Electric Vehicle Part II: Frame Built

So the frame of the vehicle when last discussed was a highly non-structural frame with a seat some wheels and a motor. This is it now:

A much more structural thingy with a base board and supports and hot damn it even has a chain to transfer power. This thing is almost usable. All of the making the fork and headset and such happened of the course of a few months of off and on work. The making it structural bit happened in about two weeks of more dedicated work. This thing has existed too long in a semi constructed shape, hopefully it will be done soon; or at least rideable its hard to say when a project is done because then the mods and shiny bits start getting added.

 How ever on that note time to talk about structure a lot of the 80/20 carts made at MITERS have been planar creations supported by the sheer shear strength of the aluminum beams they sat on.  Since this bike/EV/thing is like 1.5m long and made out of 20mm 80/20 bars that wasn't going to fly. What the vehicle really needed was a larger moment of inertia to prevent flexing in the middle. This was achieved through the angular braces that form a bridge like structure under the seat. The ends of this bridge structure sit on horizontal bars that are fixed in between 1/4" plates this provides a solid base near the ends of the scooter. Unfortunately this meant the 80/20 had to connect at strange angles, this required bent brackets to accommodate the angles needed by the supports.

Rear brackets

Here is a picture of a bent and yet to be bent pair ofrear brackets. The aluminum is 1/8" thick and for size reference the holes are 20mm apart and fit M5 screws. That also gives a reference for the wrench in the next picture as a poor-man's brake. It is fucking huge. It is around 2' long and provides an excellent lever arm.

Each bracket was bent in small increments deforming one section at a time along the bend line. Despite the inaccurate method the brackets fit in place pretty well. Some brackets which needed larger angles were heated with a torch before bending this made it significantly easier to bend some of the brackets without ruining the intergrity of the metal(...well maybe its temper was ruined but w/e).

Whats was actually more obnoxious than the bending was cutting some of the 80/20 sections. Distinctly the braces on the rear of the vehicle. In order to provide natural support for the braces (both in the front and in the back) they were cut with a niche in the bottom so they could rest on top of the the brackets and supports on the frame base. Due to the odd 3-D angles getting the interface was a pain without using a mill but since I wanted to get this done quickly and precision was not a requirement the joints were band sawed then filed a bit.

Etched cut to make

Left: Cut Just made by bandsaw, chunk barely held in Right: mirror support without chunk of aluminum in place.

Yes that cut looks weird but that is actually how its supposed to be. When viewed from the proper angle it is just a 90 degree cut out like this:

Support bar from a less confusing angle

The angle in the end of each support fits over the edge bar or bracket it connects to, this way when some one is sitting on the scooter and these bars are loaded in compression and they transfer the forces more directly to the structural objects they sit on rather than the brackets that keep them in place. It also means I don't have to worry about them becoming displaced as easily   Either way not very exciting yadd yadda, after attaching the additional supports and what not the electric vehicle was quite solid. After the supports a large sheet of 1/2" plastic(it might be HDPE) that I found was fixed to the base. These steps are kind of boring and I'll skip posting more about the structure of this thing. It's a frame in the shape of a bike/scooter. The next discussion will be about the drive train/energy storage of the scooter.

Also holy crap I'm tired of referring the 'the electric vehicle' as a scooter , EV, minibike. From now on it shall be known as busscooter because it is long like bus and according to some people will have the turning radius of a bus....which is not entirely inaccurate given its length.

Electric Vehicle coming along Part I

So in the mean time of not posting I've been making an electric vehicle for small motor.

It kind of like a minibike..ish. Its been called a skate board crossed with a scooter among various other things, but nothing seems to describe it right. Either way its coming along and its about time for the post of the project. To start off here's the (partially incomplete because I'm lazy) cad model of the project:

Despite being incomplete the vehicle is pretty much the same shape as the cad model. However there were several changes to the structure of the vehicle that were just done on the fly. Namely all the additional supports besides the vertical posts holding the seat up. But I'll get to that in the next post.

The bike was meant to be ridden in the 'superman' position. This vehicle really borrows a lot from other vehicles that have been produced by other people at miters, hence the 80-20 frame. However unlike most of the other 80/20 vehicles that seem to get made the mini bike will be non planar. Partially because the 80-20 extrusions are too thin with out more support (20mm metric is being used rather than 1").
In retrospect it was a bad decision to use 20mm framing for this, not because it is skinny but because the 20mm 80/20 on mcmaster carr uses M5 nuts/screws and its difficult to find M5 tabbed weld nuts of the proper dimensions (at least in quantities less than several thousand) which forces you to buy the expensive proprietary ones actually meant for the framing. If it had been made with 25 or 30 mm extrusion the frame would have been quite heavier not to mention more expensive but the price difference might have been compensated for if I was to using generic nuts.

Time to go over the construction of the vehicle:

One of the first things to do for the vehicle was to figure out the steering for the project. The wheels picked out were unfortunately too wide for a standard bike fork. So a fork was made out of a bike The tubes were roughly cut then milled to the proper angle and size. Then roughly fit together and welded

Partially machined tubes

Machined tubes fit being fit together and the welded fork.

 After welding the main portion of the fork together some steel plugs were turned and cut to fit into the ends of the fork. These were welded into the fork and will hold the shaft/wheel assembly.

Steel plugs inserted into fork

The plugs were then welded in place then flats were milled onto the sides and a 1/2" bit was drilled through for the shaft which is also 1/2". 

Fork awkwardly clamped down ready to get its flats

Note: the welds were ground down because they looked ugly. The welds seem solid though, after attempting to break them several times unsuccessfully, they're expected to be strong enough to hold a mildly obese person.

plugs with holes going though fork

A chunk of steel was turned down to act as the fork crown and support the bottom bearing of the headset and the bearings were press fit into the head tube.

Ghetto step welded on now the Y of the fork is a complete mass of ground down  weldedness

Next step was to make a method of attaching the head tube to the rest of the frame. 

I kinda winged it and welded  some 1/8" steel U-channel to make an attachmenty thingma dig, it takes x2 M8 bolts in the bottom to hold it on the front brace of the rest of the frame. Here is the head set/fork mounted on the frame base:

It was a giant floppy mass at this point but I get into the rest of the structural details later.

Those little orange wheels were obtained from harbor freight for a disturbingly cheap price of like $8.50 a piece. They came with a matching pair of disturbingly crappy bearings; after watching someone else using the same wheel destroy their bearings, I decided it would be best to preemptively swap them out for a better set.

 The old bearings were removed and a spacer was placed in the center of the wheel that would hold a bearing on either side. The new bearings were then press fit in up to their retaining rings, but the spacer was over sized slightly to make sure that it would contact both inner bearing races.

Turning down one of the spacers.

Spacer next to bearing

Bearing on spacer

Spacer and bearing in hub of wheel

The in-hub spacers remove axial loading on the inner bearing races.This allows the wheels to be tightened in place without stressing the bearings in a bad way (these were normal roller bearings not meant for high axial loading) as well as transfer axial forces to both bearings at the same time. Here is a ghetto mspaint illustration of the hub/bearing assembly:

The hub spacer forms a bridge between the two hub bearings effectively making a solid column, making sure that both of the inner bearing races are supported at the same time.

The next step was to actually get handles bars on the bike by making the bike stem. In the course of this the main thing learned was that the bike stem was not called the 'handle bar holder'.

Started with a large chunk of aluminum

Drilled some holes for a flexture clamp to hold the handle bars and reamed a larger hole to take the top of the bike fork

Repeated process on the other side of the block but drilled holes for  the clamp of the fork and drilled a larger hole to hold the handle bars. Then the front was rounded while being held very awkwardly (read: improperly) in an indexing head note: I would highly recommend against doing this for various reasons. The stem was sanded a bit afterward so it didn't look like it'd been chewed on by an angry aluminum hungry dog.

The rounding was kind of a pain in the ass so on the other side the corners were milled off at 45 degree angles .
Also note the larger holes were slit on one side using a band saw, the slits are roughly 1mm wide but it seems to be plenty of room to get effective clamping force.

The complete stem installed, a homemade cap was installed to connect to the star nut in the top of the fork

Bike with temporary handle bars installed... it also grew a seat and a motor in this picture but we can talk about that later.

Yay it's finally a rolling frame. But it has no support structure and I would not bet it on holding any one with that skinny 20mm 80/20 frame. This part actually posed some annoying requirements since 80/20 framing really doesn't do angles well unless you make your own brackets for it. It probably would have taken less time to learn to weld aluminum and put the frame together at this point each joint has too many nuts and screws it both seems annoying inelegant and pain in the ass to make. That being said this post

 feels really long so talking about how this flat floppy frame was made structural will be talked about in part II  of this post.