First E-recumbent and custom bike build.

[sloaaron12]

Hi guys.

So I just recently got into E-bikes after a friend of mine built his and stumbled onto this forum. I've been reading up the past week and finally feel knowledgeable enough on the subject to start my own build. I'd just like some opinions on my proposed design to see if anyone can point out significant flaws and give some constructive criticism. I'm building this bike as a my main way to get to and from work.

I'm building the bike so that it will be able to cruise at 30 mph (with pedaling), have a top speed of 40mph (also with pedaling), and have a range of 40 miles at cruising speed. For this to be possible I'm considering a rear Cromotor, a 48V 40ah battery (overkill?), and dual suspension. Controller, BMS, and cycle analyst are still up in the air. I'm still finalizing the design and my main concern right now is the integrity of my frame. My proposed design is attached. If its made of steel, will it be able to hold up to the stresses I'm proposing? I'm also concerned about the angle of the front fork. How difficult will that make turning? I'll be riding on two-lane streets so sharp turns won't be too big an issue; I should have plenty of room to turn and doubt U-turns will be necessary.

Any thoughts or suggestions would be appreciated.

Edit: In the sketch, red signifies shock support and yellow is a hinge.

 

[migueralliart]

I'm gonna quote someone else on this one

Please go to the User Control Panel, select Profile, and then enter your city, state/province, and country into the Location field (country minimum) and save it. This will help people help you. Example: Wylie, TX, USA. Without knowing what country you are in it's hard to make any recommendations. Thank you.

Now onto your drawing .

NO ONE in the world will be able to tell you if that frame is going to hold up to the stresses you are gonna experience based only in your sketch.

Besides that why are you building such a complex frame. With all that money can't you just buy a recumbent already made?

Cro motor will handle that speed but that voltage doesn't seem right. Others will chime in regarding this.

 

[sloaaron12]

Ok I changed my settings, thanks for the help getting started here.

I know that no one can tell me "Oh that looks perfect." but I figured, based on geometry, that someone could give me a "yeah looks about right" or a "no add some support here". Like I said, I'm still in the design phase and I have no experience building bike frames so I'm just shopping for opinions I guess.

As for frame complexity, I prefer to err on the side of caution. But I can always build simpler and add support if need be. I ask this because I haven't yet seen a recumbent/chopper design like I'm proposing so I have nothing to base it off of.

Edit: which part do you think is overkill? The double front supports?

 

[agniusm]

I'd say forget it. Dont waist your time. Your drawing says nothing. Start building simple frame, it will be coplex enough for you. Get in to scrap yard, get some frames and start chopping. When you have no idea what you doing trial error way is good start. Things look simple until you start making. Start with rigid frame.

 

[Thud]

Study materials for you:
http://www.rqriley.com/xr2.htm
http://www.atomiczombie.com/DIY%20Plans.aspx

Building a frame from the ground up is no small undertaking.
I wont say a word to discourage you.

A couple questions.
Any experiance with recumbents currently? I would find a shop or club that will let you test ride something before comitting a pile of cash & time into it.
Do you have a few friends with the fab skills to tackle the project? Or are you going to use it as a learning experiance.
Any way, i love a good build project, good luck & have fun with it.

 

[sloaaron12]

Study materials for you:
http://www.rqriley.com/xr2.htm
http://www.atomiczombie.com/DIY%20Plans.aspx

Building a frame from the ground up is no small undertaking.
I wont say a word to discourage you.

A couple questions.
Any experiance with recumbents currently? I would find a shop or club that will let you test ride something before comitting a pile of cash & time into it.
Do you have a few friends with the fab skills to tackle the project? Or are you going to use it as a learning experiance.
Any way, i love a good build project, good luck & have fun with it.

Thanks for the references, I can't wait to look through them when I get home.

I have moderate fab skills (some welding in high school and more in college) and my uncle has built many cages for various vehicle so I think I'm set there. It will definitely be a learning experience as I've never committed to a project of this size, but I don't think it's impossible. I still have a few months before I start classes again (and get access to my school machine labs), so i have a while to get all the specifics down before I start on the build.

I know that this project will be no small endeavor but I'm excited at the prospect of riding a bike that was built from the ground up for me, hence why I wont go and get a premade bike. Plus I don't like the aesthetics of normal recumbents.

I'd say forget it. Dont waist your time. Your drawing says nothing. Start building simple frame, it will be coplex enough for you. Get in to scrap yard, get some frames and start chopping. When you have no idea what you doing trial error way is good start. Things look simple until you start making. Start with rigid frame.

That's a great idea, I'll start looking around some junkyards for frames that will be of no real loss if I screw them up.

As complex as it is though, what do you guys think of the frame design? Specifically the suspension that I'm proposing for the rear end. I really wish I had access to autoCAD on my computer so I could give you a better idea of what my plans are...

 

[Drunkskunk]

The sketch looks good, maybe. I see some issues you may want to consider.

With the rear suspension pivot so high, your suspension will "jack" under power, and collapse under braking. The pivot point needs to be inline with the direction of thrust. With all your weight in the rear, you're going to want more travel that that desiggn appears to have.

You have a chopper bike angle on that front fork. And you're on a recumbent. Both factors make low speed handling a real b1tch. that Steep steering angle will also make the front wheel want to skid in corners and will make most forms of front suspension ineffective. a tube type fork won't compress when going over a bump when laid back that far.

Consider that the speed you want to cruse at is going to use 4 times the power most bicycles parts were designed for. In fact, your performance goals are beyond what mopeds were designed for. If you want to use this as a commuter, you should consider mixing moped/light motorcycle parts, at least as far as wheels, tires, and brakes.

And finally, forget about pedaling being anything that contributes to your speed at 40mph. A normal Ebike takes around 3000 watts to go 40. The 150 watts you can contribute will do nothing meaningful.

 

[sloaaron12]

The sketch looks good, maybe. I see some issues you may want to consider.

With the rear suspension pivot so high, your suspension will "jack" under power, and collapse under braking. The pivot point needs to be inline with the direction of thrust. With all your weight in the rear, you're going to want more travel that that desiggn appears to have.

You have a chopper bike angle on that front fork. And you're on a recumbent. Both factors make low speed handling a real b1tch. that Steep steering angle will also make the front wheel want to skid in corners and will make most forms of front suspension ineffective. a tube type fork won't compress when going over a bump when laid back that far.

Consider that the speed you want to cruse at is going to use 4 times the power most bicycles parts were designed for. In fact, your performance goals are beyond what mopeds were designed for. If you want to use this as a commuter, you should consider mixing moped/light motorcycle parts, at least as far as wheels, tires, and brakes.

And finally, forget about pedaling being anything that contributes to your speed at 40mph. A normal Ebike takes around 3000 watts to go 40. The 150 watts you can contribute will do nothing meaningful.

Yeah that's what I was concerned about, with the angle its at I'm assuming it will "edge in" and slip very easily. I know that the issue would be solved by increasing the slope.... but then it wouldn't look as cool Will fatter tires help (motorcycle thickness) help at all or do you think any good effects will be negligible? And wouldn't it be possible to pedal at higher speeds if I increased the size of the gear?

I knew this design might cause some complications but I as hoping it would still be ridable... Thanks for responding and voicing your opinions on the matter.

 

[agniusm]

U csn use a U joint for your steering while keeping propper steerer tube angle:

 

[bowlofsalad]

The strength of something is relative. But you'd probably do well do base your work around of 14ga square steel tubing. Assuming you have some cash to spend, it's a no brainer to go with a123 cells with a BMS (see em3ev). With a tube notcher and some skill, you can use round tubing for your build, but that is up to you. Designing the frame isn't super easy. I'd just shoot for over kill though, meaning using thick material and perhaps adding extra bracing around critical joints that might take a lot of abuse. This might end up being a heavier bike (Not the end of the world with an ebike), but you won't end up stranded, on the side of the road, late, or injured because something broke. I am actually planning on working towards making an extremely similar (if not identical) concept for a bike frame myself. The concept is often called a lowracer. A lot of people will probably argue that being very low is dangerous, it may be, just be sure to do things that will enhance your ability to draw attention. It's interesting that others are working on doing the same thing.

MIG is a great form of welding. I am assuming you aren't the most experienced fabricator, as your experience is limited to school it sounds like. That is what I would stick with. For some reason a lot of people are into TIG welding, unless I was doing titanium or chromoly, I wouldn't consider it, it's not worth it unless you are already extremely good at it and so on.

Some people are think aluminum is stronger than steel on a weight to strength ratio, it is not, they are about the same. There is a lot of debate on which could be stronger, but that is irrelevant. The critical idea here is, steel has a fatigue limit, aluminum does not. Steel will bend where aluminum will crack. Think of steel like cardboard and aluminum like glass.

If you don't have access to all the tools you'll need, getting setup is rather expensive. The beauty of making things yourself is, tools don't (typically) break after one use, many tools will last a very long time, and if something goes wrong or breaks you will be absolutely prepared for fixing it. The biggest gain for making things yourself is gaining the skills to do so for future tasks or projects. Do be detoured by anyone on this, it's absolutely worth it. Go for it.

Where are you going to mount the batteries? In my mind, there are a couple of logical options. One is straight behind the rear wheel, not above it, and the other is in front of you, perhaps a slightly longer wheel base or something. I don't know how much thought you've put into all this. But, this detail doesn't seem apparent (sometimes I over look things).

 

[Lebowski]

have you thought about just bolting the thing together, not using a welder ?

http://www.n55.dk/MANUALS/SPACEFRAMEVEHICLES/spaceframevehicles.html

 

[bowlofsalad]

have you thought about just bolting the thing together, not using a welder ?

http://www.n55.dk/MANUALS/SPACEFRAMEVEHICLES/spaceframevehicles.html

I have, I wouldn't be surprised if this thought crosses the mind of most people who are considering making something out of metal. There are pros and cons to all things. For a while, I was considering making bike frames out of wood and drilling screws to keep it together, it still, at times, sounds like an appealing thought.

Although, most of the times I've cast off these two kinds of ideas relates to lack of engineering knowledge (Can I make it strong enough with certainty?), or fear (how reliable can I make this?). I only recently learned about nord lock washers, and hilariously, that video on the holding power of nord lock washers really educated me on more than just the nord lock washers.

I think what it'll boil down to for most people who make a frame is asthetics if its an option. I might be wrong, but I think plenty of people would much rather own a bicycle with round tubing with a sexy sleek look to it. It's really sad in a lot of ways how vanity is such a critical element for so many ideas.

 

[torker]

+1 on checking out Atomic Zombie website. Also checkout http://www.bentrideronline.com/messageboard/index.php Lots of good info. I have built 2 recumbents. A toureasy clone is my favorite. No suspension but really nice with big tires. The main thing to consider for low speed handling on a bent ( recumbent) is rake and trail. It is the relationship between angle of the headstock/forks/size of tire and this can be adjusted with tire size and the bend in the forks. I would build one and make it ridable before ever adding electric. Good luck and welcome to ES

Here is the TourEasy clone

 

[sloaaron12]

U csn use a U joint for your steering while keeping propper steerer tube angle:

Wow. That is dead sexy. That's the exact aesthetic I'm trying to go for: long, slim, and streamlined. I'll definitely look into U-joints. It's good to see that my design is possible!

I just drew up a scale design of what I'm going for, after taking your guy's suggestions into consideration of course. I raised the slope of the front fork to increase handling and shock absorption.

The strength of something is relative. But you'd probably do well do base your work around of 14ga square steel tubing. Assuming you have some cash to spend, it's a no brainer to go with a123 cells with a BMS (see em3ev). With a tube notcher and some skill, you can use round tubing for your build, but that is up to you. Designing the frame isn't super easy. I'd just shoot for over kill though, meaning using thick material and perhaps adding extra bracing around critical joints that might take a lot of abuse. This might end up being a heavier bike (Not the end of the world with an ebike), but you won't end up stranded, on the side of the road, late, or injured because something broke. I am actually planning on working towards making an extremely similar (if not identical) concept for a bike frame myself. The concept is often called a lowracer. A lot of people will probably argue that being very low is dangerous, it may be, just be sure to do things that will enhance your ability to draw attention. It's interesting that others are working on doing the same thing.

MIG is a great form of welding. I am assuming you aren't the most experienced fabricator, as your experience is limited to school it sounds like. That is what I would stick with. For some reason a lot of people are into TIG welding, unless I was doing titanium or chromoly, I wouldn't consider it, it's not worth it unless you are already extremely good at it and so on.

Some people are think aluminum is stronger than steel on a weight to strength ratio, it is not, they are about the same. There is a lot of debate on which could be stronger, but that is irrelevant. The critical idea here is, steel has a fatigue limit, aluminum does not. Steel will bend where aluminum will crack. Think of steel like cardboard and aluminum like glass.

If you don't have access to all the tools you'll need, getting setup is rather expensive. The beauty of making things yourself is, tools don't (typically) break after one use, many tools will last a very long time, and if something goes wrong or breaks you will be absolutely prepared for fixing it. The biggest gain for making things yourself is gaining the skills to do so for future tasks or projects. Do be detoured by anyone on this, it's absolutely worth it. Go for it.

Where are you going to mount the batteries? In my mind, there are a couple of logical options. One is straight behind the rear wheel, not above it, and the other is in front of you, perhaps a slightly longer wheel base or something. I don't know how much thought you've put into all this. But, this detail doesn't seem apparent (sometimes I over look things).

I'm looking into a free AutoCAD solution so I can really get into this frame design. How aesthetically pleasing the actual frame is isn't as important to me since it'll be covered with a fiberglass body. I'm probably going to go with square steel for the frame. I figure that will be the easiest to work with.

And yes the battery will be going in front of me between the two bars that support the fork... I probably need to make that space larger though. I've been thinking about this bike all day for the past week :lol: I've put a lot of thought into it so far but a lot of my ideas still remain in my head. Do you mind sharing with me what your building? I'm very curious.