Need input on my next build..........

Hey Guys,

I am currently collecting parts for my second build. This is not my mountain bike. That will be done as well. However, first, I want to build a bike that is more "From Scratch" as a real performance machine. To that end, I have decided on a few criteria;

#1 It will be a 20 inch wheel BMX style bike. I want a long frame (long by BMX standards) with a euro bottom bracket for FW cranks. I have always loved this size bike and have always wanted the ultimate "Urban Assault" BMX bike and this would be it!

#2 Disc brakes front and rear.

#3 Chromoly frame for ease of welding and durability.

#4 Multi speed hub.

#5 Four to five KW of power.

Now, I will probably start with either a trials frame (long with euro BB) or a similar cromoly BMX frame and mod it to my liking. I already have the cranks and will be ordering the BB soon. I really need to know the most durable internal geared rear hub. I have heard there are very durable hubs and weak hubs. I want a strong multi speed hub that is disc brake compatible and 36 hole. Remember, the wheel will be 20 inches. That will reduce the load on the hub to far lower than a 26 inch wheel would give. So, that helps. Suggestions on a hub? Best place to buy it?

I also want advice on 20 inch rims. I want strength! Also, I will be running 2.25 inch road tires. So, wider rims would be best.

This bike will be built around my drive (in two stage guise). I will either run my Plettenberg on it (with CNC's 40 series motor on my recumbent). Or possibly two of CNC's 40 series motors (that way I can run two ESCs to handle more power). The motor and drive unit will be inside the frame triangle. I am willing to cut and weld the frame as needed. But I really want the drive inside the frame.

The battery will be high C rate lipos (I am very familiar with them). I will probably make up my own pack in the 7 or 8 AH range (48 volt pack).

This bike is meant for hard riding (borderline abusive riding). I want absolute durability! I want strong everything! I will be riding wheelies, taking it down steps, just plain riding HARD. It will be sort of a very light weight stunt motorcycle. It should accellerate HARD, stop hard, and take a beating.

Anyway, let the suggestions begin!

Matt

It would be fun to try a NuVinci hub.



http://aebike.com/page.cfm?PageID=30&action=details&sku=HU0104

$324

The Rohloff hubs are the top of the line, but too expensive for my tastes.

I've got the new Sturmey Archer 8-Speed, but have not been able to test it yet. It was cheap... about $125. (it might break, not sure yet)

Regular deraillers are good if the power is less than two horsepower... above that I don't know.

Sounds like a fun project.

(all that power will be well matched for Urban Assault riding)

Imagine doing a wheelie with a NuVinci where you could gradually increase your gear ratio as you went. You start the wheelie at slow speed and end at really high speed. The smooth shifting would make that possible.

safe said:

It would be fun to try a NuVinci hub.

Click to expand...

Safe,

Why use RC gear and then put on a gearbox that weighs as much as a hub motor?

I'm afraid the NuVinci doesn't shift freely under load, as you imply.

Matt,

Probably the only multispeed hub up to your task is the Rohloff. Otherwise - 3 speeds seem to be a bit more robust than the 8 speeds. You might like to investigate the SRAM Cargo 5 speed.

Cool.

The Rohloff is jus tway too much money for my blood. That hub is nearly my budget for the whole bike. Actually, I only really need 3 speeds anyway. Hmm, what is the best 3 speed hub (strongest)?

Matt

recumpence said:

Hmm, what is the best 3 speed hub (strongest)?
Matt

Click to expand...

I'm not sure. Probably the SRAM.

Miles said:

Why use RC gear and then put on a gearbox that weighs as much as a hub motor?

I'm afraid the NuVinci doesn't shift freely under load, as you imply.

Click to expand...

They are pretty heavy aren't they? Hmmmm, that's a problem.

I've heard they don't shift under load, but in a wheelie there is little load (since you are balanced) and you could gradually increase the gear ratio... at least I would figure you could.

As for three speeds, I really don't know which is the strongest.

safe said:

They are pretty heavy aren't they? Hmmmm, that's a problem.

Click to expand...

Just under 9 pounds, I'm afraid......

Do you really need even 3 gears for the motor, Matt?

Miles said:

recumpence said:

Hmm, what is the best 3 speed hub (strongest)?
Matt

Click to expand...

I'm not sure. Probably the SRAM.

Click to expand...

I have both, but so far only one has gotten a real workout, the Nexus 3 on my Mariner, with the Cyclone 1000W. The 16" Dahon Curve D3 that I'm currently working on to add a Hacker-driven crank setup, has an SRAM 3-speed hub. Both shift smoothly.

I know a guy who builds custome electric chopper-style bikes, using Mars and Etex setups, and he saythe Nexus-3 is all he'll use. I should point out, however, that he uses V-belt drives, to the rear, and that provides a bit of natural slippage, like a clutch. Even still, though , these beasts have crazy power, and he's not had a single problem with the Nexus-3 hub.

Miles said:

Do you really need even 3 gears for the motor, Matt?

Click to expand...

Good point Miles. Actually, this bike will be used in a very specific way at a specific speed most of the time. I think I will go with single speed.

I have a cool idea for the drive setup.

You will love my idea, Miles.

Matt

I think I have the bike layout finalized in my head. :wink:

I cannot wait to order all the goodies to show you guys!

Matt

Give us a clue........ I like guessing

Edit: Ah, I see you already have :wink:

If you want strong rims-ask ypedal-I bought his wide heavy duty 20" rims for my motard project and they fit 3" chopper tires-but I think your 2.25 will fit just fine as well.He got these rims from the zero motorcycle guys before they switched to 24" rims.They are priced cheap as well.

I have to agree about the nuvinci, I did a project earlier in 2008 that used a nuvinci along with the honda gxh50 gasser engine. As soon as you torque the hub it locks the ability to change gears. In order to move the gears it was necessary to back off the throttle. And it was very heavy indeed.

For real breaking performance, use the front hub that Aussie used on the front of his trike that allows for dual disks.

TPA said:

For real breaking performance, use the front hub that Aussie used on the front of his trike that allows for dual disks.

Click to expand...

Yes Matt has already inquired where i picked up the hub hehehe...I would turn one up out of ali in the lathe if i was you with your oober skillz mate, the front hub i use is pretty weighty its steel not aluminum...

I have considered my own hub. I may go that route. For now I am going with a single 203mm rotor in front and a 160mm in the rear. With 20 inch wheels, that should be fine. Plus I am restricting this bike to 25 or 30mph.

I have decided on a frame, rims, spokes, cranks (I already have those), drive layout, ratio, handlebars, stem, and a seat "System". I say seat system because I will be making a rear subframe that will hold the lipo cells, ESC, and other electronics. The frame normally would not have a seat at all. :wink: Is that a good hint, Miles?

Matt

I hate to come in tarty on this, but I have been through many trials on my way to this design. I have to echo many words said here. To be honest, my single drive in this project is E-bike joy.

Hmm, how many hints can you find there?

Matt

Hi Matt,all, Happy new year!!

Matt,

looks like your set already but just thought i'd let you know i have some good quality 20" rims here for you if you want them?
the rims are quality dual wall bmx,32mm wide. they're new bar 10 rides or so but the rims are mint? brand is "gusset" black dog.
Give me a shout if there any good, i have the tyres and slime tubes shown in the picture and also some brand new maxxis holy roller tyres, if they'll help i'll just post you the lot

Cheers,

D

.

Cargo,

Close, here's the frame I think I have settled on.........
http://www.tartybikes.co.uk/product.php?product_id=10626&category_id=36

D,

Are those complete wheels or just the rims? If complete, can I see the rear?

Matt

let me go check whats where, they were old pics.brb.


D

there a bit of a mismatch but heres what i have in 20's.
being as you have to relace the rear anyway you could be set?
there's liner rubbers for the rims and i think slime tubes and tyre liners for both wheels, never had a flat with these yet.
let me know if anything is of use for you :wink:
btw are you planning on having front suspension?single crown fork? this could be nice 8)

cheers,

D

I like your idea of the integrated rear subframe. I got me thinking maybe the bike you are designing could be good at everything if you added a system similar to the Softride



Or maybe something like the Thudbuster



Then you could sit down and enjoy the ride 8) , or stand up when you need to. Maybe even use titanium to take advantage of it's properties of flex.

OK, here is what I have come up with;

Trials frame. Probably the Onza.
Trials 20 inch front/19 inch rear wheels (36 spoke). Extra wide (probably 40mm or wider rear).
Hope 203mm hydraulic front disc brake with 6 piston caliper, 160mm rear.
Echo FW cranks (already have these).
Double right side drive similar to Miles' setup. I will use a double sprocket FW with a large (36 to 40 tooth) sprocket mounted to the inside of the FW for the motor to drive. The existing 17 tooth outside sprocket on the FW will go to the cranks. 40 to 44 tooth sprocket on the crank FW.
Dual stage drive with 20 to 1 reduction with my Plettenberg or maybe CNC's. That should give me 23 to 25mph top speed. With that much power and a low ratio, this thing should have HUGE torque! I may go with a chain primary stage on the drive unit if the belt skips.
I will run 48 volt 7AH, 30C lipo pack. Light and small, but VERY powerful! The pack will weigh under 4 pounds.

I will weld together a chromoly subframe for a seat and a place to store the lipo cells and ESC.

Oh, I will run a tall trials stem and riser trials bars.

This bike will be a cross between a trials bike, freestyle bike, aggressive street machine, and practical/rideable bike (reasonably comfortable).

I think the AUW should come in at about 40 to 41 pounds at the most. I want this bike to be a very good performer with power to spare and easy to flick around.

Matt