Making inline motor brackets

Share your build process step by step
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1. Pictures of your starting materials. Choice of body, Chassis type and material (brass, plastic etc.)
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Making inline motor brackets

Postby gascarnut » Mon Feb 27, 2017 9:25 am

In my previous thread here, where I built the Porsche 904 GTS for BrumosRSR, I promised to provide some details about how I make the motor brackets I use, so here it is!

First off, materials:

I use .040” thick brass for my brackets, as I like the extra strength and the little bit of extra weight that this thickness provides in comparison to the .032’ material that most commercial brackets are made from. I buy scrap pieces from the “Project Bin” at a company called Industrial Metal Supply - they are conveniently located a short drive from my house, and they also have a very well-stocked K&S metal selection, so most of my building materials are bought there.

I cut strips of brass ½” wide off these scraps, using my band saw. It has an 18TPI blade so it rips through the brass pretty easily.

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What I’m looking for at the end of this is a number of pieces all ½” wide and a little bit over 2” long. I don’t try to cut too close to the 2” limit on the band saw, I leave a little extra always. You will see why soon.

I also don’t usually make one bracket at a time, the process is quite long and it makes sense to make a bunch at once. Plus, since it’s such a manual process, they don’t all come out right!

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So now I have the blanks, it’s time for some more precision work. I use a belt sander to smooth the long edges on the strips, then I go to the disc sander to finish the length. After a lot of experimenting, I have worked out settings on my bending brake that will give me a 3/4” wide bracket from a 2” long strip, so the closer the strips are to that measurement, the more consistent the bracket widths will be. Also, it is important that the ends of the strip are very square to the long edges so that the brackets when bent are nicely flat and square.

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Now it’s time to mark the dimensions. I “blued” one of the strips so the markings come out clearly on a photo, but generally I just scribe them onto the plain brass with the sharp edge of my digital calipers. Here’s the drawing and the item:

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You’ll notice there’s a double mark on the center hole. I always mark that one from both edges of the bracket to be sure that I have the motor perfectly centered. When I center punch the hole, I estimate the spot between the two lines.

You will also notice that in the drawing for this batch of brackets, the axle holes are on a different center line to the motor holes. These brackets are destined for 1/24 scale Retro cars, where we run 13/16 rear tires and a .050" clearance, so the offset between the axle and the motor holes allows the bracket and motor to sit flat in the frame. The gears we use accommodate this without issue. Obviously it is just as easy to make brackets with no offset or a different offset, like the .040" that would be used for the Slot.it offset gears.

Continued in the next post.
Last edited by gascarnut on Mon Feb 27, 2017 10:01 am, edited 4 times in total.
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Re: Making inline motor brackets

Postby HomeRacingWorld » Mon Feb 27, 2017 9:27 am

Priceless information here boys.

Thank you for taking this time and effort.
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Re: Making inline motor brackets

Postby Z-carfan » Mon Feb 27, 2017 9:33 am

OH yes, this is the stuff right here! I look forward to the follow up.
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Re: Making inline motor brackets

Postby gascarnut » Mon Feb 27, 2017 9:34 am

Thanks, Harry!

Onward:

So, once the strips are all marked up, I center punch each hole position. I use a pair of “Geezer goggles” (Magnifiers) to be sure I get the punch mark exactly right. You can use a regular center punch and a small hammer or one of those self-activating punches, but I prefer the hammer, as the first tap on the punch is a very light one to be sure I am right on the cross-hairs of the markings. Then if I am, I can hit a bit harder the second time to deepen the mark. If not, then it is easier to relocate the punch slightly and re-hit it to get the mark centered. My punch is actually an old diesel engine fuel injector pin that was precision ground to a point for me by a friend with a machine shop. It has lasted me 20+ years without needing sharpened, that’s how hard those injector pins are!

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OK, so that sets everything up for punching the holes. I use a hand punch from Micro Mark that is mounted in a Roper-Whitney mounting bracket. You can probably find good Roper Whitney punches on eBay, they are probably better quality even when used, but this one works fine. You will need a few sizes of punch pins and dies, 3/32” for the motor mounting screw holes, 3/16” or 7/32” for the axle bearing holes, depending on whether you want to mount the bearings directly in the bracket (3/16) or in some 3/16” tubing that will fit into a 7/32” hole in the bracket. Some folk might use other sizes, the Micro Mark punch has 3/32 to ¼” in 1/32 increments as part of the set.

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The punch pins have a small dimple on the face of the pin that will locate in the punch mark on the bracket strip and helps to locate the hole properly. You develop a “feel” for it after a while, lowering the punch pin down, feeling it locate in the center punch mark, then squeezing the punch to pierce the hole.

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OK, here we have to stop and remind ourselves what our fathers told us: “Measure twice, cut once”!

As you can see, I forgot to check the size of the punch pin that was in the punch, so the first hole was punched at 1/8” diameter instead of 3/32” That’s why there is a second strip in the photo now! (Remember what I said about cutting a whole bunch of strips?)

Once all the motor holes are punched, swap out the punch pin and die for the 3/16” or 7/32” size to punch the axle holes and the motor hole. I used the 3/16” punch for these brackets, as I want to mount bearing directly in the brackets.

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You can see I could probably still use the blued bracket, a screw with a washer will work.

I punched the motor hole with the 3/16 punch, but it has to be opened up further, as the motor housings are 6mm in diameter. So I drill these out with a 6mm drill. You generally will not find metric drills in US Hardware stores, so you may have to rely on MicroMark or McMaster-Carr for one, although I think I have seen some nowadays in OSH here in SoCal.

Remember to always clamp brass when drilling, drills have a tendency to “grab” thin brass plate and create “brass propellers” that can inflict injuries (You can ask how I know, but realize that the answer might involve photographs of scars!). :oops:

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Re: Making inline motor brackets

Postby gascarnut » Mon Feb 27, 2017 9:43 am

Episode 3:

Now to the bending. I have another handy MicroMark product for this:

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The top half of this handy device is a shear that can cope with up to 1/16” thick brass if it is not too wide (about ½” maximum). The lower half interests us today, it is the bending brake, with an adjustable stop.

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Over the years I have been making these brackets, I have empirically developed a position for the stop that yields a ¾” wide bracket from a 2” long piece of brass. I have a little spacer that I place between the stops and the bending die to set this. No photo, but I mention it for a reason. Stay with me for that!

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I slide the flat strip into the brake with the short edge up against the stop, and wiggle it a little to ensure I have the end completely flat on the stop (remember earlier how I stressed the importance of the ends being square – this is why). Then close the bending die down onto the strip and squeeze until significant resistance is felt.

I should point out here that I always place the punched strip in the bending brake with the entry side of the punched holes downward. This gives me the nice, slightly rounded edge of the holes on the outside faces ot the bracket. It's not a big deal, especially when the punch pins are new, but as they wear there is a more noticeable rounding to the one side of each punched hole.

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This should give close to a 90 degree bend:

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Turn the strip around, feed the other side into the brake and from the second bend:

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Now, remember the story about measuring twice, and the story about the little spacer for setting the bend distance? Guess who forgot to check that spacing! The stop had moved slightly and this bracket came out way too narrow, so I had to re-set the stop before I bent any more, and therefore from here on, the little “blued” bracket no longer has a role in this story! Oh, well – live and learn (I wish…) :oops: :oops:
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Re: Making inline motor brackets

Postby gascarnut » Mon Feb 27, 2017 9:51 am

Episode 4:

Once all the other blanks were formed correctly, I continued to the final steps of checking and adjusting. As hard as I try to get these all square and flat every time, I am not always 100% successful, and in any case the process itself introduces little deviations that need correcting. The tools now are pliers and files and a horribly rusty old engineer’s square that has spent too much of its life too close to acid flux!

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Sometimes the two “legs of the bracket are not exactly parallel after bending, as seen by the light showing under the end of this one:

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I grab the motor face in a pair of pliers and tweak the offending leg a little until the bottom faces of the bracket all sit flat on my building jig.

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Then I focus on the motor mounting face. It is important in my opinion to be sure that the face where the motor will mount is completely flat, as one does not want to risk deforming the motor of the bracket when screwing the motor in, as this could cause friction in the moving parts later on. So, I place the bracket over an index finger and draw file the mounting face.

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As you can see, the punching and bending have deformed the surface somewhat, so it needs to be filed until the file marks spread across at least all of the area where the motor will touch:

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This one is fine, that little bit at the bottom won’t make any difference.

You can see that I have also rounded off the top rear corners of the bracket. Sometimes I do that while the strips are still flat:

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But most times I wait until the forming is done, as a square end makes the marking of the hole positions easier and the bending process a bit more accurate. At this point in the process, either a flat file or the belt sander can be used, I generally just round them off with a flat file.

Once the mounting face is filed flat, then use a square to ensure that the legs are nicely at 90 degrees to the mounting face. Hold the face in a good pair of pliers and tweak the legs as needed.

If weight is not a prime concern, then the brackets can be used like this. However sometimes it is nice to lose a little bit of high-up weight, so I mark a section and trim it out of the motor mounting face:

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The nifty tool for this is a nibbler, but I guess it could be done with a small hacksaw and file as well. After the majority of the material is nibbled away, I clean up the edges with a flat file again. This cut-out is advantageous when the motor has a pinion that is bigger than 6mm, not that this happens often with 1/32 scale inline cars, but on the 1/24 Retro cars it does. The cutout allows the motor to be removed without having to remove the pinion.

So that’s it, a nice little inline bracket. Or in my case, a whole lot of nice little inline brackets:

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Altogether, with the time taken for photographing (and measuring twice!), this batch took about two hours to make. Yes, I guess I could buy them from JK or elsewhere, but to me, this is part of the fun of scratchbuilding, and has fueled my obsession with tools too! I just have to have the tools!

I hope this was instructive and enjoyable.

Dennis
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Re: Making inline motor brackets

Postby nhdungeonracer » Mon Feb 27, 2017 10:52 am

Thanks Dennis, for taking the time to do up this cool how to article! :banana-dance:
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Re: Making inline motor brackets

Postby Brumos RSR » Mon Feb 27, 2017 11:36 am

Holy smokes this is incredible Dennis
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Re: Making inline motor brackets

Postby walker » Mon Feb 27, 2017 2:36 pm

-
Last edited by walker on Tue Feb 28, 2017 2:26 am, edited 2 times in total.
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Re: Making inline motor brackets

Postby 4424ever » Mon Feb 27, 2017 6:12 pm

Thanks now I'm looking at hole punches
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Re: Making inline motor brackets

Postby dreinecke » Mon Feb 27, 2017 8:19 pm

Ok, so this is so cool! Really excellent work Dennis and thank you for sharing...and it proves there is NO way I'll ever try this!

Why?

Remember this? This is usually how my brass builds go...

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Re: Making inline motor brackets

Postby Broman62 » Mon Feb 27, 2017 8:37 pm

Just fantastic info GCN!!!
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Re: Making inline motor brackets

Postby TuscoTodd » Tue Feb 28, 2017 10:53 am

WOW! GREAT tech article!
:text-thankyouyellow:
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Re: Making inline motor brackets

Postby waaytoomuchintothis » Thu Jun 29, 2017 7:32 pm

Dennis, my punch set arrived today, and I decided to order the mount, too. If you order from Roper-Whitney, they charge $50 plus- minimum for shipping. I bought the exact same R-W mount used (can't wear out cast iron!), on Ebay for a dollar cheaper than R-W, and paid only $10 shipping. R-W only uses 1 or 2 day shipping, so a 5 pound casting costs $52 to my address. Normal shipping was so much less- $10.

Frankly, I can see all of us doing this. I am tired of throwing away brass that just couldn't be done right, messed up in drilling no matter what I did. My Harbor Freight brake&shear broke after less than a year's use, so I moved up to a much nicer unit in a 3-way sheet metal machine. I should be cranking these little buggars out by next week.

You did good, Dennis! Thanks.
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Re: Making inline motor brackets

Postby walker » Sun Jul 02, 2017 12:00 pm

What a funny thing - I make an article about another way to make brackets, put it in, and two hours later it has disappeared.

Something wrong with the forum, or with me ? Would be nice to learn, if so.

Roland

I´ll put it in once more, no problem.
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