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Concerning Hawk motors and their brushes


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#1 Brian Cochrane

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Posted 08 February 2018 - 05:57 AM

I was thinking about the brush orientation in the Hawk motors and why they are turned the wrong direction.

 

Since these motors are not just for slot car use and they fit other applications, is it possible the Hawk motors  are meant for running in both directions in other applications and that is why the brushes are like they are.

 

These motors use a brush that is attached to the spring or brush arm and they are not in a hood-type sleeve like an endbell motor. That means the brush is not supported by a housing to prevent it from rocking back and forth when this type of motor reverses direction. The rocking can cause the brush to possibly catch on the comm if the brushes were oriented correctly when the brushes are new and at their full length with a full radius.

 

Keep in mind that the brushes are on arms that are not fully square to the comm surface because they are not in a square sleeve to hold them in place.The  brush arms are weak which can bend easily.

 

Also may be to reduce arcing when reversing direction.


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#2 JohnnySlotcar

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Posted 08 February 2018 - 10:09 AM

Why do they have comm timing on them?


John Austin

#3 airhead

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Posted 08 February 2018 - 10:47 AM

What happens when the brushes wear in to the shape of the comm?


Billy Watson

#4 Samiam

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Posted 08 February 2018 - 10:55 AM

Why do they have comm timing on them?

 

Our race motors are custom spec'd by whomever orders them. 


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#5 Samiam

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Posted 08 February 2018 - 10:59 AM

What happens when the brushes wear in to the shape of the comm?

 

In the case of car mirror motors, this would mean your car is 2000 years old and what happens is moot. :D


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Sam Levitch
 
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#6 Cheater

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Posted 08 February 2018 - 11:02 AM

Did you se the post by Haruki Kan in another thread?
 

When I visited a DC motor manufacturer in Tokyo, I asked this brush orientation issue of FK(130) motors to their designer.
He told me the present orientation is right and on purpose.
Those motors are originally designed for moving door mirrors or display monitors of cars.
The less contact between brush and comm makes the less friction.
If brushes were seated perfectly on comms, motors would have more troubles and much shorter life.
Those motors are designed to run less than 8,000 RPM at 12 volt while slot car motors run 40,000 to 50,000 RPM.


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#7 Cheater

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Posted 08 February 2018 - 11:17 AM

Why do they have comm timing on them?


In a three-pole permenent magnet DC motor, comm timing is not necessary for starting, which would be the case with a two-pole PMDC motor.

As I see it, comm timing is basically a mechanical speed control.

In a PMDC motor, the motor acts as both a motor and a generator at the same time. That is, while power is applied to rotate the motor, the motor is also generating a voltage termed 'back EMF', (EMF meaning electromotive force, i.e. voltage). It is termed 'back EMF' because it opposes the direction of the applied voltage. When the back EMF grows to equal the applied voltage, the motor has reached its maximum RPM.

Increasing the timing of a motor has the effect of making the motor a less efficient generator, which allows the motor to reach a higher RPM before the back EMF equals the applied voltage.

There are other effects that result from comm timing as well, but this is the basic effect.

Here's a very basic web seminar on brushed DC motors that actually mentions slot cars. It will be too basic for many here, but for some it will be a good grounding.

 

Brushed DC Motor Basics


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Gregory Wells

Never forget that first place goes to the racer with the MOST laps, not the racer with the FASTEST lap


#8 Brian Cochrane

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Posted 08 February 2018 - 11:21 AM

All good questions that I knew would be asked.

 

I'm sure the manufacturer of the motors has a standard of each type. You pick the type and then make small changes such as the timing you would like, the spacers you want, the magnets you want, etc. Without literally making an all new motor from scratch, just subtle changes within the guidelines of the basic motor you chose to do it to.

 

The other question asked was what happens when the brushes wear in. By that time there will be less spring tension and the brushes will be more square to the comm and when the motor is run in reverse the brushes will hold to the comm better because of the matched surfaces.



#9 MSwiss

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Posted 08 February 2018 - 11:47 AM

(1) The rocking can cause the brush to possibly catch on the comm.

(2) The brush arms are weak which can bend easily.

 

1 - I don't think so. Not where it would lock up the motor.

2 - I disagree that they can bend easily. Not in racing.

Who has ever heard of a brush arm bending in a bad wreck, and the motor performance being effected?


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#10 slotcarone

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Posted 08 February 2018 - 12:12 PM

I had it happen once in a wreck. Really fast motor lost a lot of speed and was definitely in the motor. Could not see anything amiss in it.

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#11 MSwiss

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Posted 08 February 2018 - 12:17 PM

So the "weak" brush arms weren't a twisted mass of copper? Lol

I just don't see how they could bend, unless the bushings disintegrated.

Falcon 5's use to change speed in bad wrecks, from the comm twisting, either advancing or retarding the timing.

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#12 slotcarone

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Posted 08 February 2018 - 12:26 PM

Brushes looked fine. I am thinking maybe the magnets moved?

Mike Katz

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#13 Brian Cochrane

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Posted 08 February 2018 - 12:43 PM

I'm saying if the motor has many other uses and it had the brushes oriented in the correct direction, the use of it when in reverse when the motor is new and not broken-in may cause it to either not seat in properly and cause damage and that is why they may put the brushes in the way they do. I don't think it will twist up the brush arms; it could cause the brush to tooth out like a buck tooth.

 

I'm just saying this might be the reason for the brushes installed the way they are. The brushes are pushed in to the arm with a slot connection and going forward and reverse with the brushes when new may loosen or cause the brush to not break-in properly. The brush seats in faster with only two sides of it touching the comm, plus there is less friction on the comm because there is less surface coverage.

 

In order to retool and make the brushes for a one direction spinning motor would probably double the cost of the motor.

 

PS: These motors when in a crash and maybe hitting a stopped object while your finger is pressing the trigger will give 13 volts to a motor that is not spinning which will heat up the brush arms and kill their tension. It will also pit the comm and/or heat up the wire on the pole of the arm that is in the power mode. It will also blister the comm if it gets hot enough. Take a crap motor and hold the shaft while putting power to it and see what happens...

 

Even if you stick a pin inside the motor to clean out the comm slots it kills these motors. That's how sensitive the brushes and brush arms are.

 

I am not directing this comment at anyone; it's just a general comment. Thanks



#14 MSwiss

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Posted 08 February 2018 - 01:09 PM

I agree with all the above, but I'll add, if you lock up a traditional motor, it will kill those brush springs, also, and probably worse.

I can probably count on two hands how many times I've seen a traditional spring pop like a fuse when something was preventing the motor from turning.


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#15 Matt Sheldon

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Posted 08 February 2018 - 01:38 PM

Brush orientation was designed by Hyundai to allow ice buildup and debri to pass while allowing brush contact to remain constant. This was done specifically for their car mirrors that are used in extreme climates. The glue on the arms was done to limit the arm from lifting while ice was passing.

They also found that a vented can works better as a can with no hole retained/created too much condensation.

 

I agree with Mike's responses.


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#16 MSwiss

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Posted 08 February 2018 - 01:54 PM

Very interesting, Matt.

Regardless, the brush orientation on these motors, while always a perceived issue, was never a real life issue until the latest batch of hard brushes.

With the pre-7R motors, with RTRs I had in my case, if a customer was planning to use one for my Wednesday night competition, it was easy to find one that was OK.

I could run it on the King, on 12.2V, and within 15-20 laps, it would pick up .2-.4, and I could determine if it was suitable for the customer, to be competitive, or if it was better for the five-year old girl who is just looking for a car with a pink or purple body.

PS: Matt, when you converse with Mill on FB, how do you keep track of what side of an issue he is on at any particular moment?

Do you use a spreadsheet? LOL.


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#17 Matt Sheldon

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Posted 08 February 2018 - 02:03 PM

PS: Matt, when you converse with Mill on FB, how do you keep track of what side of an issue he is on at any particular moment?

Do you use a spreadsheet? LOL.

 

I don't think it is possible.


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#18 Racer36

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Posted 08 February 2018 - 02:33 PM

Hyundai? That's scary. I was a mechanic in a Hyundai dealership for 18 months. Longest five years of my life...


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#19 MSwiss

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Posted 08 February 2018 - 03:06 PM

MSwiss said; PS: Matt, when you converse with Mill on FB, how do you keep track of what side of an issue he is on at any particular moment?

 

Matt Sheldon replied: I don't think it is possible.

 

Mybil.


Mike Swiss
 
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#20 Brian Cochrane

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Posted 08 February 2018 - 04:24 PM

Here's another thought about these motors. Did you ever take one of these motors or any motor for that matter and race it around the track and see what times it runs, and then put it on a break in box and run it backwards for a while? Then put it on the track and try it and it is slow as chit?

 

Well, in my opinion, that's how touchy brushes can be to the speed of a motor. When you run the motor backwards it knocks off the nice edge that the brush had on it from rotating in the correct direction and by running it backwards you just changed the brush enough to make your motor slow. Sometimes it takes the motor a while to get back to it's happy spot and sometimes it never will be happy ever again.



#21 MSwiss

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Posted 08 February 2018 - 05:15 PM

Brian,

 

I'll try that tonight if I get a chance.

 

How long do I have to run the car/motor, backwards?

 

Making it perfectly clear, I'm not just trying to give a hard time. I really admire you. You collect all the cool stuff, I wish I had as a kid.

 

And I really like your "march to my own beat with Retro chassis construction."

 

But so much of your theory and scenarios are based on purposely abusing the equipment.

 

"You ever notice how your car doesn't handle the same, after you drop a cement block on it?" :laugh2:


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#22 Eddie Fleming

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Posted 08 February 2018 - 05:21 PM

I have tried breaking-in a motor and then break-in in the reverse direction to try to even out the seating between the two brushes. Then I did more break-in in the normal direction. I would not recommend trying it. Of the two I tried one runs pretty well and one not so much. 


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#23 Samiam

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Posted 08 February 2018 - 06:35 PM

.Sometimes it takes the motor a while to get back to it's happy spot and sometimes it never will be happy ever again.

 

This is true with people, too. 
 


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#24 Matt Sheldon

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Posted 08 February 2018 - 06:40 PM

Here's another tidbit about the brushes say in the newer Retro Hawks...

 

They are hard and hard bounces more than soft. That's where the two-speed issue comes from in my opinion. When the motor reaches a certain vibration the brushes bounce on the comm. And if you turn the power up a little more it gets past that vibration bounce and kicks into overdrive. If I have a motor with this problem I bring the power up just before the shifting point and let it run in there. It will vibrate until the bushings free up and usually be a fast motor.

 

Before you put it in the car, rinse the bushings out good with lighter fluid to remove all of the particles that may be in the bushings. Reoil with clean oil and go racing.

 

You are getting warmer. The brush bounce however is not from the brush hardness.


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#25 Samiam

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Posted 08 February 2018 - 07:28 PM

PS: Matt, when you converse with Mill on FB, how do you keep track of what side of an issue he is on at any particular moment?

Do you use a spreadsheet? LOL.

 

There's an app for that. :D


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#26 idare2bdul

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Posted 08 February 2018 - 09:19 PM

The most basic problem is how much performance, reliability and consistency of manufacture can you expect from a cheap motor. Racers seem to want cheap (as opposed to relatively inexpensive) motors. Racing puts a lot of strain on any motor but racers seem to prefer these sealed toothbrush/car mirror motors instead of higher quality rebuildable motors.

 

You guys voted with your wallets and the importers have tried real hard to deliver. They do specify many of the things they have found that give us pretty good value but at times you might get a bad batch. When it happens to the motors you are running then it does get a bit irritating.

 

Makes you wonder why there have always been more chassis builders than motor builders.


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#27 Brian Cochrane

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Posted 08 February 2018 - 11:16 PM

I'm doing alright racing with the Retro East group. I don't care what the motors other applications are. When it comes to the cost of the motor,I have no problem with that. I use rear tires that cost more than my motors and I only get one race out of them. I have more money in my tire program than in my motor program.

 

Like I always say, "Slot car racing is the cheapest form of auto racing on the planet." You ever price a motor for a real race car?


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#28 Shiggy

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Posted 09 February 2018 - 01:11 AM

So the "weak" brush arms weren't a twisted mass of copper? LOL.
I just don't see how they could bend, unless the bushings disintegrated.
Falcon 5s used to change speed in bad wrecks, from the comm twisting, either advancing or retarding the timing.

 

I have had a H7 brush arm break off in a crash. Not a result of worn-out brushes. The remaining one was at ~50%.


D. "shiggy" Person

#29 tonyp

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Posted 09 February 2018 - 07:48 AM

Mabuchi has been putting brushes in the FK 90 degree off style for as long as I have been in R/C. In the '80s and today their 550 motors come this way. Igrashi, on the other hand, had the correct alignment on their R/C motors.


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#30 MSwiss

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Posted 11 February 2018 - 12:38 PM

Here's another thought about these motors. Did you ever take one of these motors or any motor for that matter and race it around the track and see what times it runs, and then put it on a break in box and run it backwards for a while? Then put it on the track and try it and it is slow as chit?

 

Well, in my opinion, that's how touchy brushes can be to the speed of a motor. When you run the motor backwards it knocks off the nice edge that the brush had on it from rotating in the correct direction and by running it backwards you just changed the brush enough to make your motor slow. Sometimes it takes the motor a while to get back to it's happy spot and sometimes it never will be happy ever again.

I just tried it.

 

I took about 10 laps to make sure I got a good lap in.

 

The last one was 4.621.

 

I ran the car backwards on the tester at 6V, for about 5 minutes.

 

I went back on the track and first lap, even with tires a bit cold, 4.66.

 

2nd or 3rd lap was 4.63.

 

The 5th lap was 4.587.

 

No negative impact at all, and possibly positive.


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Mike Swiss
 
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Make checks out to Chicagoland Woodworking, Inc.


#31 Brian Cochrane

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Posted 11 February 2018 - 01:14 PM

Very interesting,I have never had that outcome.I never tried doing it with the hawk motor that has the harder brushes.Maybe we are on to something. I'll have to try this again with a hard brush motor.I won't be able to get to this experiment for a while, I have too much other work to do on my slotcar program right now...Thanks for the feedback on this...



#32 MSwiss

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Posted 11 February 2018 - 01:30 PM

I tried it with a pre-7R brush motor.

 

I tried it a 2nd time, running it for 15 minutes in reverse.

 

Again, the motor was fine afterwards.

 

Possibly you are suffering from TMDB* and are confused.

 

 

*Too Much Doug Bauer-lol


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Mike Swiss
 
IRRA® Components Committee Chairman
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#33 Jeff Bonanno

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Posted 11 February 2018 - 09:15 PM

My dad tried this and when he ran the motor backwards, it said "paul is dead, paul is dead, paul is dead"
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#34 havlicek

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Posted 12 February 2018 - 08:53 AM

OK, after countless posts and threads on the subject, it seems like a simple conclusion should be posted about all this:

***All of these type motors have had their brushes oriented this way, and it has never been a problem.  It's possible (*but I don't think likely) that orienting these brushes in the traditional way (*with the brush face arcs corresponding to the arc of the commutator) may cause problems that don't normally exist now, most likely because of more overlap.  Whatever it is that people see as a current issue may have something to do with harder or inconsistent brushes, and that "kind" of issue DOES come up with normal "replaceable" brushes used in other types of motors...C, D, and minican types.  It may well occur in the future in other brands of the same type as the 7R.

So, I think that's about it.  It would be funny if 7R motors still win some races though!


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John Havlicek

#35 Fast Freddie

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Posted 12 February 2018 - 11:53 AM

Turning the brushes in these motors around so that they conform to the comm. will change the timing and overlap, as John said (like going from a vertical to horizontal brush).  Fully seating the brushes in their current configuration will do neither.  However, fully seating the brushes does not get rid of the 2 speed problem.  As in most slot car motors the positive brush will seat first because under normal conditions it wears faster.  Since the brushes don't seat equally then spring tension will not be equal.  After going through all this I decided to do something new and different.  I have a H7 that has one balance mark, fully seated brushes and still has a 2 speed problem.  What I did was something shunned by most racers when it comes to these motors.  I oiled the hell out of the EB bushing and the can bushing.  Current philosophy is to very lightly oil the EB bushing.  Well "Surprise, Surprise, Surprise" the 2 speed is gone and the motor is smooth all the way to 13 volts.  See if it works for you.  I used the lightest Mobile 1 synthetic motor oil I have and it worked for me.  


Fred Younkin

#36 Steve Ritter

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Posted 19 February 2018 - 08:08 AM

The most basic problem is how much performance, reliability and consistency of manufacture can you expect from a cheap motor. Racers seem to want cheap (as opposed to relatively inexpensive) motors. Racing puts a lot of strain on any motor but racers seem to prefer these sealed toothbrush/car mirror motors instead of higher quality rebuildable motors.
 
You guys voted with your wallets and the importers have tried real hard to deliver. They do specify many of the things they have found that give us pretty good value but at times you might get a bad batch. When it happens to the motors you are running then it does get a bit irritating.
 
Makes you wonder why there have always been more chassis builders than motor builders.

 
I have had a H7 brush arm break off in a crash. Not a result of worn-out brushes. The remaining one was at ~50%.

I just tried it.
 
I took about 10 laps to make sure I got a good lap in.
 
The last one was 4.621.
 
I ran the car backwards on the tester at 6V, for about 5 minutes.
 
I went back on the track and first lap, even with tires a bit cold, 4.66.
 
2nd or 3rd lap was 4.63.
 
The 5th lap was 4.587.
 
No negative impact at all, and possibly positive.

I have been reading a lot of these motor posts. Fascinating thoughts and the brushes and the timing and oiling of the End Bell.
I have decided to try something different on my motor. Instead of soldering the lead wire directly to the tabs. I solder it to a female Spade connector. My thought is, the less heat going through that to the brush Springs the better. The downside is reason I probably never tried before as you don't want to come loose in the middle of a race. Just make sure you have it nice and tight and they won't come off, I hope. Just tried it this last weekend on my practice car. No problems.2b8627d87637124e85b37c3c1ffcc246.jpg20180219_060659.jpg 20180219_060648.jpg

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#37 Samiam

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Posted 19 February 2018 - 08:45 AM

To prevent the wires pulling off in a crash or just from racing, put a second wire holder up by the motor. 


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Sam Levitch
 
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#38 glueside

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Posted 19 February 2018 - 09:05 AM

You might be able to safety "pin" them in place also.  There should be a hole in the spade, just take a thin piece of wire and wire tie it in place.


Jeff Strause

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#39 Samiam

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Posted 19 February 2018 - 10:57 AM

Pinning will only stop the wire falling off. Since the wire is pretty much connected directly to the brush arm and it is only held in place by a small blob of plastic, you also want to stop it from moving around. 


Sam Levitch
 
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