The ebike parts designing thread with CAD/CAM

[spinningmagnets]

Have you ever had an idea for a custom part that would help you with a custom ebike system design?

I think the best example of this is the Big Blue Saw / BBS thread.
https://endless-sphere.com/forums/viewtopic.php?f=31&t=48811

I have used them and I was happy with the result. They have a proprietary CAD (computer aided design) program that is very easy to use. It has a grid using 1/16th of an inch for the squares. I wish they had a 1mm grid option (one mm is 0.039 inches, 1/16th is 0.062 inch). Its not that a finer resolution is better (although that is good), I just like having metric as an option...

Of course, the problem is that...if you draw something in the 2D BBS program, you can only have BBS make it for you, and also...they don't do 3D-printing.

Water-jetting and laser-cutting can make a complex 2D metal part very easily. Like torque-arms, or mid drive motor mounting brackets. Some of the cost of the parts is the time for set-up, so...if you only need one part, it will be pricey. If you order five of the same, there is a break in the price for each piece, and 10 or 20 is even better. If you have a clever design, it might be easy to sell the other sets, so you end up with one set a better price.

I also want to kick off this thread with an open-source 3D-print in plastic, of my design. There are services that will print-out your 3D part in plastic and ship it to your home. But...someone has to draw it. Eventually I want to learn how to draw parts so I can 3D print them. I have heard good things about Rhino and Googles Sketchup, and recently I have had Fusion-360 and FreeCAD recommended for my project.

As this thread evolves, I will list 2D/3D drawing programs that are recommended, and also services that will print your 3D design and ship it to you. I would also like to list ES members who have a 3D printer, and those list members who have 3D drawing skills that they are willing to perform for a fee.

Here is aluminum plates cut to have interlocking fingers at the edge, which will be welded. I have also seen this method used for laser-cutting wood for similar parts.

https://endless-sphere.com/forums/viewtopic.php?f=3&t=12847&start=500#p1278057

And here is another example...

 

[spinningmagnets]

Recommended CAD programs
("Computer Aided Design" for drawing a 2D / 3D part)

FreeCAD
OpenScad (https://endless-sphere.com/forums/viewtopic.php?f=3&t=90058&start=25#p1313481)
Sketchup
Fusion-360 [student license]. Based on the much more complex professional-AutoCAD
Big Blue Saw (only 2D, and also proprietary)

Can you already draw in CAD? and convert it to a CAM file?

Please post below or PM me, you can make money in your spare time drawing parts.
If I list your user-name here, and then you change your mind later...I can remove your name at any time.

 

[spinningmagnets]

If you have a CAM file (a drawing of a part), who will make it?

This section will be a list of services that will take a CAM file and convert it to a physical part. CNC, 3D-print, laser-cut or water-jet

CNC:

xxxxxxxxxxxxxxxxxxxxxxxxxxxxx

Water Jet (2D aluminum and stainless steel):

Big Blue Saw
http://www.bigbluesaw.com/
https://endless-sphere.com/forums/viewtopic.php?f=31&t=48811

xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx

Laser-Cut (2D steel, plastic, wood):

Precision Wire EDM Service (Michigan), 616-453-4360, kimr@pwedm.com, http://pwedm.com/

xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx

3D printing:

 

[spinningmagnets]

reserved for future use
(I can delete this in the future, but I cannot insert a new section after the first comment)

 

[spinningmagnets]

reserved for future use
(I can delete this in the future, but I cannot insert a new section after the first comment)

 

[spinningmagnets]

OK, I am willing to pay $100 yankee dollars (paypal?) if someone can draw a plastic cell cap for me, and convert it to a file that a CAM service can make (plastic 3D printing). I'll publish the file here for anyone who wants to make these (although, its a horrible design, and nobody should want these).

It would connect one end of two cylindrical cells, two 18650's, and a second version for two 21700's (same design, slightly different dimension). The drawing below is my feeble attempt to show what I want. Similar to the square black plastic double-cell end-cap (shown, top right), but with a hexagonal shape. I will be paying with cash, not "exposure bucks".

 

[Triketech]

You mean something like this?

http://www.triketech.com/image/Drivetrain/18650_Hex_Top.PDF

 

[spinningmagnets]

Close, that drawing is halfway there. I have a few more details to add, then convert to a CAM file, and I'll pay you.

 

[Triketech]

Mark it up, send me a PM for email.

Not much to it.

They should be able to work with an STL file, most 3D printers do.

 

[Triketech]

FWIW

I'm working on a new battery mount. Prefer a commercially available battery.

 

[LewTwo]

I started my professional career as a draftsman on a 5 foot long wooden table pushing lead pencils across a sheet of vellum. I was trained to use Hogin CAD which was a 2D cad system running on a HP1000 mini computer via remote RS232 terminals. My first exposure to PC based cad was AutoCAD (Version 1.4 if memory serves) on a NCR DM5. That particular machine ran both CPM and MS-DOS operating systems.

My first major 3D project was using CADkey which was a PC based system. In that project we would work all week on the designs. Come the weekend we set up scripts to do the renderings on every available computer. Then we came in on Monday morning to see if we had anything we could actually use. By the time I left the industry we had moved to a combination of AutoCAD for 2D detail drawing and Solidworks for 3D designs.

These days I have a private perpetual license for BricsCAD but I have not upgraded since version 15.1 (due to cost). The newer version supports STL output. I chose BricsCAD because it has 3D capability but it uses the AutoCAD DWG format which is fairly Universal. More importantly it is one of the few CAD system that runs on Linux. I primarily use it in 2D mode but I did have a wild hair and drew up a battery pack design based on layers of plexiglass and brass sheets. The idea was to use brass screws that were threaded through brass (or Aluminum) bus plates to press on the ends of the cells. The slot down the middle was to accommodate the wiring. Ten bolts along the outside were to hold the assembly together. Ultimately I decided the design was too bulky and not worth the effort.

Modeling in 3D is a completely different concept from drawing/drafting in 2D. Many of us "old dogs" have trouble making the transition. It can also be a file management nightmare. Solidworks and other professional CAD systems have made much progress in this regard via tree based management and revision systems. However at the time I left the industry it was still a major pain in the most southern region.

FYI:
DraftCAD (which is free with one year registration) is a 2D DWG file based system. It is capable of 3D modeling but one has know how to use the 3D commands because they are not included in the menu system. It is a licensed version of ARES Commander by Grabert as is Corel CAD.

Reference: http://www.keywild.com/cad_library/KeyWild_Cad_Library_index.htm

 

[spinningmagnets]

I don't know how to mark up that drawing, but its a start. Below is a picture I just took of a styrofoam mock-up. Its double the actual size to make it easier to shape with a razor-blade. Rather than work through PM's, I'd like readers to see the process, in the hopes that readers with an idea would be encouraged to connect with other members with the skills to pull this off.



The cap covers one positive cell-end and and one negative end. There are radial channels on it in all directions. The central channel that runs the length is wider (8mm?) because it carries the high-amp series connection on a ribbon of nickel (or copper that is nickel-plated). On the styrofoam samples shown, the main lengthwise slot is cut out all the way to both ends, but I just realized it would be better for the rectangular series ribbon to be fenced-in on all sides, so the outermost surface should wrap all the way around both ends (I could post a pic if that would help?)

The other radial channels are smaller because they carry the paralleling current, which is less than an amp, and will likely be handled by small 24-ga wire.

Two features that are not on the styrofoam are axial slots at each point of the hexes. When the separate end caps are bundled together, those cylindrical slots form passageways for slender bolts to clamp the two ends of the cells together (I'll add another pic to illustrate). And I also need a way to keep the bundled end caps from shifting around in relation to each other. I decided to have radial holes on each hex face (a hole under each channel), and a short section of plastic rod would be inserted.



As a gesture of good faith, if you just draw that and post it, I'll pay you $50 now. For the full $100 I expect two STL files with all dimensions that I can hand to a 3D printer (one for an 18mm diameter cell, and one for 21mm).

edit: Here is a pic to highlight the main slot for carrying the series current (using a metal strip) and I added a tiny piece of styrofoam to refill the end-bumper that I had cut out, in my haste to make something to show.

 

[Triketech]

OK then.

I assume the caps for top and bottom at the same geometry.

I'll put something together today.

No worries about payment, you already do a lot for the community. But I'll need to knock it out before the middle of next week as I'm about to begin another design contract job.

• 8 mm Bussbar slots
• 2.5 mm Sense Wire slots

How tall? Current thickness is 5 mm.

• 12AWG wire has a 3.3² mm section, equal to 8 mm x .4 mm, say .5mm for Cupro-Nickel; assuming about 1-3 mm slot depth
• I would suggest at least 5mm solid section depth, with slot depth added to that depth; 6-8 mm total

If this is the direction let me know.

 

[Triketech]

I started my professional career as a draftsman on a 5 foot long wooden table pushing lead pencils across a sheet of vellum.

What a pleasure to know I'm not the only old fart here!

I still have a Bruning and a Universal Drafting Machines. In storage. Been a CAD user since 1983.

 

[spinningmagnets]

Thanks for the vote of confidence. Those dimension numbers sound good. Once a full set is 3D printed up and tested, there will likely be a V2, but that would entail additional payment for additional work. I'm not too concerned with the depth, it could be thicker rather than thinner, to add strength. The measurements you quoted is a good starting point.

One week is plenty of time for me to be happy with the result, no rush.

 

[tomjasz]

3D printer files would be SWEET!

 

[Triketech]

Here ya go:

18650 Hex Cap V2 PDF

18650 Hex Cap V2 STEP

18650 Hex Cap V2 STL

2.62 grams in Nylon.

ABS may have shrinkage issues.

Down the road you may return the favor.

 

[spinningmagnets]

Awesome, thanks! If you don't want cash, is there something else I might be able to do for you, as a token of my appreciation? PM me an address so I can mail things to you (doesn't have to be your home address, for privacy).

Would you like a resistance soldering rig? I am building one for myself, and I have two extra transformers I don't need.

If anyone wants to print up a set of these cell-caps and sell them, have at it. I hope you make a healthy profit. You owe me nothing.

...although, if you are making a profit from these, and we meet someday?...I would not turn down the offer of a beer.

In this pic, all of the series connections are made using common pure nickel 7mm wide strips, 0.20mm thick. If we are using cells that are rated for 10A, then each strip shown will provide 10A peak, for a pack total of 40A, in a 4P (four cells in parallel) configuration. It doesn't matter if this is a 10S (36V) or a 13S (48V) pack, the construction would be the same for 4P at 40A.

At this stage of the construction, the pack needs paralleling wires added, but they can be soldered to the nickel strips. The amount of amps carried by each wire is the max difference between two matched cells during charge and discharge. As long as the voltage in each cell is fairly close to its neighbor, the paralleling current would be less than 1/2 amp. There are several ways to attach them, such as being soldered or spot-welded (use solid wire for spot-welding, instead of stranded). By attaching them to the nickel strips halfway between the two connected cells, there is absolutely no danger of heat damage to any cell, regardless of the method used.

I know sometimes a new device can have its performance hindered if the committee designing it wants it to allow "all options". The beauty of open-source is that anyone can take this idea and optimize it for a specific design, by making a small tweak.

For rectangular "rank and file" shapes of battery packs, there already exists several kits for building a pack. I like the staggered "honeycomb" layout, because I think it is useful to use that for adding some type of air-flow fans. Of course, some existing honeycombed packs do not have an air-fan, so...you don't have to want fans to like the honeycomb layout.

As to options...should the builder use solder, spot-welding, or use resistance soldering? (a new thing around here). Choose the method you like, and please post the results.

Bus material...My research leads me to believe that...for 30A pack, there is nothing wrong with the common method of using 0.15mm thick nickel strips that are spot-welded onto the cell tips (at 4P, 30A would be 7.7A per cell, and per bus-strip) . But...when someone wants to use the full 30A of a 21700 cell, or maybe a pack of 15A 30Q cells (one of my top-2 favorites), nickel will get hot, no matter how thick you make it. The amount of wasted watts heating the nickel buses, and the voltage drop across the resistance of nickel buses...it may be small, but...some builders want to look at upgrade options, so why not?

I believe the series bus material should be copper or aluminum, either raw or nickel-plated. If you disagree, please build your pack to your desired spec, and post the results. If you are happy with it, I am happy for you. I am hoping this end cap design allows builders who use it to access all of these options listed above.

"Common pack design mistakes, how to avoid?"
https://endless-sphere.com/forums/viewtopic.php?f=14&t=84412

Honeycomb plastic cell grids already exist, but they are only for 18650 cells, no 21700 option, plus there is only one size of spacing, there is no option to increase spacing slightly for better air-flow.

 

[Triketech]

No worries about payment. Just keep up the good work helping others and others will help you.

For that matter do you have a packaging plan for the Hex Cap Battery; like a Top View array grid layout?

I could generate a profile of an array of Hex Caps to better visualize the routing of Bus Bars if that would help.

 

[sailah]

I use AutoDesk Inventor Pro 2018, I have a 3 year license. It's amazing what it is capable of. I came from a Rhino and AutoCAD background. I'll never go back. I also started hand drafting.

Inventor is crazy money but I've heard wonderful things about Fusion 360 as pretty awesome for what you get.

I also have a lot of experience with getting things laser and waterjetted from my DXF files. I used to be a waterjet instructor at the Pittsburgh TechShop.

For thinner stuff (which I'll call under 1/2" carbon steel) laser is going to be a cheaper option most of the time. Waterjet excels at difficult materials or nonferrous. I recently had some 1/2" 316 stainless plate cut for a fitting on my boat and laser was surprisingly affordable. I also thought the cut quality was excellent.

For work I have things laser cut often. Just recently had a batch of 250 special wrenches done.

I use a shop in MI and have had a great experience with them. They have laser, waterjet and EDM. You need to send them DXF files. But their prices are good and they are super fast. I don't know if I should be posting their info online, PM if you would like their contact info.

As I'm sure is obvious, 1 of something is going to be expensive, due to setup and pathing of the part. Always better to get as many as you think you can use or sell, the part cost goes way down.

I never buy material either, I always ask the shop to supply it. 100% the shop I use has it and can get a better deal than I can. And I buy 1000's of lbs of brass and stainless a week.

Here are a few recent projects for my boat, all from 316 stainless, TIG welded by me and after having them electropolished

 

[Addy]

For anyone who has some programming and/or math skills I would recommend OpenSCAD. It's very handy for making parametric designs that can be tweaked by just changing a few variable values. Right now I'm using it to generate a pulley for an HTD5 belt which will be strapped to my bike's rear wheel, but I don't have any pictures of that with me at the moment.

I've also used Autodesk Inventor (2015) which I was able to get for free as a student. It's very powerful and I've designed and 3D printed many parts with it.

 

[LewTwo]

Back in the day when people started building lead acid batteries with nominal 2 volt cell they somehow settled on 3 cells in series as a basic unit. Thus common lead acid batteries were made as 6 Volt (2x3=3S). These were placed in series to to create 6, 12, 18 and 24 volt supplies. Eventually they started producing most lead acid batteries in 12 Volt units. This were used in series to create 24, 36, 48, 72 and 96 volt supplies. Even 50 Volt telephone batteries were more commonly nominal 48 volts. The thing that remained constant was the multiples of 3 cells in series. Consistency is next to godliness and the single most critical factor in driving down cost in mass production. I do not think anyone builds a 10 volt Lead Acid battery.

When people started building lithium batteries with nominal 3.6 volt cells they tried to emulate the common voltage ranges for lead acid batteries. This was a particularly poor match for 12, 24 and 48 volt supplies. Thus we have batteries with 2S, 3S, 5S, 6S, 7S, 10S, 13S/14S, 20S and various others. There is no basic unit size. Consistency and standardization has gone straight out the window. I believe that the industry as a whole would benefit to settle on some kind of standard. Ebikes might best be served by a 5S basic unit but the power tool people would more likely prefer 3S. I realize I am just dreaming but I wish they would set a standard and start building components based on it. Eventually the savings would benefit everyone.

 

[spinningmagnets]

Eventually they started producing most lead acid batteries in 12 Volt units

Before WWII, it was common for the average car to have a 4-cylinder or sometimes an in-line 6-cylinder engine. All of them were low-compression (by today's standards). There had always been a pressure to raise volts, but choosing the exact voltage was like getting a bag of cats to agree on something. The availability of "Hi-Test ethyl" gasoline after WWII (the octane was average by todays standards), meant that higher compression ratios suddenly became a most-desired option when buying a car in the late 1940's. A few flatheads were still produced after WWII, but...the 1949 Cadillac/Oldsmobile light-weight high-compression V8's from GM were the milestone that were the tipping point to upping voltages.

When you needed to turn over the starter on the new high-compression engines at 6V, you could either double the size of the starter motor and the copper cables, or...you could double the volts. Too bad they didn't go straight to 48V (13 cells in series using lithium/ 13S), since lead-acid fully charged at 2.16V per cell is 51.84V when using 24S, and 60V is the thresh-hold for electricity penetrating dry skin.

 

[Triketech]

Battery Tech; its slowly moving quickly forward.

Li-Ion technology is beginning to reach the density/discharge barrier. There are a few other chemistries that show great promise for the next gen, and it looks like Lithium Sulfur is maturing; still about a few years away from e-bikes. I've worked with these folks on a machine design project. They project 2-3 years. 4X power density, at similar discharge rates.

http://www.sionpower.com/

Some of the automotive industry has been considering a move to either 42V J2622 SEA standard while Mercedes and BMW are looking at 120V systems. This shift enables powering AC compressors and other auxiliary crank driven units including superchargers that draw lots of watts. Mercedes has a pretty cool induction flywheel system that works two ways; generates power or provides a 30 KW boost at low speeds - mostly to compensate turbo lag from idle.

The aircraft industry has been moving up from 28VDC for weight savings. Take the new Bombardier business jet (still 28VDC) which has over 110 lbs of wiring just for 28VDC. Increasing voltage to 200 VDC cuts 60 lbs. This from an industry who spends a fortune to cut grams from every component.

 

[LewTwo]

For anyone who has some programming and/or math skills I would recommend OpenSCAD. It's very handy for making parametric designs that can be tweaked by just changing a few variable values. Right now I'm using it to generate a pulley for an HTD5 belt which will be strapped to my bike's rear wheel, but I don't have any pictures of that with me at the moment.

I've also used Autodesk Inventor (2015) which I was able to get for free as a student. It's very powerful and I've designed and 3D printed many parts with it.

Well that got me curious so I installed OpenSCAD. It really reminds me of the way we used CadKey three decades ago. There are some major differences though. Cadkey could produce dimension drawings and output valid DWG files. OpenSCAD can only output DXF files of 2D entries. So you are left with a bit of a conundrum if you need actual working files for anything other than 3D STL printing. To be fair I should mention that we paid THOUSANDS of circa 1980 dollars per seat for CadKEY. The really disappointing thing was that I could not load the STL file provided by Triketech

Then I ran across "FreeCAD" and looked at some of its import/export options. Among these were DXF, SCAD, STEP and STL. So I decide to try it as well. By the way I am running Linux Mint. The 'Stable' version included with the distribution crashed my computer. I had to resort to using the launchpad PPA to get a later version that seems to run fine (0.16). That was also NOT able to load the STL file ... however it was very happy with the STEP file. Then I exported that as a SCAD file that would load into OpenSCAD but with errors. After a bit of fiddling I managed to get OpenSCAD to produce a STL file ... that it also failed to load.

Ultimately I redrew the file in OpenSCAD (it has a very short learning curve). I then imported that into freeCAD and exported it to DXF (plan view this time) that I could import into BricsCAD to check the dimensions. Good thing that I did that .. there was a sizing error I could have never have found in OpenSCAD. That error has been corrected.

I quite like the OpenSCAD concept but I have place it in the "not ready for prime time" category. It may be suitable if one's need are limited to producing STL files for 3D printing.

FreeCAD on the other hand looks very interesting but I suspect it has a MUCH steeper learning curve. It also has a command line window available (Python console). Its major shortfall is the inability to work with 3D DWG/DXF files. This is one that deserves a bit closer look.

Now for all you Boys and Girls that might want to play with either the applications or the files I have attached a zip file
If Spiingmagnets and Triketech have no objections I would like to declare these files to be "PUBLIC DOMAIN":
View attachment 18650_Hex_Top_V2 files.zip