My Build Plan: Advice?

[alex220]

I am new to the ebike world! I would like to put together a bike for a fun project and to increase my knowledge of electric motors/batteries ect.

I've spent the last week on here researching as much as I can....

I would like:
around 30mph top speed
Range: Not very important to me, no commute, just fun to ride around locally.
Stealthy
Close to plug and play since i'm a novice
Cost: we will see

Here is what I have on my want list so far:

Bike: Trek 4300 or similar (hardtail). I know this has been used a few times.
Or a suitable FS MTB, recommendations welcome.
Motor: MAC 8t
Batteries: Cell man 50v Samsung triangle pack 18.5 ah or 12.3 ah....
Controller: 12 Fet 3077 40a
Thumb throttle
7sp DNP 11T Freewheel
Grin Tech rear torque arm
Cycle analyst v2.3 or 3

So i want to use a triangle pack, if i get the 12.3 ah, I can only run 25-30 amps correct?
How much of a top speed diff with the 12.3 vs the 18.5?


Also, any FS bikes you can recommend that a triangle pack can fit?


Thanks so much everyone!

 

[footloose]

Kit from EM3ev is pretty much plug and play moron-proof setup (I did it, so must be.) :wink:
I have 10t motor, 50v 12.3Ah battery, running 30A through 9FET controller. Tops out ~30 mph.

My experience: A = acceleration, V = top speed. In my setup, accel is plenty brisk for general street use, and top speed is more than enough.

 

[dogman dan]

You'll need the bigger battery if you chose the 40 amps controller. The 10 t motor would be enough at 48v. 25 amps of 48v is enough watts to reach 30 mph.

So if you get the smaller battery, get the less amps controller.

 

[Drunkskunk]

Welcome to the forum. The Trek 4300 is a good bike, but the latest model's 8 speed rear will cause troubles. look for something with 7 speeds or less on the rear. I believe older versions used a 7 speed rear.

A 40A controller would be too much for an unmodified MAC, and the 8T while being fast, will overheat faster than a 10T. Your best option is something like what Footloose recomends. 10T, 52v battery, 30 amp controller.

 

[alex220]

If I buy the 7-spd 11 tooth freewheel from cell_man, will if matter which year 4300 I were to get?

Any other good used bike models to keep an eye out for on craigslist? I know a lot of threads cover this but since you know exactly what I want to do, any particular recommendations would be great...

Thanks all

 

[Neiler106]

I would recommend a larger wheeled bike with a mid-drive kit. A 700c rotating at 60rpms will cover more ground in the same amound of time as a 26inch doing 60rpms. The Mid-drive just allows you to take advantage of the gearing. My Electric Giant does 30 on flat land, and its a 48v setup, with a ping battery. It was my first build, and about as plug and play as you can get.

It can be done for about 1000$ plus a bicycle of choice to install it on.

The build was pretty open book as far as the issues I ran into but I can say that once it was built, its worked great.

My Electric Giant Mid-Drive, 1st (and only) buildhttp://endless-sphere.com/forums/viewtopic.php?f=3&t=49594

 

[Drunkskunk]

The problem is the 8 speed would have diffrent shifting distances, so it would never shift right. There is such thing as an 8 speed freewheel, but you would have to stretch the frame to make it fit, and thats not something that always works out well.

The Trek 3500 Disk uses a 7 speed rear, as well as the Trek 820. while the 820 has a lower end componant group and no disk brakes, it is a steel frame.

 

[alex220]

I've got the chance to pick up a trek 820, 2006 it looks like on bikepedia.

7 spd rear

steel frame?

good bike to pick up?

 

[footloose]

Re freewheel / number of gears.
Frankly, I tested to make sure gears actually worked.
Since then, find I leave it in next-to-highest gear all the time.
Will probably be asking ES advice in near future
on converting to a single speed freewheel.

 

[-dg]

I've got the chance to pick up a trek 820, 2006 it looks like on bikepedia.
...
steel frame?

Probably.

Another to look for are the 930/950/970 from the late 80s on. These are steel, sporty, mostly unsuspended but some had suspension forks. They were the more serious mountain bike line, the 800 line was more of a hybrid.

 

[alex220]

Well i just picked up a Trek 820 on craigslist.

Will post some pics for you guys later to see what you think. I have nearly no knowledge of bikes and their parts, thats what I'm trying to learn now, fix up small things, get the maintenance part down before i throw batteries on it.

Rode it around, gears seem to work fine.

Thanks for your help all.

 

[Brentis]

Well i just picked up a Trek 820 on craigslist.

Will post some pics for you guys later to see what you think. I have nearly no knowledge of bikes and their parts, thats what I'm trying to learn now, fix up small things, get the maintenance part down before i throw batteries on it.

Rode it around, gears seem to work fine.

Thanks for your help all.

Post a pic of the dropouts. (I think your good)

Youtube bicycle maintenance vids will save you big dollars if your willing to learn.
Your E choices are sound, keep listening to the pro's advice.
I have purchased from em3ev and cannot recommend high enough.
Welcome aboard. Good luck.

 

[alex220]

okay everyone, I need to search for a new bike. The bike I picked up had too many problems. Technician said the rear wheel was bent, spokes too tight, cables need replaced, derailleur possibly bent, ect. I think he said part of frame may be slightly bent, but could straighten it out possibly.

Should I just use the frame and upgrade to a better rear derailluer, add front disc brake, ect??

Since the mac kit will give me a new rear wheel

 

[alex220]

Also, if i search for a new bike:

1. Must it be steel frame?
2. Do I need disc brakes?
3. Does it need 7 spd rear to work with the MAC motor, even if I buy the 7 speed 11T freewheel from cell_man?

 

[dogman dan]

Ideally a 7 speed rear shifter. But 8 speed can be used with no modifications. 9 speed definitely requires a new chain, new derailur and a new shifter, to convert back to 7 speed.

Alloy is fine, but get a stout frame for the speeds you want to ride. You need a very stiff frame from side to side to pack a load and haul ass. Look for a big triangle space, you are going to need all the space for the battery you can get. Look for lots of strength in the rear dropouts, ideally a larger flat plate that makes bolting on a torque arm easy. Avoid a bike with a rear area that looks like a lace doily.

Disk brakes are good, especially if you are going ahead with an above 30 mph setup. Just disk on the front can be enough. On a high speed panic stop, it's mostly all about the traction of the front wheel.

If your speed will be 30 mph max, v brakes will be fine. When that car right crosses you into the parking lot, you are screwed either way, brakes won't save you. Sliding into a left turn with your brakes on will. Better learn that if you will haul ass on a bike.