Anyone with ~20" MP Wheels can ya give me some feedback pls?

[MonkeyMagic]

Hey hey

Just finished getting my 20" cast on the road. I changed this from a 16" cast.

No complaints! Both wheels are tops! But of course the 16" would have more torque but it seriously seems like 50%+ more! 16" Casted wheel if you have a bike to fit is fantastic; it is approx. 7-10 less km/h speed than the 20" but seems like so much more pulling power.

I'm thinking I can't have the best of both worlds here.. Unless I get a front 16".... hmmmm

Hey anyone with 20" or even 24" wheels; can you tell me if you can hold the bike still pressing the throttle? Like not wheel spinning or anything but even after adjusting via the USB controller to maximum settings I feel the motor nearly stops going uphill.

Maybe I'll throw some questions out there, if anyone can reply would be greatly appreciated
I'm running a MP 20" cast now with my 48v 12Ah GM battery.

1) Can you hold your bike (not sitting on it) at full throttle? Stopping the wheel, you might have a jolt at first but then does it stop?
2) How is a 20" or even 24" MP wheel going uphills; Interested in spoked and 20" cast if anyone has 1. Does it slow down alot? Mine does by nearly have speed at a 15deg grade.
3) Holding the handlebars gently, then applying throttle quickly does the bike mono/front wheel lift up?

Here's my answers for the 16" Casted
1) No! It will just about push me over if not applying forward force. Starts spinning the wheel instantly, slightly scary in a nice way
2) Barely slows down at all. Just about makes you want to find a bigger hill to climb. About 5% average speed loss uphill, no embarrassment what-so-ever
3) Yes... Could flip the bike easily with rear mounted batteries..


I'm going to put the 16" wheel on the bike I'm running the 20" on and see if there is any major difference. I'll post it up here should anyone be interested. Anywho hope I get some feedback

All I am trying to decide is if I am going to buy a 16" front cast wheel and build some custom gas suspension forks, of which I'm am definitely leaning toward

As you can see I am a bit of a die hard BMX fan [used to race] so being 6'4" tall now I built a custom large single speed - pic below is minus chain and a few other goodies. I'll post full pics up in the gallery when I get some time and good light!

Cheers

[Leslie]

 

Shivers down my spine.

OMG that bike is awesome.  To look at, it almost made me cry.

Looking at the replies here, youre the man Monkey Magic.

Keep up the most excellent work here and please give me the feedback I need..

I am cerfully considering buying a 20" cast in about a few weeks.

Can you give me a nice profile pic (side view) of your bike  so I can see the angles of the different wheel sizes at work.

Thank you.

[MonkeyMagic]

Hey thanks alot mate,

Yes I'm pretty happy with the bike but still have a bit of work to do; electronics wise. It'll be done once parts arrive and I get time so a couple of weeks to end of month I'm tipping. It will be well worth it tho

In terms of your careful consideration, great idea   with the 20" cast what you have to look out for here is your pedal to ground height should you put a smaller wheel on the back of a bike fitted with say a 24" or even larger. I am fortunate enough to have a rear suspension design from a 24" where I am changing the rear spring to a longer one, most likely off a scooter or motorbike. Currently the pedal height is very cornerning at high speed if you don't have your feet on the right angle your feet/pedal can scrape the ground which is not a good tingly feeling!

Changing the rear suspension spring to a longer one will make the mid frame higher but then you still have to modify the cranks to bring the pedals up. Downside again here is of course both comfortability and increase in pedal speed required. I'm modifying the cranks for safety tho, don't care about pedal speed my pie can go faster than I could ever be bothered pedalling  

If you are tall like me I guess you can option to buy a high end BMX in a large size, then bend out the back wheel dropout but I think you would be better off getting a steel frame 24" MTB and modifying it if you are tall to suit like I did. If you are shorter, get a $100 or so steel frame BMX and put big handle bars on it. Possibly even convert it to a six speed if you don't find one with that already.

My near future decision is be boring and get another 20" cast for the front and run them together or try to get my 16" wheel fitted with a safe pedal height as rear, then getting a front 20" cast MP as this would be the strongest, most durable setup.

I would operate the 16/20 setup based on speed via a microcontroller that will run from the MP 5v output.
Based on the speed, say taking off - The motors would function as follows:

0-15Km/h - Front @ 50% throttle, rear @ 100%
15-30Km/h - Front @ 100% throttle, rear @ 50%
~30Km/h+ - Front @ 100%, rear @ 0%

Then work out a 'hill speed' threshold to switch them on and off via software. Plus the idea of having a 7segment LED speedo via the pulse sensor I would need build to monitor speed would be a cool bonus

Anywho enough of that, I still have to finish this one completely first haha
here's some mediocre pics:   [pedal height down the bottom is compared with a standard 20" BMX]

[Leslie]

Thanks for taking the time for the photos.

I do see the crank length being a small but a dangerous problem as you've describe..

Those torque arm (plates) youre doing up seem strong.  Like those maybe you could make up an extention to your rear shock instead of finding a longer or or modify a seat post shock or something.

You are pretty good with your hands it seems.

It would be interesting to see what other ideas you have here.

You wont need to pedal faster them being shorter cranks you will be more capable of pedaling faster with smaller strokes, which smaller cranks are better if your knees are bowing too much when you sit to pedal..  Also better if you have to pedal very fast as youre not having to move you feet around a large circumferance at high RPM.  Meaning your feet move less distance for the same RPM, actually your feet move slower for the same RPM with shorter cranks.

Keep the smaller cranks IMO with your setup. they are better than longer ones and you will feel more resistance on the pedals trying to keep up with the motor as opposed to very little or none at all.
 

Great job BTW.

[MonkeyMagic]

Hey cheers again Les !

The main man replying to my posts Much appreciated

The shorter cranks are a standard 20" BMX height so that's what I was aiming for. Unfortunately the current ride still has MTB crankset and sits lower in the pic due to the longer cranks obviously. I'm no bike expert but I can see by eye the BMX cranks won't fit this MTB, I don't think they do generally anyways. So I'll just tap thread through these cranks, match the bmx height then grind the excess off and paint it. Cheapest way too !

You are right about the pedal speeds, I can't really do anything now anyways because I've misplaced my oversized chain somewhere in my garage haha so I have to pretend to pedal each time cars go past me in case its a cop lol

The main thing is going through a round-a-bout (silly word hey?) and alot of them have a camber change in the road from wear and the pedals can clip the ground. Nothing tragic so far but it is scary and also loud at ~50km/h I need to change this before I have to post a new topic about "no arms" 

Hey also - for others reading this post; Does anyone have a 20" pie they can give me some feedback like the questions in the first post? Still interested to know! Also others who own a 16" cast Pie and any other MP that might want to say what they think of the difference?

Cheers