View Full Version : How to make a motor mount

08 November 2013, 2020
Lot of people have posted their motor mounts and some description of how to make one. I want to start a thread on how I made the mounts for my KZE (http://www.elmoto.net/showthread.php?2003-82-KZ550-the-KZE) in every detail. Every bike is different, but hopefully there will be enough detail here for people to repeat the basic steps with their own bike.

I'll be adding new posts every few days, as I have time. Please add comments and suggestions, but I want to keep this a pretty clean "how to" thread.

Before we get started - take a deep breath. You can do this.

Without further ado...

08 November 2013, 2027
I'm going to assume you've already stripped the frame of your donor bike. Just get all the ICE (internal combustion engine) guts out. It really helps to have a stand of some sort. I'm using a hydraulic motorcycle lift.

Here's the frame from my '82 KZ-550. There are 8 mount points for the original engine, and 2 holes for the swingarm pivot.* I'm going to use the engine mount points toward the back to mount the electric motor. Ultimately I'll use the 3 on the left side of the frame, plus the lower one on the right. The 2 engine mount points toward the front will be used to mount my battery pack.


*There were originally 10 engine mount points. I already took an angle grinder to the front two.

08 November 2013, 2035
Some more introductory info. I'll be installing a Motenergy ME1003 (http://www.motenergy.com/me1003.html) in this bike. It's a hugely popular conversion motor, and for good reason.

It has what's called a NEMA C-face (http://www.grainger.com/tps/motors_nema_motor_dimensional_chart.pdf) mount. It's a type of bolt pattern that is used on a lot of motors. It corresponds to the 4 outermost bolt holes on the front of the motor. On this motor the bolt holes are 3/8-16 tap, 3/4" (19mm) deep, 5.875" (149.2mm) bolt circle. There is a raised circle in the center that's 4.5" (114.3 mm) diameter, 1/8" (3.2mm) high. Those measurements will all become important later on.

(Those measurements are the same on other Motenergy motors, as well as many 6.7" series and AC motors.)

The ME1003 will have the axle pointing toward the left side of the bike, since the KZ has the chain on the left.


Here's where we're going eventually. (Ignore the rusty frame please...that has since been taken care of.)


08 November 2013, 2044

An alternative to some of the methods here are PAD, which Ted does a nice job explaining in this thread (https://www.elmoto.net/showthread.php?3358-How-to-PAD-(making-parts-to-fit-other-parts-using-Photoshop)).

If you want to do Skethup PAD, that's here (https://www.elmoto.net/showthread.php?3359-How-to-SPAD-(Sketchup-Photo-Aided-Design)).

09 November 2013, 0817
I love the Motoenergy motors. My 2012 Zero that has gone 50,000 miles has one.

So it's a great motor to use for starting a build and a great choice for this thread Noah! The Zero uses almost the same motor. The ME0913 with a little better cooling.

Lol most motor pictures don't have such a good photo like the one above, but I remember that one for sure. A guy that used to post on this forum a lot a year or so ago when I last spent a lot of time here took that.


His name is Ted Dillard. Really active in the Electric motorcycle world, and author of a book on how to build them. If you get a chance, give Ted a shot out, and a big thanks for that photo, he's one of the biggest contributors to the world of electric motorcycling in so many ways. We all owe him a lot of thanks.

I spoke with him not too long ago about a trip I'm taking and this morning there were links in my inbox to an article he wrote about it.


Thanks Ted. You da man!

09 November 2013, 1137
Apologies to Ted for using his pic. I got it from here (http://evmotorcycle.blogspot.com/2012/04/motor-and-controller-are-ordered.html). It looked like a stock photo, so I didn't think anything of it. I picked it because it was nicely shot at just the right angle - figures Ted took it. I replaced it with my own pic, just so I don't step on any toes.

09 November 2013, 2347
The first thing I'm going to do is measure the bolt holes. I'm using a pair of digital calipers. If you have the original engine bolts, you can measure them. A plain old ruler also works, I just find calipers easier for measuring inside diameters. If you do use a ruler, try and get a metal one with clear markings. Wood and plastic ones don't belong in a shop (IMO).

This bike is metric, so I'm doing everything in millimeters (mm). You can see the calipers read 10.93mm. I'm going to call that 11, because it's close enough, and I get to say my bolt holes go to 11.

This is actually over sized to give some wiggle room. The bolts are 10mm. That's why a ruler will work fine. Above 6mm, metric bolts and screws come in 2mm increments.* So, I know that an 11mm hole takes a 10mm bolt.


*Below 6mm, there are 1mm increments. Sometimes you see the term screw, sometimes bolt. There is a technical difference, but it doesn't really matter unless you're talking about self-tapping screws, which I'm not. I'll be using screws as bolts and bolts as screws. If you really care, read this (http://engineerexplains.com/answr/Screw-vs-Bolt1.html) or this (http://en.wikipedia.org/wiki/Screw#Differentiation_between_bolt_and_screw).

10 November 2013, 0000
I draw up a diagram of the bolt holes to keep track of everything. The upper two holes are both 9mm, which means an 8mm bolt. I should say here that an 8mm bolt is called "M8", and the standard thread is M8x1.25.*

I'm going to fill in the dimensions later. I've drawn a front view at the bottom. It has the two lower mount points, and the left side of the frame (which is on the right looking from the front). I'm not going to use the right side engine mounts. Since the bottom mount points are offset we'll have to figure out how to measure that. Coming up soon.


*Fine thread is M8x1.0. You won't find those very often. BUT - sometimes you will see fine thread on bikes. Especially M10x1.25 that are used on triple clamps, among other things. I like to use stainless hardware, and I've found 2 places in the world that sell M10x1.25 stainless socket cap screws...for $6 each. Price of fashion.

Ken Will
10 November 2013, 0758
There is a technical difference, . If you really care, read this (http://engineerexplains.com/answr/Screw-vs-Bolt1.html).

The definition in the link is absolutely wrong!! The difference between a bolt and a screw is the head, not the shaft.
You insert a male tool into the head of a female screw. A female tool wraps around the male head of a bolt.

An Allen wrench is actually a bent screw driver.

10 November 2013, 0911
Ah - then "screw you" makes a lot more sense... :)

There is so much terminology. An Allen head fastener is often called a socket cap screw, but a socket is the tool you use to drive a bolt. I guess because the allen wrench goes inside the socket cap, and the bolt goes inside the socket wrench? Sigh...

Anyway, motor mounts...

10 November 2013, 1039
OK, time to measure some distances. Seems easy enough. I've done this enough to know that unless you have some crazy laser scanner, you'll need to fix up your dimensions later on. This is just to get as close as possible until the next step.

First I measure the distance across the bottom holes. Even though my ruler starts at zero, I don't trust it. I measure starting at at 30mm mark and see the other side is at 191mm. Distance between the tabs is 161mm. Write that down.

I used my calipers to measure the tab thickness: 4.5mm. Write that down too.


Next I measure the top holes. I'm using the 10mm mark and measuring from the sides of each hole. I get 10,19 for one hole, 59,68 for the other. Good, the holes were 9mm so that tells me I was measuring roughly in the center. I just subtract 59-10 and get 49mm for the center-to-center distance.


10 November 2013, 1043
The next one is where it gets tricky. The tabs are offset from the upper holes. So I put the original 10mm engine bolt through the holes so that it sticks out the side. Now I can measure to the bolt. I'm careful not to tip the bolt in the holes, just let it rest gently on the bottom.

I measure from the top of the bolt to the bottom upper hole. This time I'm just using the end of the ruler, even though I know it will be off a bit. This measurement will get fixed later on. I get 161,170mm to the two sides of the upper hole.


Now, the holes are 11mm diameter and the bolt is 10mm, sitting at the bottom. That means to figure out the center-to-center distance I have to draw a picture. Here are the measurements I have so far:


OK - get ready for a little complicated reasoning. See the little drawing on the right with two circles? The outer circle is the hole (11mm), the inner circle is the bolt (10mm). There is a 1mm gap at the top since the bolt is sitting at the bottom. That means I'm measuring 1mm from the top of the hole. It's 11mm diameter, so 5.5mm radius, and I've already taken up the first 1mm. There are 4.5mm remaining to the center of the hole.

The measurements I took were 161 and 170mm. The mid point is 165.5, half way in between. So take that, add the 4.5mm I just figure out, and you have 170mm from center-to-center.

Sorry if that seems complicated. Go over it a few times and hopefully it will make sense. Or maybe there is a clever way to make it simpler, I just haven't thought of one because this works for me.

10 November 2013, 1354
The next thing I need to figure out is exactly where the three holes are relative to each other. There are two ways to do it. One requires uses a nifty little tool, the other uses math.

The tool way: What we want to get is the angle between the top two holes and the bottom holes. I'm going to use a protractor - like the one you had in 5th grade, except it has a pivoting arm that helps you take the measurement.

I put M8 bolts (screws?) through the upper to holes and secure them with nuts. I try to get them pretty well centered in the holes before tightening them down. Then I put a straight edge across the bolt through the bottom holes one of the top bolts, and hold it in place with a clamp. Put the protractor against the straight edge, and adjust it to measure the angle along the top bolts. Now I just pull the protractor off and read the angle - 147 deg.

Since the top bolts are 8mm and the bottom is 10mm, the angle isn't quite right. But that error is smaller than what the protractor is capable of measuring anyway. You're probably getting the idea, none of this is going to come out perfectly on the first round.


The math way: measure the distance from the bottom hole to the top hole. I did that and got 211.5mm center-to-center. So now I have three sides of a triangle: 49, 170, and 202.5mm. Now use this thing called the "law of cosines (http://en.wikipedia.org/wiki/Law_of_cosines)". Don't worry, you just put in the numbers and crank out the angle.

I want the angle between the 49 and 170mm sides. To get that:

angle = arccos[(49^2 + 170^2 -211.5^2) / (2*48*170)] = 145.4 deg

About 1.5 deg off from the protractor measurement. But less than 1% different, so I'm happy. It's a good check that the "true" angle is somewhere around 145-147 deg.

(If all the math worries you, the protractor is only about $12. Just buy one - you'll use it over and over.)

10 November 2013, 1434
Here's the last measurement I need to make. It's the offset between the upper holes and the lower tab. I clamp a straight edge to the plate with the upper holes. Turns out I got lucky and they're perfectly vertical with a flat surface.

Then I use the bolt on the bottom to keep things square and measure over from the tab. I know this measurement is going to be off and I'll have to fix it, so I'm just using the ruler end. I get 58mm.


10 November 2013, 1438
So there we go. I've got all the measurements I need. I've drawn it on my little sheet of paper. The next thing I'll do is draw it up in CAD.


11 November 2013, 0751
...or - you can use the magic of photon capture as Ted does here: http://evmc2.wordpress.com/2013/11/11/how-to-pad-photoshop-aided-design-tutorial/

No matter which technique you use, I find it helpful to cut pieces out of cardboard or louan plywood to make sure I haven't made any serious boo-boos. :)

11 November 2013, 0831
PAD is a great technique, and Ted's tutorial is really helpful. A nice addition to the knowledge base. I've done that using my mid-grade digital camera. You have to get the shot just right - if you're off center or too close it distorts the measurements. (Ted is a pro photographer, so he can make this stuff work...and he knows what "parallax" is.)

Either way you go, the next step is to get it drawn up, either by you or someone else. Then as Frank says, make a mock up out of cardboard, wood, or plastic and check for fit. That's where I'm going next.
__________________________________________________ _______________

You could, at this point, just stop and hand what you have to a machine shop. They'd still need to make a mock up so you could check your measurements (unless you're very sure of yourself - but considering what materials and labor cost, I like to be sure - especially when you're trying to align more than 2 holes that aren't in the same plane).

The next section is if you're going to make your own mock up. After that I'll go to fabrication. You could stop at any point you think you've reached the limits of your ability (or tools). I didn't know how to do this before, but I wanted to learn and do it myself because it was fun. Where the fun stops is totally up to you.

11 November 2013, 0848
If you or a friend are good at drafting, you could use these measurements to make a to-scale drawing by hand. Or just go straight to a mock up.

Or you can use software to do CAD. I use Sketchup (http://www.sketchup.com/). It's free, and relatively easy to learn (compared to other CAD software).

I'm going to make a drawing, print it out, and put it on cardboard to check for fit. Here's the Sketchup drawing.

You'll notice that I'm using a tall, narrow window. That's because of how Sketchup handles printing to-scale, which I'll do next.


11 November 2013, 0854
To print the drawing to-scale, you have to wrestle with Sketchup a bit. Position the drawing like I did in the last post. Now go to "File > Print Preview". Uncheck "Fit to Page" and "Use Model Extents". Set the "Scale" to 1-1, as shown below. This makes the printout the same dimensions as the drawing.

If you're lucky, your drawing is small enough to fit on one page. That's why I made a tall narrow window. Sketchup tries to print the area you have in the actual window (unlike any other software I've ever used). If it doesn't fit, Sketchup will print multiple pages and you have to cut and paste them together.

Click OK and make sure it will print the way you want. I have my print with the holes over to the right. If it looks good, print for real.


14 November 2013, 1529
Hey Noah,

What gives I can no longer see your pictures?

14 November 2013, 1549
Hey Noah,

What gives I can no longer see your pictures?

Not sure - I can still see them. Anyone else not see them?

14 November 2013, 1645
Not sure - I can still see them. Anyone else not see them?

They look good to me.

15 November 2013, 2326
No, mate. There are no pics too see.

Elmoto, you have admin so it might be a permission thing.

Ken Will
16 November 2013, 0513
I can see them fine.... with Mozilla Firefox.

16 November 2013, 0942
I can see them in Tapatalk.

16 November 2013, 1011
fine on mac and Android with Chrome browser

16 November 2013, 1730
Let's clarify. What was the last pic that's claimed not to be seen?

I'm seeing up until the software screenshot.

I'm current using Android Lastpass browser.

17 November 2013, 1029
Not sure what to do about the pics issue, sorry if you can't see them.

I printed out the Sketchup drawing and glued it to a piece of cardboard. I punched out the holes - this just makes it easier for me to see how well it fits. The top holes are spot on, so I line them up and clamp the cardboard to the frame.


The lower hole is off by a few mm. Not unexpected, and why I'm doing the cardboard fit now. I use the long engine bolt to get the alignment and mark where the hole should be on my cardboard mock up. I'm trying to hit the center of the bolt as accurately as possible, but I know it will still be off a hair. Two things will save me - one is that all the holes will have some wiggle room. The other is that I'm going to do the cardboard fit again once I've adjusted the hole positions, which will get me pretty well spot on.

I just measure from my marks over to the lines on the paper marking the original hole center, then make the adjustment in Sketchup.


17 November 2013, 1117
New hole drawing printed out, fits like a glove. All the bolts fit with some wiggle room, which is what I want.


17 November 2013, 1123
While I've got the cardboard up there, I mark the swingarm line. I'll need this later to figure out where to put the motor shaft.

I just lay a straight edge along the top of the swingarm and draw a line on the paper. It works with this bike, might have to do something different if your swingarm isn't a nice straight line. Since this is the TOP of the swingarm, I need to move the line down by half of the swingarm thickness. The idea is that you want a line that goes through the rear axle and the swingarm pivot. The motor shaft will sit just slightly lower than that line (more on that later).


17 November 2013, 1133
I also traced the curve of the frame on my mock up. Now I have a template. I stuck it in my scanner (just the one in my $85 printer). The cool thing about this is that since the template fits inside the scanner bed, the scan I get is actual size. I can import the image into Sketchup and use it to start designing the actual motor mount.


17 November 2013, 1203
Now that I made a template, I started thinking - couldn't I have just stuck a piece of cardboard up there and marked the holes? Yes, but you still have to go through the process of taking measurements (unless you plan to just hand a machine shop a piece of cardboard with circles on it). I've figured out that in the end it saves time to measure, mock up, check, then adjust. If you go straight to cardboard you end up having to measure and adjust things anyway.

That said, there's no one right way to do this. You could do PAD (http://evmc2.wordpress.com/2013/11/11/how-to-pad-photoshop-aided-design-tutorial/) (photoshop aided design) too. I've used different techniques, and it comes down to what works for you, and what works for the particular part you're making. The one rule that I follow no matter what is to make a series of mock ups before going to the final product. There is no method that will guarantee you a perfect fit without checking it (unless the part is really simple, you just get lucky..or have some crazy 3D scanner).

Just so you know where we're going:

Next I'm going to design the mount in C(omputer)AD. Then I'll do C(ardboard)AD again. Once I'm happy with that, I'll make a plastic version. Plastic is cheap, machines really quickly, and it's strong enough to actually mount the motor and check everything - not just whether the holes line up, but also whether the motor fits where you put it, doesn't hit anything, the chain lines up, etc. I use HDPE (http://en.wikipedia.org/wiki/High-density_polyethylene), aka plastic cutting board - literally. About $12 from Target, and you usually have enough plastic to make two mounts.

You also have to remember that the battery and other things are going in there. It's not a bad idea to do everything in cardboard and plastic, and do the metal version when you've got everything sorted out. (But this isn't a whole bike thread, just motor mount, so I'll assume it's going to work out perfectly...)

17 November 2013, 1931
Time to put the ME1003 into the drawing. The main things I need are the outer diameter, the bolt holes, and the power terminals. The shaft is positioned just below the swingarm line (so that when the rear suspension sags the chain lines up). The motor is positioned so it fits just forward of the wavy line I drew of the frame.

The tricky part is getting the terminals positioned. They can't go forward because my battery will be there. They also can't hit the frame or the swingarm pivot. The rotation shown in the picture works...except for one thing. The rightmost bolt of the motor might get in the way of the chain. Since I pretty much have to use this rotation, I'll have to deal with that bolt...later.


17 November 2013, 1942
After some more work, I end up with this. There is one extra hole at the bottom. That's for a brace that helps keep the motor from twisting the mount sideways under load (more on that later*). You can see the brace in the pic in post #3 (https://www.elmoto.net/showthread.php?3263-How-to-make-a-motor-mount&p=41343&viewfull=1#post41343).


*I keep saying I'm going to talk about things later. I'm telling a pretty linear story of something that was very non-linear, that I figured out as I was doing it. The first mount I made for this bike didn't have a brace, and I immediately realized it wasn't going to be strong enough, so I redesigned it. I've had a lot of practice making motor mounts that I didn't use.

17 November 2013, 2029
I'm not a professional machinist. The method I use works really well with the CNC milling machine I use. It's programmed using vertices, so that's what I dimension in the drawing. Sketchup makes this fairly easy to do. You use the "Text Label" tool. If you click on a vertex it will automatically fill in the coordinates. I've marked every vertex that needs to be programmed into the CNC, plus radii and such.

I also designed in recesses. They save a tiny bit of weight, but honestly I just did it because it looks cool (IMO). If you want to keep it simple, you can skip the recesses and all the fancy curves. I like designing and machining parts, so all the fancy stuff is just more fun.

If you don't have access to a CNC, you can still do quite a bit with a manual milling machine. If you don't have that, then a jigsaw and a drill press can do the job. There's a lot to be said for ingenuity (but now that I have access to a CNC I'm completely spoiled.)

(A larger version of this image is here (http://www.colorado.edu/physics/EducationIssues/podolefsky/EV_project/KZE%20Mount/motor_mount_kze_ME_4_coords.png).)


18 November 2013, 0612
very clean mount Noah, it should be in production to purchase publicly - its amazing that Montenergy hasn't produced a motor mount to sell with their products...

awesome Thread and Thank You Noah :)

18 November 2013, 0915
Thanks Allen!

29 November 2013, 1104
I have searched high and low and can't find the plastic mockup I made. So I'm going to skip a bunch of steps going from drawing to plastic mockup to final piece. Just have to imagine turning this:


into this:


It has what's called a "contrast cut". First you machine the part without the recesses. Then paint, then go back and machine out the recesses to reveal the contrasting metal.

29 November 2013, 1111
While I was trying to find a nice example of a wood or plastic mockup, I found this guy's blog. The '81 KZ750 is really similar to the '82 KZ550 I'm using here. It's a different approach than I'm taking, a nice alternative approach to basically the same bike.


29 November 2013, 1123
You'll notice three things in this write up, and in the blog post above.

1. The mount points on the KZ frames are offset.
2. You need to get the motor in the right position to align the chain.
3. The mount needs to be braced against twisting under load.

These are true on just about any bike. My GSX-R frame is a little easier on #1 - the original mount points are (almost) perfectly aligned - the offset is accomodated with a small recess cut into the mount plate. On the KZ, I need to make a spacer from the upper frame mount points over to the main mount plate.

Chain alignment is made simpler due to the fact that the shaft on the ME1003 is a couple inches long, so I can move the front sprocket back and forth. So, I have to make sure the motor sits in such a way that the shaft is in the right spot. Luckily, the bottom engine mounts are in just the right place so that I can stick the mount plate there and the shaft will line up.

(If it didn't work out, I'd need to make spacers or find some other way to get the motor over to the left or right.)

To stop twisting, I added a cross brace that uses the other bottom engine mount.

Here is a drawing of the whole assmbly, including the upper spacer and the bottom brace. I won't go into it here, but I went through the same process of drawing these these pieces, mocking them up, then checking for fit before making the final pieces in aluminum.


29 November 2013, 1136
Here are the 3 final pieces. If you look closely, you can see that where the bottom brace bolts to the main plate, it sticks out a little. This creates a little gap so the brace and the plate sandwich the lower engine mount.

(The brace gets painted all black - since it's under the motor, I didn't go through the effort of contrast cutting it.)


And finally assembled and mounted in the (previously rusty) frame:


10 December 2013, 1931
Following up on one of the things I said I'd explain later...

Because of the way the motor needed to be angled, the bolts could get in the way of the chain. I used low head cap screws and cut in countersinks so they sit flush. See what I mean in the pic below:


Getting the chain line right is made easier by the fact that you can move the sprocket back and forth on the shaft. However, I don't trust the set screws that are in most plain bore sprockets, even with thread lock. So, I use shaft collars on each side of the sprocket (with the shaft key sandwiched in between). I use single screw, aluminum ones like in the pic below. They take up room on the motor shaft, which means less side leeway for chain alignment - so if you go this route (and I high recommend you do), you need to design the mount so the sprocket lines up with the collars installed.


10 December 2013, 1940
After I got all this done, someone asked if I was worried about getting my pants caught in the chain. Good point...back to the machine shop.

On my GSX-R, the original chain guard fits on the motor mount. On the KZ, no such luck, so I made my own. I decided to make a project out of it and put my Flux logo on it. (Flux motorcycles isn't really anything...yet...just a place holder in case I get something to take off some day.)

The chain guard was made from a solid block of aluminum (what they call "billet", which means it was machined from a single piece rather than cast). Here's the whole assembly:


21 December 2013, 1616

I think this is such a great thread for el moto, and you've done a great job. Do you have any recommendations or vague guidelines for new folks as far as motor mount thickness and material goes?

I am assuming that a lot of people don't have solidworks, and obviously won't be running stress tests and other simulations.

21 December 2013, 1922
Glad to do it!

I'd recommend 6061 aluminum alloy - strong and easy to machine. The last two mounts I made were milled down to 10mm thick, about 3/8". That seems like enough if there is bracing to prevent sideways bending. If you don't have as much sideways support, you could go up to 1/2" thick. Without stress tests it's better to error on the safe side...the weight penalty is very small.

If you're using steel, 1/4" should be fine.