Hill Climbing eBike

[E-HP]

My goal was massive weight reduction over a big fat 12mm solid steel axle which would have been stock.

Only time will tell if it can survive the stress I put on it eventually.

The beauty of it is that if something bends or breaks, you can just fix it and reinforce where necessary, instead of overbuilding from the start.

Sooner or later, I'm going to need to invest in a welder. I think over time, the ideal ebike is something you build an image of in your mind, after all the lessons learned, and not something you can just buy and put together.

 

[SafeDiscDancing]

How do you line up the rear wheel to the front wheel or frame to keep everything inline and straight?

That has been a real struggle.

Every time I weld this square tube it always warps slightly.

So this morning I spent trying to get everything straight by heating and shrinking the mild steel. (low quality)

But then when I added these new add ons it put it out of alignment again.

When you use oxygen / acetylene like I do you can heat up a whole area and bend it through shrinkage.

This is one area where higher quality Cromoly steel might be worth the added cost because that stuff is not warping all the time.

Cutting square tubes is easier than round, but the round tubes seem to stay where you put them better.

I'm still pretty confident that I'll end up with a well aligned ending.

One thing also is I think the orginal pivot on the aluminum frame itself is not perfect. When you have a short standard bicycle swingarm of 15" you hardly notice a slight imperfection. But stretch that out to 30" and all the slightest errors magnify. Still hopeful it will work out. You can just keep fiddling until it's where you want it.

 

[SafeDiscDancing]

Sooner or later, I'm going to need to invest in a welder. I think over time, the ideal ebike is something you build an image of in your mind, after all the lessons learned, and not something you can just buy and put together.

Oxygen / Acetylene welding is a very different thing than regular arc welding or TIG or MIG welding.

It's very free form and you either get good at it or you wreck everything you try to weld.

I'm 60 years old and first learned to weld at 16 years old. The good news is you never forget the skill once you know it.

Most people go the electric route with welding and oxygen and acetylene is really expensive these days.

Back when I was 16 you could refill your bottles for $40 but I just paid about $120 for the refill lately. (inflation)

 

[nicobie]

Nothing wrong with gas welding. It's how I started too. Have you tried brazing? It would help with your warping problem. Brass welded thin wall chrome moly makes an excellent frame.

While I've never competed in hill climbs and don't know too much about it, it seems to me that a larger diameter wheel would be a better choice due to the larger tire contact patch. Also the bigger the diameter, the easier it is to get over obstacles.

 

[SafeDiscDancing]

...it seems to me that a larger diameter wheel would be a better choice due to the larger tire contact patch. Also the bigger the diameter, the easier it is to get over obstacles.

True. But the idea is to get more power down at a lower speed... peak power should be about 18 mph.

At 4000 rpm my gear reduction is 10 tooth to 94 tooth using a #219 go kart chain.

Basically the small wheel allows me the potential to "actually" drive it with some honest torque.

A big heavy full sized motocross rear tire would need 20,000 watts to get any drive.

This is also why I'm doing all this "Weight Weenie" stuff to keep this a very light Hill Climbing Ebike.

Total power will be no more than three horsepower... 2,000 watts... one tenth what a big tire might need.

 

[E-HP]

Sooner or later, I'm going to need to invest in a welder. I think over time, the ideal ebike is something you build an image of in your mind, after all the lessons learned, and not something you can just buy and put together.

Oxygen / Acetylene welding is a very different thing than regular arc welding or TIG or MIG welding.

It's very free form and you either get good at it or you wreck everything you try to weld.

I'm 60 years old and first learned to weld at 16 years old. The good news is you never forget the skill once you know it.

Most people go the electric route with welding and oxygen and acetylene is really expensive these days.

Back when I was 16 you could refill your bottles for $40 but I just paid about $120 for the refill lately. (inflation)

It definitely isn't easy to make good welds, but even a novice can spot a bad one. My friend's brother was really good at it high school and ended up going to the welding championships in Florida, around '75 or '76. I think TIG was called Heliarc back then. He took first place in I think 3 categories. I remember his phone was ringing off the hook from companies (and the government) that wanted to hire him when he got home. We thought is was a big deal, since it was his first time on a plane, and it was on the opposite side of the country.

I kind of regret taking woodshop instead of metal shop now. Maybe I could get some tips from him next time I'm in that neck of the woods.

 

[SafeDiscDancing]

I remember his phone was ringing off the hook from companies (and the government) that wanted to hire him when he got home. We thought is was a big deal, since it was his first time on a plane, and it was on the opposite side of the country.

It's good steady employment if you can endure the physical aspects of it over time.

There was a regular at a bar I used to go to who was a welder and he could get work anywhere if he was willing to travel for it.

But getting a regular steady welding job these days is getting harder with all the robots taking over the larger production runs.

Frankly I would not want to do it every day either.

Last week I did work on this for three or four days in a row and took three days off to ride my ebike before starting back at it today.

Also... it's a heck of a lot easier in cool weather than hot. Summer welding is just brutal.

 

[calab]

That rear tire looks like a beast ready to roar :thumb:

 

[SafeDiscDancing]

Just a little heating up and warping the mild steel in the appropriate places and this morning looks to be the "good enough" condition for alignment.

There are still small welds to do adding attachments but I'll be careful about correcting those warps when they happen.

Seems okay.

Today is a good day to build the bike stand.

 

[owhite]

This is meant entirely as a caution -- I'm sure youre building this as a fun welding project and to learn from this -- one concern to watch out for is your long swingarm will impact your riding experience in a lot of ways. The forces that the box construction of a typical swingarm frame are meant to deal with include torsion around this axis:

.

My prediction is that when you turn, especially in a lean, the swingarm will twist and wag in directions that will impact bike performance. I had a similar set of problems described here on my build.

I'm not trying to talk you out of anything -- try it and have fun, that's what this hobby is all about -- just be careful when you first jump on the bike -- especially on downhill turns.

 

[E-HP]

My prediction is that when you turn, especially in a lean, the swingarm will twist and wag in directions that will impact bike performance.

I was under the impression, probably wrong, that the bike was being built for a specific purpose, which doesn't involve much turning, although the twisting could still be an issue.

 

[SafeDiscDancing]

My prediction is that when you turn, especially in a lean, the swingarm will twist and wag in directions that will impact bike performance.

I was under the impression, probably wrong, that the bike was being built for a specific purpose, which doesn't involve much turning, although the twisting could still be an issue.

Guys relax.

This is 1.5" Square Tubing.

It's overkill. Massive rigidity. I know how to build things.

Strength and stiffness is all about angles and braces.

A flat sheet of metal has no angles... so that's why it flexed badly.

Generally you want the biggest tube size matched with the thinnest metal you can get away with.

This square tubing is just 1/16" thick.

Just trying to torque the rear wheel relative to the frame now is impossible because there is no flex.

 

[SafeDiscDancing]

Mostly a lot of sanding to get these parts cleaned up before welding.

Two welds, but this is thick steel (1/8") so right on the upper limit of my usual nozzle.

It's a start. More later.

 

[E-HP]

My prediction is that when you turn, especially in a lean, the swingarm will twist and wag in directions that will impact bike performance.

I was under the impression, probably wrong, that the bike was being built for a specific purpose, which doesn't involve much turning, although the twisting could still be an issue.

Guys relax.

This is 1.5" Square Tubing.

It's overkill. Massive rigidity. I know how to build things.

Strength and stiffness is all about angles and braces.

A flat sheet of metal has no angles... so that's why it flexed badly.

If all goes well, but the impacts seem pretty brutal on the whole bike.
https://www.youtube.com/watch?v=iBjTZIkD6cs

 

[SafeDiscDancing]

If all goes well, but the impacts seem pretty brutal on the whole bike.

This swingarm is strong enough for a small motorcycle... 80cc or so.

I have built bikes before and know what works.

This is massively stronger than needed and in the design process I seriously considered 1.25" square tubing as an alternative.

The funny thing is 1.5" was cheaper. :wink:

But if there is any flex I will sense that in early testing.

Right now I'm very confident it's going to work as planned.

------------------------

Update: I did a calculation on an engineering calculator that does square tubes and it gives a number of 800 lbs before you start to expect failure. Tried to upload an image on this tablet (not my garage tablet) and it won't upload.

Anyway... this Hill Climb Ebike will weigh about 60 lbs and I'm about 200 lbs so overall about one third of the limit.

It could be a problem if I was jumping 35" and landing on it, but this is not intended for that... it's for slow steady hill climbing.

 

[SafeDiscDancing]

More progress on the bike stand.

Enough for one day. (3 hours)

Plenty still to do... another 3-4 hours easily.

 

[SafeDiscDancing]

2 hours.

More to come.

 

[calab]

At least you do something to progress a project in a timely manner.

 

[SafeDiscDancing]

At least you do something to progress a project in a timely manner.

I did some work in the morning then ran a few errands. After that I took the afternoon off.

Henry Ford was a fascist and was all about pushing, pushing, pushing production harder.

Tesla was a thinker.

And Tesla did his own thing... so I'm more Tesla than Ford.

It will get done when it gets done... a hobby is not a job.

 

[calab]

But Ford "invented" the assembly line and employed thousands and spent billions, he even helped out both sides of the world wars.
Meanwhile Tesla was in his lab along with his assistant.
Actually in typical fashion Ford stole the assembly line idea from the meat industry, so Jay Leno says in the Jeff Jefferies podcast.

I did some work in the morning then ran a few errands. After that I took the afternoon off.

Henry Ford was a fascist and was all about pushing, pushing, pushing production harder.

Tesla was a thinker.

And Tesla did his own thing... so I'm more Tesla than Ford.

It will get done when it gets done... a hobby is not a job.

 

[DogDipstick]

Nice to see this coming along.

At least you do something to progress a project in a timely manner.

Henry Ford was a fascist and was all about pushing, pushing, pushing production harder.

Henry Ford calculated how many steps/day a single worker at a single station could make without compromising employee efficiency ( getting the jobs done). He found that if a worker was placed greater than three steps away from the worker next to him, he would waste the time to walk to the next station.

....he found if he placed the workers within two steps of each other, the worker efficiency increased. So he made any two stations less than two steps away from the one next to it. ....

Yes.


For swingarm ( engineering load distribution wthin the beam) inspiration, look at the early CBR 600F swingarm. Not braced, steel, 1" x 2" box section, 90 horsepower. 140mm section rear wheel. This bike was a work of art and won every race for many years. The mooring is very strong with large bearing, and the swinger itself was not very.. strong. High strung, High RPM, tweaky 90hp engine with 43.3lbft @ 8,oooRPM, 12,000RPM red line... and a close ration transmission made for quite the zippyzippy motorcycle..... Some called it " The bike that started it all". 140mph plus top speed,.

Racing Motorcycles then moved, to a very braced, very stiff, large, light, cast aluminum, swingarm, for those power levels, and the F1 Hurricane is now a dinosaur.

Beam load is well enumerated. Steel box section loaded in certain direction is very strong. They did use it in racing motorcycles.

Here you can see how the side load of the spinning wheel destroyed the light swingarm when the motorcycle hit the telephone pole @ 90*. Ridiculously light for the power exhibited. This bike would flex from handling,.. around fast turn. Could still put the power down good, off the corner. Bent like a Banana.

For the most part, it was designed in, the flex. Made to do a job. I think you will be fine.

My prediction is that when you turn, especially in a lean, the swingarm will twist and wag in directions that will impact bike performance.

I was under the impression, probably wrong, that the bike was being built for a specific purpose, which doesn't involve much turning, although the twisting could still be an issue.

Should be OK. Failure there should not cause serious injury, as opposed to front wheel falling off, or steering locking, braking failure, etc.

Guys relax.

This is 1.5" Square Tubing.

It's overkill. Massive rigidity. I know how to build things.

I agree. The rear wheel is very light, you should be fine, with that section, steel box, with a good mooring and good bearing.

My swinger on my hubbie bike is very strong. 18 lb motor, 5 lb tire/rim. High end MTB from 2004. But the bearings in the hub are shot. The whole ass end wiggles back and forth approach 35, 36, 38mph... And stops accelerating there as it wastes its energy wobbling back and forth like a puppy dog / beached fish. Weight wagging back and forth, weaving the bike. Gets such uncontrollable I must slow the bike some times.

It reaches a critical RPM and just shakes like no tomorrow. Shakes so hard, only option would be to decrease speed or the harmonic will resonate at a certain point, and increase the amplitude to the point of zero control.

Lol I gotta fix that.

Lol. Weight.

 

[SafeDiscDancing]

Where I left off yesterday.

This bike stand needs to interface with the swingarm with two cylindrical tubes that will be inserted into two corresponding holes made ready in the swingarm.

Now the trick today is to "create" those tubes (which don't exist in my scrap pile) at a very precise diameter so that they fit snugly enough to not cause unwanted wobble but at the same time not be so tight as to make insertion difficult. This means taking a bigger tube and cutting it and welding it then grinding it. Plus I want smooth domes on top of the tubes so that's another bit of finesse I need to do.

The other big problem is the holes in the swingarm will be at an angle to the floor so I'm going to have to guess a bit on exactly how much tilt I insert.

The goal is to have a bike stand to test the motor but it also needs to be sturdy and stable enough for someone to sit on the bike while on the stand.

Because if you don't design to support a human eventually a stupid human will use it anyway and wreck your stand.

And hopefully I'm never "that" stupid human.

All the metal I'm using on the bike stand is my "B" grade scrap that often has weird bends in it. It also tends to be heavy but it will be very strong.

I like bike stands more than kickstands. This adds no weight to the bike and the only time I really need a bike stand is when I'm done riding and the bike is in the garage.

 

[DogDipstick]

The other big problem is the holes in the swingarm will be at an angle to the floor so I'm going to have to guess a bit on exactly how much tilt I insert.

The goal is to have a

I like that frame configuration because of the high pivot point of the swinger in relation to the bottom bracket and corresponding chain force that will extend the swing arm upon application of power. One of the reasons I have thought about this very GT frame many times in the past.

The triangle created through the loaded path of articulation, vs the chain normalizing force, is good for a hill climb bike, given the front sprocket not be to large.

I would set it up so that you have ample travel at loaded sag.

 

[SafeDiscDancing]

I like that frame configuration because of the high pivot point of the swinger in relation to the bottom bracket and corresponding chain force that will extend the swing arm upon application of power.

That's another key point.

The motor will be mounted on the swingarm itself near the rear wheel. (under three pounds)

So I'm not dealing with a long chain on the motor drive.

The pedal chain will be long however, but we will see if pedal power induces any flex.

Just by feel I can sense this swingarm is rigid.

I have gone through the slow and tedious process of heating up the swingarm and bending it into alignment so I have literally tried to torque on it and it's stiff.

The online engineering calculator estimates 800 lbs is the yield strength for 30" of 1.5" square tubing... it feels like that.

 

[SafeDiscDancing]

Hopefully this view gives a better sense of the sheer bulk of this swingarm.

Compare these 1.5" square tubes to the skinny forks... they are about 1".

I think this view should calm the "nervous nellies" about it being strong enough.

---------------------------

Just had a thought.

I probably should build the shock mount first and finish up on the rear wheel.

Then get a rough sense of where the shock will likely be set to.

Until I get vague sense of where the shock will go I cannot know the angle of the swingarm and without knowing that I can't set the bike stand properly.

So I need to change the build sequence.