Voicecoils's 2nd build: Giant DH Team

[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.

 

[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? :wink:

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? :wink:

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.cfm?&DID=7&Product_ID=1762&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? :wink:

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? :wink:

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]

Wow, that's a "Giant" bike! :wink:

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.

 

[voicecoils]

Working on my newly acquired X5. I've got it out of the 26" rim with the flat. My 24" rim arrived too. Now the hard part, finding spokes. Using the Sapim spoke calculator (http://www.sapim.be/index.php?st=spokelength), I get a spoke length of 138mm with a 1-cross pattern. I don't think any other pattern will fit (2-cross) or be strong (radial aka 0-cross).

Sapim make the Leader, a 12ga spoke as small as ~90mm.
DT Swiss make the "Champion" a 13ga spoke as small as 140mm.

 

[PaulM]

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

Used to. I was a Vestas service tech for a while working on V80's. It was extremely interesting to learn about the turbines (fascinating machines) but the work itself was pretty boring. Those turbines in the pic are located, ironically, next to Bruce Power, a nuclear power plant.

Back to the topic however!

 

[Doctorbass]

Hey Voicecoils,

I really think you should consider this way of placing your battery. this allow you a very good handling and lower the center of gravity. Believe me, that help!

and your downhill bike have the exact great room to place the battery. I have this desing and i appreciate it alot!.. people that tried my ebike are impressed bt the handling it have regarding the 130lbs weight it have!

That will also help avoidint exagerated wheely when starting and will give you the right weight sharing on your front tire to help when turning and accelerating at the same time.

Doc

 

[voicecoils]

Hey Voicecoils,

I really think you should consider this way of placing your battery. this allow you a very good handling and lower the center of gravity. Believe me, that help!
Doc

Thanks for your comments. By the way, what was your solution for spokes with the X5 w/ 24" rim? What type of spoke and what cross?

I agree there may be some advantages to you're proposed placement of batteries. Cruisers have low weight while super motos / dirt bikes have the weight more centralised and higher up. So perhaps it depends on the sort of riding your after.

I think with my proposed battery placement the battery weight is a bit high and and towards the back of the bike compared with the KTM pictured above. However, it will be much easier to mount in that position and be more stealth. 8)

If it does feel really bad, I'll look to the option you've draw up. Maybe a super long distance pack 8)

Cheers!

 

[Doctorbass]

Hey Voicecoils,

I really think you should consider this way of placing your battery. this allow you a very good handling and lower the center of gravity. Believe me, that help!
Doc

Thanks for your comments. By the way, what was your solution for spokes with the X5 w/ 24" rim? What type of spoke and what cross?

I agree there may be some advantages to you're proposed placement of batteries. Cruisers have low weight while super motos / dirt bikes have the weight more centralised and higher up. So perhaps it depends on the sort of riding your after.
View attachment 1
I think with my proposed battery placement the battery weight is a bit high and and towards the back of the bike compared with the KTM pictured above. However, it will be much easier to mount in that position and be more stealth. 8)

If it does feel really bad, I'll look to the option you've draw up. Maybe a super long distance pack 8)

Cheers!

I used the 24" rim and spokes that justin sold me. that was heavy 12 gauge spokes. I had a problem cause the nipples did not fit corectly in the holes, so i needed to drill them. Also, the spokes was a bit short! i would have had like 3mm more long spokes. see the pic

 

[voicecoils]

I used the 24" rim and spokes that justin sold me. that was heavy 12 gauge spokes. I had a problem cause the nipples did not fit corectly in the holes, so i needed to drill them. Also, the spokes was a bit short! i would have had like 3mm more long spokes. see the pic

Thanks Doctorbass, do you know what the spoke length was? I have calculated 138mm but perhaps I should add a few mm for dishing.

I am not sure that thick spoke = strong spoke. Spokes almost always fail at the head or nipple, not in the middle. I'm thinking maybe a 13ga/14ga butted spoke may even be suitable.

Can you tell me how many gears are in your cassette and how you went with dropout spacing? Or a link to your build maybe

Cheers! I can't wait to get mine running.

 

[lawsonuw]

How about going with a "half-cross" pattern? (just made this up) If the position of the spokes that I've circled in red were swapped the spokes wouldn't be angled as much. Going with a mixed pattern is another idea I just had. Mix in 6 evenly spaced radial spokes per-side to take road loads, while the remaining 6 pairs of 1-cross spokes transfer the motor's torque. (a 10 radial and 4-pair of 1-cross, or 12 radial and 3-pair of 1-cross might also work)

My 2 electron volts,
Marty

 

[voicecoils]

How about going with a "half-cross" pattern? (just made this up)

Hmm, all radial on one side is done...
http://www.sheldonbrown.com/wheelbuild.html#half-radial

what you've suggested or a half radial would require un-equal spoke lengths, but it is something to think about.

 

[Mathurin]

Well Sheldon did a half radial thing when he had to use an electric trike to get around, on one side all the spokes were leading, and all trailing on the other side.

 

[voicecoils]

Well Sheldon did a half radial thing when he had to use an electric trike to get around, on one side all the spokes were leading, and all trailing on the other side.

Interesting.

I found a 12ga spoke cutter for less then $3k
http://www.biketoolsetc.com/index.cgi?id=433628358683&d=single&c=Tools&sc=Wheel-Building&tc=Threading-Machines&item_id=CU-152

It gets killed after a few hundred spokes at best apparently, but it is less then $100.

I'm still not convinced that a Chinese steel xlyte 12ga spoke will be better then quality 13ga or butted spoke from Sapim or DT Swiss. Then there is the matter of deciding on the lace patter.

I really do need to make some decisions.