
Unless there is a real benefit for you, i would go with the unitary pulley.

 

[boostjuice]

I speculate the 25mm width is going to be an issue with many tire widths & chainstay combo's.

I was thinking about that and I predict that if a large enough pulley diameter is chosen and the cavity side of the pulley is facing outwards from the wheel, you could partially run your disc brake rotor and caliper inside the pulley cavity, saving valuable axial space. You wont be able to fit an 8 or 7inch rotor combo in a 90T pulley, but a 6inch rotor combo would fit from my quick measurements.