Considerations for building mid-drive e bike from scratch/frame up?

[neptronix]

14" seems a little small unless we're talking about a woman's frame ( these are measured differently due to their much lower seat post )

If you can tolerate a regular mountain bike then that would be best for frame strength ( becomes important when going fast speeds )

Mounting a battery and other things in the center of the frame is best for weight distribution. Put a battery on the rear, and the rear will wag. Put it on the front, and the front will wag. All due to the battery's weight.
But in the middle of the frame, you won't notice the weight at all.

Ideally on a women's bike, you use the top tube to mount a battery because this is as close as we can get to neutral weight.



For other cargo, rear is ideal because if the wind blows sideways on a front loaded cargo, it will turn the handlebars with the wind. I find it's less dangerous to have the air hit the rear ( way less counter-correcting for wind is needed ).

Once bikes start going fast ( BBSHD is a pretty fast drive, capable up to 34mph on stock-ish power ), they start becoming less forgiving, handling wise. Suddenly you want a longer wheelbase, better front suspension, good weight balancing, stronger brakes, etc with this ~2x speed increase vs pedal bike speed

 

[Tortoined Grower]

14" seems a little small unless we're talking about a woman's frame ( these are measured differently due to their much lower seat post )

If you can tolerate a regular mountain bike then that would be best for frame strength ( becomes important when going fast speeds )

Mounting a battery and other things in the center of the frame is best for weight distribution. Put a battery on the rear, and the rear will wag. Put it on the front, and the front will wag. All due to the battery's weight.
But in the middle of the frame, you won't notice the weight at all.

Ideally on a women's bike, you use the top tube to mount a battery because this is as close as we can get to neutral weight.

View attachment 367395

For other cargo, rear is ideal because if the wind blows sideways on a front loaded cargo, it will turn the handlebars with the wind. I find it's less dangerous to have the air hit the rear ( way less counter-correcting for wind is needed ).

Once bikes start going fast ( BBSHD is a pretty fast drive, capable up to 34mph on stock-ish power ), they start becoming less forgiving, handling wise. Suddenly you want a longer wheelbase, better front suspension, good weight balancing, stronger brakes, etc with this ~2x speed increase vs pedal bike speed

Damn, that's some good info to consider. Seems like I just keep losing the battle for the perfect frame everytime though lol.

 

[neptronix]

Just buy something completely boring but strong, ie a front suspension mountain bike or ladybike equivalent of

ps bikeisland sells returned bikes from bikesdirect if you are looking for really cheap:

BikeIsland.com - Bicycle Parts, Accessories and Clothing at Affordable Prices with Free Shipping

 

[amberwolf]

Damn, that's some good info to consider. Seems like I just keep losing the battle for the perfect frame everytime though lol.

That's why I started building my own....

Even if it's just modifying an existing frame (or whatever) to fit my needs better, instead of something completley custom built like the SB Cruiser. (for instance, the original CrazyBike2 was built from some small Magna frame that looks a lot like the blue bike Neptronix posted above, for the front frame, and then an old Schwinn ten speed for the back with teh seat tube cut way down and the stays and top tube bent down to line up with the new top a few inches above the BB).

Building or modifying your own frames is not an option for most people, but wherever it is, it certainly makes things easier!

 

[amberwolf]

For other cargo, rear is ideal because if the wind blows sideways on a front loaded cargo, it will turn the handlebars with the wind. I find it's less dangerous to have the air hit the rear ( way less counter-correcting for wind is needed ).

One way to minimize this is to extend the top tube forward over the wheel (several non-welding ways to do this) and mount your rack to that instead of the fork or bars. It will still be pushing hte front of the bike but not actually turning the bars and it's much easier to correct--pretty much the same as on the rear.

 

[Tortoined Grower]

I think I have been fixating too much on the rear bag as an absolutely necessary installation. Compromising with paneer bags would allow me to mount the bike traditionally and I honestly don't know how I haven't thought about this until now.

Just buy something completely boring but strong, ie a front suspension mountain bike or ladybike equivalent of

ps bikeisland sells returned bikes from bikesdirect if you are looking for really cheap:

BikeIsland.com - Bicycle Parts, Accessories and Clothing at Affordable Prices with Free Shipping

No shipping to Canada : (

 

[Tortoined Grower]

I think I have been fixating too much on the rear bag as an absolutely necessary installation. Compromising with paneer bags would allow me to mount the bike traditionally and I honestly don't know how I haven't thought about this until now.

No shipping to Canada : (

I wrote a new message over an old draft, hence the non sequitur beginning of this reply lol.

 

[E-HP]

Thanks again for some information I wouldn't have considered, I'm 5'9 and my leg inseam is around 30" or so. I also have a suspension seat post I forgot to mention that adds 4 inches to the bike seat height.

You just need to find the right frame.
I'm the same height and inseam as you, use a Thudbuster LT seatpost, and was 170lb before Thanksgiving. I'm have a medium size (17'-18") hardtail mountain bike frame with rear rack and 160mm front suspension fork. My toptube angles down a fair amount, but the triangle can still hold a 28Ah battery pack. I found going from 26" to 24" wheels made a big difference in comfort, handling, and for panic stops (I'm too old to get behind the seat, so I get in front of the seat and low if I'm really on the brakes). I cut down the elastomers a little on the Thudbuster to give it more sag. I'm barely on the balls of my feet at an intersection, or I can comfortably put one foot down and the other on the pedal.

 

[Tortoined Grower]

You just need to find the right frame.
I'm the same height and inseam as you, use a Thudbuster LT seatpost, and was 170lb before Thanksgiving. I'm have a medium size (17'-18") hardtail mountain bike frame with rear rack and 160mm front suspension fork. My toptube angles down a fair amount, but the triangle can still hold a 28Ah battery pack. I found going from 26" to 24" wheels made a big difference in comfort, handling, and for panic stops (I'm too old to get behind the seat, so I get in front of the seat and low if I'm really on the brakes). I cut down the elastomers a little on the Thudbuster to give it more sag. I'm barely on the balls of my feet at an intersection, or I can comfortably put one foot down and the other on the pedal.

I really did feel the difference when trying out different frame sizes today, most were 27.5" tires with different frame sizes. I like to have my feet firmly on the ground when I'm at a stoplight, I find that a 17-18 inch frame is way too much with the added height of my sr suntour and cloud 9 seat. Also, did you mean you prefer the 26 inch wheels over 24, or vice versa?

 

[Tortoined Grower]

Oh boy, I may have been a little too far with the cloud 9 and suntour. When bottomed out this setup is 8.5" tall from the top of the seat tube to the top of the saddle. I may be boned with anything other than a 14 inch ladies frame, assuming the tires are still 27.5".

 

[neptronix]

I have the legs of a 6'2 person and i can ride a 21 inch frame with just that setup. But it's tippy toes at a stop.. which is why i run a smaller rear wheel.

A thudbuster LT and a much thinner seat like this would be less tall and more comfortable than what ya got currently:
Selle Royal Freeway Gel Bike Saddle/Bicycle Seat Nice | eBay

Having your feet fully hit the ground would require running a 26" on the back of a 29er, and that would look goofy.

You might want to look for a crank forward bike bike like such:
Flat Foot Technology

Extreme end of that:
Bicycle | Comfortable riding | flat footed stance | Light weight | Pedal Forward | Neck issues | Wrist falling asleep.

 

[gromike]

Yeah, a seat with springs on top of a suspension seat post is redundant. I'd skip the springs in the seat and use your SunTour suspension seat post. I know they work 'cause I got one.

 

[E-HP]

Oh boy, I may have been a little too far with the cloud 9 and suntour. When bottomed out this setup is 8.5" tall from the top of the seat tube to the top of the saddle. I may be boned with anything other than a 14 inch ladies frame, assuming the tires are still 27.5".

I’m using the Cloud 9 with elastomer springs. I think it’s shorter, but the Thudbuster is taller than the Suntour.

 

[glennb]

This disvussion has me confused. Sounds like the objective is to be able to ground feet while perched on the saddle.

If so, you'd need a very slack seat tube angle, likely at least 60 degrees. It's not normal. Normal is sliding forward off the sadfle and putting a foot down, leaving one on the pedal.

 

[Tony01]

No, you’re not building something from scratch until you need to solve a specific problem… but you can select a suitable MTB with good shocks and components, hydraulic disc brakes, chromoly steel frame, and put a mid or hub ebike kit on it and it will be faster and better the more you put into it in diy components

 

[bananu7]

This disvussion has me confused. Sounds like the objective is to be able to ground feet while perched on the saddle.

If so, you'd need a very slack seat tube angle, likely at least 60 degrees. It's not normal. Normal is sliding forward off the sadfle and putting a foot down, leaving one on the pedal.

Yeah, re-reading through this thread has got me similarly confused. What would help would be some shorter cranks, as then you can lower the BB, but you always need some clearance that will put the seat higher than fully extended legs from the ground.

I'd ditch the whole springly saddle/seatpost and look for something like this:

source: Carry — Colin Reay
P.S. I've only now noticed that this frame doesn't even have pedals at all. Probably for the better.