Voicecoils's 2nd build: Giant DH Team

[voicecoils]

Drivetrain: 2nd stage of reduction
I'm liking the idea of #219 chain, normally used in kart racing, and running at speeds up to 15k RPM in a single reduction.

According to this very useful document: http://www.azusaeng.com/Sprockets/AzSDno219.pdf
I can see that in order to fit a sprocket + chain on the rear wheel with the disc brake caliper and disc in place, the largest sprocket I could use would be a 56 tooth one which has a diameter of 5.634" (5.278" at the root of the teeth). The only problem with this is that I don't believe such a sprocket exists as it would be too small for the 6 hole 5 1/4" bolt circle diameter. The smallest I've seen is 63T which won't clear the disc caliper.

The great thing about the 219 chain/sprockets is the high number of teeth for a given diameter. For comparison, the same 56T sprocket for #35 chain is 6.903". I'd have to go down to a 46t #35 chain to make it fit, which I haven't been able to find any of either.

To make either work, I'd be looking at getting a thin flat adapter made which would bolt along with the disc to the hub's 6 hole disc mount. Then from this adapter the sprocket would be bolted and spaced out away from the disc enough for chain clearance. So from the centre outward would be: sprocket, adapter, disc.

Any ideas guys?

[MitchJi]

Hi VC,

Do these help (it sounds like they would make up whatever sprockets you want)?:
http://motorbicycling.com/f3/top-hat-sprocket-adapter-2131.html

OW I have made the "Top Hat" sprocket adapter which is not only super light (a feathery 2.1 ounces) BUT also allows you to use a disc brake if you so choose! All the advantages of the standard version #1 sprocket hub adapter PLUS super light weight and the ability to retain use of the disc brake system if so equipped.(depending on components used may require the
use of custom spacers below and other "tweaks" since space will be at a premium between the disc and sprocket....may limit sprocket size choices in some cases....again all this is dependent on the frame and components used)...

All pieces are made from the same great aerospace grade 7075 T651 aluminum we make our sprockets from....I have been researching Titanium nuts and bolts but will at first make these adapters available for use with your own nuts and bolts.

Another option would be using one of these belt drives (should be quiet):
http://www.bikeengines.com/index.htm

The first and only geared belt drive bicycle assist engine on the market.

[voicecoils]

MitchJi,

The tophat looked appealing at first, however the 9 whole bolt pattern is not compatible with the 6 hole pattern of #219 kart sprockets.

The BikeEngines belt drive is also appealing at first, however I'm not convinced that mounting to spokes is a smart idea, especially if high torque is a design goal for the finished eBike. The site mentions that belt life can be increased by pedaling from a dead stop before pouring on the throttle which suggests to me that they may also be trying to avoid customer issues with wheelsets and the drive ring wear or failure.

Cheers!

[MitchJi]

Hi VC,

MitchJi,

The tophat looked appealing at first, however the 9 whole bolt pattern is not compatible with the 6 hole pattern of #219 kart sprockets.

He makes custom sprockets etc. Maybe he would make what you need.

Cheers![/quote]

I just noticed:

*** Disc brakes (Not recommended):

1. Disk brakes are expensive to maintenance and, because of how they work, put a lot of stress on the spokes w/o motorizing. Braking stress combined with engine torque, puts stress on spokes going and coming.
2. Some disc brakes sit within bike frame, only requiring a washer or nut to space lower strap out, for clearance. Some find the need to grind or file an 1/8" sliver (crescent) from lower strap for brake clearance, others protrude so far beyond the frame of the bike that installation becomes tedious, if not impossible. If possible, we recommend you steer clear of disc brakes.

To check to see if the disk brake would obstruct clearance of Lower Mount Strap - a yardstick is helpful (or something similar).

Place yard stick on top of axle - pivot toward seat then back toward rear of wheel - does any part of the disk brake protrude so far beyond bike frame that it would interfere with the lower strap?

[voicecoils]

MitchJi,

I don't know that he (kingssalesandservice) would be able to retool for a completely different tooth pitch and profile, but I suppose it is possible. I know a place around here which makes custom single speed bike chins 1/2" and 3/16" but again I doubt they'd be interested in the work involved in making the #219 work.

Here's a good site that compares #219 with #35:
http://www.tsracing.com/Techtips/TSchain.html


As for the disc brake comment. I think the excuses for not using one are lame. If you're using a bike with a wide enough tire (large enough contact patch) and want to do any powerful or sustained braking there's no equivalent alternative to hydraulic disc brakes. Look at cars and motorcycles! Hydraulic rim brakes and mechanical disc brakes are both decent and a step above v-brakes/side-pull/canti cable actuated brakes. Instead of him suggesting against them, a better solution to marry the two should be found.

[recumpence]

I'm sorry, but once you use disc brakes, you never go back. I have no clue why he is against them.

Anyway, the only issue I am struggling with on my mountain bike build (have not started it yet) is rear disc brake with a sprocket big enough to achieve the drive ratio I am looking for.

I may have to mod my Avid cailper and make a "Sproder" (rear sprocket/brake rotor). Either that, or put a small custom rotor on the drive jackshaft. Neither option seems apealing to me, though.

So, how much clearance do you have between the tire and seat post at full suspenison travel?

Matt

[dontsendbubbamail]

You might be able to use this spreadsheet to CNC a gear of the size you desire. I found the xls on the web some time ago. Your description sounded like the gear will be going between the disk and the spokes and not between the disk and the dropout. Did I get that correct?

Here is the url to the spreadsheet.
http://www.geocities.com/sidi_steve/NewPix/picView.html

Here is an older copy of the spreadsheet. Hopefully he will fix his link.


Bubba

[lawsonuw]

Anyway, the only issue I am struggling with on my mountain bike build (have not started it yet) is rear disc brake with a sprocket big enough to achieve the drive ratio I am looking for.

I may have to mod my Avid cailper and make a "Sproder" (rear sprocket/brake rotor). Either that, or put a small custom rotor on the drive jackshaft. Neither option seems apealing to me, though.

So, how much clearance do you have between the tire and seat post at full suspenison travel?

Matt

I know a couple battle bot guys who make all the chain sprockets in the bots out of old road signs. Also, according to my dad, one of the old snowcat brands used sprockets that started as a ring of holes and were then cut to the appropriate pitch diameter. Also, looking at bicycle sprockets, tooth shape doesn't look like it matters much roller chain. Anywho, if you get in a pinch I think I could draw up a nice .DXF of a sprocket. Does G-code let you rotate a set of moves around a point and repeat the moves? (I know I can do this on a TRAK 3) Might be able to make a fairly general sprocket cutting G-code program then. One relevant link.

Marty

[MitchJi]

MitchJi,
As for the disc brake comment. I think the excuses for not using one are lame. If you're using a bike with a wide enough tire (large enough contact patch) and want to do any powerful or sustained braking there's no equivalent alternative to hydraulic disc brakes. Look at cars and motorcycles! Hydraulic rim brakes and mechanical disc brakes are both decent and a step above v-brakes/side-pull/canti cable actuated brakes. Instead of him suggesting against them, a better solution to marry the two should be found.

Hi VC,

Just to clarify the post on disc brakes was from the site that had the big belt sprocket that mounted on the spokes (Scroll down):
http://www.bikeengines.com/bikerec.htm

I was not suggesting you ditch the disc brakes. I posted that in support of your decision not to use the big belt drive sprocket.

Even if you can get the reduction you want by going directly from a small sprocket on the motor to a large sprocket on the rear it might be too noisy to be satisfactory. Using Matt's unit with the first stage belt drive to reduce the speed of the chain will probably be much quieter.

[voicecoils]

I'm sorry, but once you use disc brakes, you never go back. I have no clue why he is against them.

Anyway, the only issue I am struggling with on my mountain bike build (have not started it yet) is rear disc brake with a sprocket big enough to achieve the drive ratio I am looking for.

I may have to mod my Avid cailper and make a "Sproder" (rear sprocket/brake rotor). Either that, or put a small custom rotor on the drive jackshaft. Neither option seems apealing to me, though.

So, how much clearance do you have between the tire and seat post at full suspenison travel?

Matt

Everyone,

I'm very near the end of my semester at Uni and am extremely preoccupied trying to get all my end of session assignments and presentations organised. Then I'll have a few days off before final exams begin. In short I'm trying to minimise the time I spend on ebike planning and building for the next month but will then have 3 months off for the summer break. Even so, I can't keep ebike thoughts out of my head! I may check in and see what you guys are up to every once in a while till then.

I'll try to catch up with the other posts later tonight. Thanks for everyone checking in and offering suggestions.

Matt,

The brake/sprocket combined "sproder" is something I've thought about and have seen before. The issue I see is that disc brakes are happy when dry and chain drives are happy when lubricated. The combo is probably not a great compromise but does yield a cool look on choppers.

The only way I can think of to have a decent sized disc brake and a big rear sprocket (or toothed pulley) would be to have a sprocket with quite a complex shape that bolts first to the 6 hole disc mount then kicks back towards the spokes (like the top hat adapter does) and then comes BACK over the whole disc and caliper. Such a sprocket could be machined out of a giant hunk of aluminum, or made with several "rings" with spacers in between.

I'm guessing no one can visualise what I'm talking about but it is a solution in my mind

Lastly, Matt, do you have a good way to measure clearance at maximum compression of the suspension? I can't get much more then my own body weight in compression with the bike not moving and that only really tells me how much "sag" the bike is set up for. Which would be about 20-35" of the overall travel. I guess I could compare clearance with with and without sag, them measure the difference in shock stroke and try to extrapolate out to full travel. But that would assume linear wheel travel and linear behaviour of the shock compression throughout the full travel. Might be a poor approximation.

I might just make a mock up box from your dimensions, tape it to the bike, set the shock as soft as possible, and go outside with it and bounce around and go wild and see if I can bottom out in such a way that I smash the mock up, then reposition or adjust the shock so that I can't.

[voicecoils]

Just re-read your post Matt, I think the disc on the jackshaft is a good idea in the sense that it could be almost universally used. If you had a disc adaptor plate that bolted to your box, which the caliper bolted to alignment could be perfect and reproducible. A caliper to box mount, and a jackshaft to standard disc adapter would do the trick. User would then add their own disc and caliper.

The drawback is that you only have your rear brake when your chain is intact. If your front brake exploded and then your drive chain slung off you'd be pretty well screwed The other consideration is that you'd really never want to brake and hit the throttle at the same time, though that applies no matter what.

Here was my "monster top hat" idea. The outer blue line represents where the teeth are. The innermost ring (inline with the outermost) is where you'd bolt it to the hub disc mount. The kicked in part would be where your head would go, if it was a hat. In this case, it's where the brake rotor and caliper would sit.

monster_tophat.jpg (40.42 KiB) Viewed 2569 times

[voicecoils]

You might be able to use this spreadsheet to CNC a gear of the size you desire. I found the xls on the web some time ago. Your description sounded like the gear will be going between the disk and the spokes and not between the disk and the dropout. Did I get that correct?

Thanks for the attachment. I must admit I'm lost on much of the spreadsheets terminology. I'll have to study the "cheat sheet" tab later.

And yes, from the hub, you'd have: spokes, sprocket, disc, frame dropout. The disc hole mounts on the hub sit a fair way away from the spokes, so there's actually room to mount closer to the spokes, with the right "top hat" shaped adapter.

[voicecoils]

lawsonuw:

Anywho, if you get in a pinch I think I could draw up a nice .DXF of a sprocket.

Cool, I'll let you know if I get to that point . A cad drawing of a small #219 sprocket would be sweet.

I've just remeasured the spacing with my digital caliper. My rotor is a standard 8"/203mm rotor. The caliper sits 26.5 mm from the outside edge of the disc inwards towards the hub. So that gives a maximum sprocket diameter of 150mm (which would just brush the bottom of the brake caliper).

A 56t #219 sprocket would be 143.1mm. Adding a bit for chain height, I reckon thats actually TOO tight. You'd probably want 5mm clearance between the top of the sprocket (top of the teeth) and the caliper. A 54t (dia = 5.438" = ~138 mm) or 55t (dia = 5.536" = 140.61 mm) would be a safer bet.

[rguy56]

voicoils,

ok, for cars and bikes it's true, but if you could find a way to replicate airbrakes...

[voicecoils]

voicoils,

ok, for cars and bikes it's true, but if you could find a way to replicate airbrakes...

people keep gettin' my pseudonym wrong. Many are not familiar with the parts of speaker drivers I guess. Anyways, air brakes would be a more powerful solution though completely impractical on a bike IMO.

[recumpence]

The primary problem with a jackshaft brake would be the added drag. Lets say you have a 3 to 1 ratio i nthe final chain drive, now the rotor and jackshaft would spin at 3 times the wheel speed. That is good in one sence because you can use a far smaller rotor (maybe a 3 inch rotor) with good braking. But, the drag while pedalling would be a neusance. The jackshaft bearings alone would cause enough drag to feel while pedalling. That is the reason I never made a jsackshaft disc brake on my recumbent.

It is a possibility, though.

Hmm, maybe I should have some 10 or 11 inch rotors custom made?

Matt

[voicecoils]

The primary problem with a jackshaft brake would be the added drag. Lets say you have a 3 to 1 ratio i nthe final chain drive, now the rotor and jackshaft would spin at 3 times the wheel speed. That is good in one sence because you can use a far smaller rotor (maybe a 3 inch rotor) with good braking. But, the drag while pedalling would be a neusance. The jackshaft bearings alone would cause enough drag to feel while pedalling. That is the reason I never made a jsackshaft disc brake on my recumbent.

It is a possibility, though.

Hmm, maybe I should have some 10 or 11 inch rotors custom made?

Matt

Doh! A rotor on the jackshaft would necessitate NOT using a one way needle bearing (like a conventional bike freewheel), I neglected to think about that. What about getting tricky and having an clutch that engages from the brake lever which has two positions: one way freewheel (disengaged) or "fixed gear" (engaged). I'm not a mechanical engineer so I have no idea if such a design exists, but it must be technically possible. That would eliminate drag, allow the motor to freewheel or drive the rear wheel, and allow the disc brake to function with the clutch in the "fixed gear" position.

On the small disc rotor, heat dissipation could be an issue.

A monster rotor would work, though would require a matching large caliper adaptor to the frame. A Buell type "inverted disc" could be fun too but then you just start getting a bit crazy.

A rear belt drive could potentially fit over a disc and caliper:

http://www.tsracing.com/store/showdetl. ... 2&CATID=12

I don't know what number of teeth pulley would be required to make it around standard 160mm and 203mm disc rotors + caliper. What are the issues with running a belt as the final stage?

[recumpence]

Of course the oneway could be put in the belt drive pulley on the other side of the jackshaft. There would still be some drag, though.

Matt

[voicecoils]

http://endless-sphere.com/forums/viewtopic.php?f=7&t=7043

An 11kg monster has landed!

[Ben]

36V or 72V? You'd have to go 72 wouldn't you?

I think the 5304s are about 1km/h per (nominal) volt in a 26", so probably around 33 or 65km/h in a 24".

[voicecoils]

36V or 72V? You'd have to go 72 wouldn't you?

I think the 5304s are about 1km/h per (nominal) volt in a 26", so probably around 33 or 65km/h in a 24".

72v of course

My bigger concern is how I'll carry it out of my apartment! I've got 5 sets of stairs to climb up out of to reach the outside world. Lugging ~40-45kg will be interesting in the narrow stairwell My 20kg red bike + 10kg backpack is already quite an effort. I'll be dreaming of having my own garage (then I could get some kayaks too!)

[recumpence]

[quote="voicecoils I've got 5 sets of stairs to climb up out of to reach the outside world. Lugging ~40-45kg will be interesting in the narrow stairwell My 20kg red bike + 10kg backpack is already quite an effort. I'll be dreaming of having my own garage (then I could get some kayaks too!)[/quote]

Wow, that's a "Giant" bike!

Matt

[voicecoils]

.

If time and money permits, I'd like to get both the 5034 and an RC setup going on the bike (though probably not at the same time !!!)

If a 2-4kg RC setup can match the performance of the 11kg 5034, I think there will be some serious interest in the RC route

Have you seen the latest on my Red bike? I don't suppose your in the mood for cutting up some 28t 20 pitch carbon/kevlar gears?

[PaulM]

A Buell type "inverted disc" could be fun too but then you just start getting a bit crazy.

Now you're talking!! Brake disc on the inside, sprocket teeth on the outside!! Buell mounts it to the rim though, that would be one huge brake disc, and sprocket!! Not too mention vulnerable to damage. If one of those 5 spoke (or whatever) carbon wheels was used, this assembly could be mounted to the spokes.

[voicecoils]

A Buell type "inverted disc" could be fun too but then you just start getting a bit crazy.

Now you're talking!! Brake disc on the inside, sprocket teeth on the outside!! Buell mounts it to the rim though, that would be one huge brake disc, and sprocket!! Not too mention vulnerable to damage. If one of those 5 spoke (or whatever) carbon wheels was used, this assembly could be mounted to the spokes.

Ha, carbon wheels on a MTB. A custom carbon wheel could be made tough enough but none of the current ones...

I like your avatar pic, do you work in the wind farm industry?

A buell style brake or sprocket/disc combined would both be cool, but really a simple bolt on solution where both run side by side should be doable.