"peak power" - Trek 4300 20" Magic Pie build.

What is your front wheel size? If you run same size front and rear you should not have geometry problems. You could also swap to a shorter front fork. If the pedals are too low just keep them level. This isn't rocket surgery nepteonix, its a one time deal for you. Front 20 inch bmx with disc hub is awesome. A kids mtb bike like I modded also works great even stock. Ill pm u my number if u want to talk.
 
Well, it is a bicycle race, so i want to be able to pedal. I have a 26" front wheel and a 20" back wheel, as you can see in earlier pics. The geometry is most definitely screwed up and i had to go to 145mm pedals to not be scraping my pedals on the ground. Double 20" rims would make the pedals excellent kickstands.. :lol:

I think the reality with this frame is that the bottom bracket may be an inch lower than most. I pedal scrape on my other Trek ( same generation, slightly larger frame. ), with a stock fork height and a crank length that is only 5mm taller than what came on it stock.

I am 6ft tall with longer legs, so a BMX setup doesn't work too well.
Folding bikes seem to unstable, tried a bunch of those.
I found two people locally who can fabricate for some $, but they are not too serious about this.
The genesis v2100 bike i own with the farfle swingarm seems to also be a pedal scraper if you go 20" wheels.

Still living in an apartment, but have dreams of owning a house with a garage where i can work with metal, weld and such; put together these awesome custom frames that everyone is making here on the forums.
Until then i am a bit limited on what is possible.
So 26" sounds good, but an extra half inch of raise in the rear should help quite a bit.


Next week i go to Utah to visit salt lake city. There is a KMX dealer out there. I'm taking my big car out there with the lady, in case i fall in love with one, scrap this build, and put a pie on the back.. till then, this build is definitely in flux!!

All i know is that i'm not too happy with the stability/handling of this bike.
 
Also, thanks for the offer auraslip. Real hard to find a 24" with disc brakes. We'll see how things go with the fat rear tire, if i get enough clearance to pull a front 24 off.
 
Building wheels requires one tool: a spoke wrench.

Cutting down pedals and re-tapping them requires a hack saw, a drill, and pedal taps.
JwKFQl.jpg


It seems to me you're hitting a wall that you keep trying to go around but you can't! Eventually you're going to need to get some tools and get your hands dirty.
 
I'd love to get my hands dirty, dude. But i live upstairs in an old victorian below cranky folks. I will probably be a nomadic apartment dweller for some time. Me and the lady are still hunting for the right place to put roots down. We know it is west of California and east of Kansas. That's about as far as we got it nailed down :)

You should see how extensively i've utilized my kitchen. I'm maxed out on what a man can do in an apartment :lol: seriously.. bike parts, lipo, electronics, hardware strewn everywhere. It's like an episode of those TV shows about out hoarders. :lol:

More experimenting needs to be done. But a 26" or 24" rear wheel motor would help greatly, but everyone keeps telling me to forget it.

The idea of running the 5kW golden motor 'car motor' keeps coming to mind. Heavy as hell, but a fitting end to all my power wants/needs, lol. no probs with a 26" wheel and proper geometry.. or cooling when only running it at 3kW constant..
 
Hardware store, drillin', grindin', and angle grinder when the downstairs folk are at work ;)

I surely could put together a wheel. I guess i just don't have the interest to invest the time into learning how.
 
havent got those photos of the 4 computer fan, vented cover pie up yet, but incase it helps, the pie was good for 31NM constant without any ventilation and about 41NM constant with drilled out covers and fans on and all in still air.

so using justins sim for 100kg? it says about 2100w in, and 36kph up a 12% grade, this is the max (continuous) you can climb with a 20" wheel.
 
Toolman, been waiting for your update ;)
I am 240lbs, so that 100kg figure is a little low, lol. But the grade is going to be more like 7-10% continuous..

If you're right, after cooling and all that stuff, then i'm gonna blow this motor, period.

p.s. the golden motor '500w' in justin's simulator is not the magic pie, so what motor did you select?
 
100kg is 220lbs , and i was using justins sim backwards as i knew the motor can do 41NM so it didnt matter what motor i selected, the end result is that you would be well clear of overheating as long as the grade of your climb stays below 12% and even then, you are doing 36kph.

so on a 10% grade you could prolly do 45ish kph forever without overheating it, reckon most 6kg hubs might struggle against that. :wink:

thats without adjusting for altitude though, it would be hard to get my lathe/dyno setup up the top for testing this.
 
Well, the whole rig, 30 pounds of batteries, 240lb rider should be about 150kg.
Will also need a bigger tire.. so i am going to be running more like a 21".
Max speed on 83v nominal ( 22S lipo ) is going to be 32-34mph, which is a bit on the high side :/

I think i need a bigger motor, dudes.

Two 26" pies is appealing, but 32lb of motor is kinda burdensome, lol.
Maybe i'll start selling off all my crap ( including the beloved MAC motor.. weep ), take out a little loan and just get a cromotor.
I think it'll do the job of 25-30mph constant on a 24" wheel.. :)
 
Just realized a cromotor problem.
single speed gear. That means 16t on the rear. I have a 60T front chainring, but that only means for a ~23mph pedaling speed on a 26" wheel.

My ideology of it being a bicycle means you have to be able to pedal. Sorry - i'm fixed on that idea.
This is verging on hilarious.

KMX kart with either the magic pie, or a 5kW golden motor rig continues to look more and more appealing by the day. I have a big aerodynamic advantage with the KMX. Probably enough to prevent overheating.... and the 5kW motor could be much more easily mounted.
 
Whoopi come to bay area and root here so until would see me and bunch of ebikers include Edward Lyen, Eric (green machine) and etc but let me warn you that here living cost is a ridiculous! :D

Sent from my Tbolt smartphone using Endless Sphere app
 
Err.. Whoo. Not Whoopi. ES app won't let me fix this error and save the post.

Sent from my Tbolt smartphone using Endless Sphere app
 
Just called Utah trikes.
They have 60 KMX bikes *in stock*, and 440 other bikes *in stock* at the store.. What the...!!! this place has got to be huge.

Looking at the the Typhoon.
Well, this thread just officially got derailed. :lol:
 
Would be wonderful to be in the bay area, but i ran from CA for a reason ;).. I do dearly miss the west coast. Plenty of eBikers out there. All alone out here 'cept Tom Tom, who hasn't even got a bike together yet lol..
 
neptronix said:
Just realized a cromotor problem.
single speed gear. That means 16t on the rear. I have a 60T front chainring, but that only means for a ~23mph pedaling speed on a 26" wheel.
Click to expand...

Your numbers are off a little. Right now I run a 20.2" tall rear tire and have a 48T front and 16T rear, that lets me pedal comfortably to 16mph. which puts my cadence between 80-90 RPM. After in install my ATS Speed drive I'll be able to comfortably pedal at the same cadence but in high speed mode I'll be at 25MPH (the ATS is very reasonably priced and I should be able to get one for you).

I'm moving to a 52T front and keeping the 16T rear, that's going to let me do 17MPH in low and 27MPH in high.

If you have a 26" wheel and run a 60T front chain ring and a 16T rear you will be doing 26 MPH in low and if you use a speed drive like I'm going to your high will be 43MPH at a cadence of 90RPM. I'm gong to be doing this same mod to my mountain bike most likely. Shifting is accomplished by taking your foot off the pedal and pushing the button on the crank with it. It's pretty slick. I just wish ATS made the 2.5:1 high speed drive, Schlumpf wants $750 for it and that's way to much for me but would allow me really high speed pedaling even on my small tires.

I did find a 15 tooth freewheel that fits a standard BMX without a flip flop at one point which helps a little. It would get you to 27-28MPH.

We can talk tonight about options for what you want to do no matter what motor you want to use. You seem to be all over the place right now. Small wheels are the key to climbing steep hills without burning up a hub motor and controller.
 
neptronix said:
Will talk to you tonight.

http://www.sheldonbrown.com/gears/

I used the trusty ol' sheldon brown calculator at 80rpm to get my 26mph figure.
Click to expand...

Yeah, I did end up the same as you. Sucks not being able to run an 11th rear but there just isn't any room to do it. I enjoy pedaling along with my bike most of the time, but that's also why I have 2 bikes. Realistically my fast bike just isn't good to pedal as it causes more stability issues from a stop than it's worth. Once I'm moving and up to a slow speed like just cruising on a bike path it's worth it. Once the ATS speed drive is in I'll be a lot better off because I do a lot of bike path riding at 15-25mph.
 
Toolman2's calculations were based on 220lb though, total weight will be above 300lbs, and i designed this bike for a much higher speed, so i'm a bit nervous about the whole thing honestly.

I feel like i am going to ride the margin of error way too damn close. Maybe i will run 16S on it for a top speed of maybe 25mph, then pedal like a manimal to try to keep it at that speed. A taller tire may add a MPH or two on top..

ZombieSS gave me an idea to use a full suspension bike with a longer shock, which gives me a slightly smaller wheelbase, but would provide a lot of raise up in the rear of the bike. Then i can run a smaller wheel up front. It would handle many times better, i am sure.

I must say i am facepalming myself for not thinking about that.

K2_attackframe.jpg


Picked this up today for $60 and i'm thinking it's a better candidate for a serious swingarm upgrade. It's got room for the falconEV bag. It's got room for the controller on the top tube ( nice and flat! )... I am going to take the swingarm over to a few local folks who fabricate stuff and see if i can motivate them to help out.
 
your picture isn't working obiviously wrong link or misspell the URL link?
 
duh... fixed..
 
With that shock mounting I don't think your a candidate for using a longer shock. You really need something where the shock mounts behind the seat tube like a NEXT frame or something like that. On that frame you are just going to cause the swing arm to hit the seat tube.

Something with dual disc brakes is ideal because then you just upgrade the brakes or even keep the stockers since they will work better on 20" front wheel built with a disc brake. Then buy a longer shock. Looks on craigslist for a Next bike or something with dual discs and the proper shock mount, then get to it. I always prefer to have a rear brake and not count on regen because regen gets controllers hot when you use it a lot. Your only custom fab work is having a bike shop build the front 20" wheel with a disc brake from a MTB hub which you can probably scavange from the craigslist bike. Since the bike is already setup for 26" wheel it will be easier to adjust your seat height for pedaling and the frame will be longer than a kids bike like I started with.
 
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