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JK 25K Hawk motors reliability? Poor lifespan?


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#1 Big Al

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Posted 13 October 2017 - 07:06 AM

Hey gents,

 

hoping to get any feedback regarding these motors. We run these as a club motor with plafit type chassis and 10/38 tooth gearing in a side\slight angle winder setup. Care are generally between 120 to 150 grams total, using vac formed bodies.

 

Having got back into the club acing stuff locally here after a few years out of it, I'm finding these motors to be very unreliable? What is a good expected lifespan for a motor? a month? 4 race meetings? 

 

I have to field 4 cars in total, 2 for myself and 2 for my kid, so at t a throw, it's 4 motors at a time. I believe I have sufficient skills to set up a quiet car, with a well lubricated drivetrain, nothing binding anywhere, and we can generally get into the top 6 as far as lap times go, but, I'm finding motors go "soft", or almost start to burn after a few race meetings?marshals etc can smell the motor\car and it ends up being mine. Recently installed for a 1 month series, 4 meetings of 12 minute racing per meeting, or, 48 minutes runtime, and the motor was too hot to touch after the last race?

previous 4 race meeting, that motor lasted 3 heats and started slowing down?

 

My kids motor had what looked like string coming out the cooling holes on his motor, which I carefully removed, but I think it was somehow "part" of the motor, or wrapped around the axle next to the stacks? I can see something similar on my other motor?

 

What is the correct setup procedure for these guys please? because my wallet, and my enthusiasm is starting to fade with the poor performance of these guys..

 

PS: other drivers have similar comments, and other drivers have no idea what we're talking about.. Are they THAT inconsistent?

 

I'd appreciate the correct run in process and any other feedback you guys who may also use the motors can provide..

 

regards

Alan Paterson


Regards,

Al Paterson
Cape Town, SA
 





#2 Racer36

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Posted 13 October 2017 - 07:32 AM

A raceway near me uses them in rental cars. They are over a year old with a million (ish) laps on them and none had failed the last time I heard. I truly don't think they go fast enough to blow up.

I have not used the water break in on any of those, but I would think the same process would apply.


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#3 Samiam

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Posted 13 October 2017 - 07:48 AM

Track voltage?

 

What type of power supply?


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#4 Ramcatlarry

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Posted 13 October 2017 - 11:46 AM

Keep the DC voltage close to 12.  NEVER use them on the 18 volt power supplies.


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Larry D. Kelley, MA
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#5 Bazzie

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Posted 14 October 2017 - 02:14 PM

What Sam says or too low gear ratio could cause heat (i.e. Too high a load on the motor)


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#6 Eddie Fleming

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Posted 14 October 2017 - 03:04 PM

I am sorry I have no experience with that motor or chassis, but you indicated that some club members do not have problems. Sounds to me like you need to talk to these people about motor break in, setup and gearing.

 

Good luck.


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#7 MarkH

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Posted 14 October 2017 - 03:42 PM

I have used these for my house - party cars. I geared them to run about half as fast as a H7. So on my track the H7 is a 10-35 ratio. Pretty sure the party cars are geared 9-36. They top out real fast but it is all the partying crowd can really handle.

They probably have around 12-14 hours on them. I did not break them in using water. They are in my old Champion Turbo chassis so they are moving a lot of weight.


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#8 Ramcatlarry

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Posted 15 October 2017 - 12:32 PM

A Hawk-7 is rated at 40K+ rpm and the Hawk-25 is 25K rpm. If they are geared the same, the H-25 is still half of the top speed.    What is the power supply/track voltage?


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#9 Steve Ritter

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Posted 15 October 2017 - 09:20 PM

We Run The Hawk 7 and the hawk retro motor exclusively here. On the hill climb and also an oval. I gear mine 13 pinion 35 spur gear JK chassis vacuum body. I get 6 to 12 races out of a motor and consistently in the top three. We run the voltage about 13.1 volts. Retro racing running at 13.6. They get a little warm but they last. I just started breaking my in underwater for the first time about two months ago. Don't know if there's any change in the results. But without the water I break in for a hour or so. Till you look in the can and the brush have seated.

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#10 Steve Ritter

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Posted 15 October 2017 - 09:28 PM



We Run The Hawk 7 and the hawk retro motor exclusively here. On the hill climb and also an oval. I gear mine 13 pinion 35 spur gear JK chassis vacuum body. I get 6 to 12 races out of a motor and consistently in the top three. We run the voltage about 13.1 volts. Retro racing running at 13.6. They get a little warm but they last. I just started breaking my in underwater for the first time about two months ago. Don't know if there's any change in the results. But without the water I break in for a hour or so. Till you look in the can and the brush have seated.

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break in 3 volts, hour..198fa493e02664b8333449d8b3483df5.jpg175e5ef5619d2e8434feb29d9461e188.jpg

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#11 Big Al

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Posted 16 October 2017 - 01:19 AM

Thanks Gents, appreciate the responses.

 

The track is powered with a 12 Volt 90A/h battery hooked up to a 14.Volt 90 am Alternator. The race control sets the truescale power at 13.7 Volts and it's consistent. Track is one of the oldest built here in SA, but is built correctly, numerous power taps, so it's got very even power all the way round a lap.

 

The class is dictated to a set rule of 10/38 gearing. This is not negotiable. So, everyone has to run the same spec, this motor, that gearing, and sponge tyres. 

 

So, as said, I need to look at the correct procedure to break them in.. This also seems to be a dark cloaked science, local guys just shrug and carry on.. So, as a new user to these motors, what may I ask, is the correct method please?

 

Lastly, does anyone have an idea what is the piece of string doing wrapped around the shaft inside? I have bought two new ones, and they also have this small ball of string inside. is this tying something together, or holding something together, and is it supposed to stay inside the motor?

 

Thanks again chaps.

 

regards

Al


Regards,

Al Paterson
Cape Town, SA
 


#12 Samiam

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Posted 16 October 2017 - 06:46 AM

Al,

 

If this "14.Volt 90 am Alternator." is an automotive battery charger, it is not ideal for slot car motors. Too much AC ripple. Not pure DC.

 

The string you see is the comm. wrap. Keeps wires from getting thrown off and makes it harder for tinkerers to change the timing.


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#13 MSwiss

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Posted 16 October 2017 - 06:56 AM

What diameter tires do you run?

I did the longevity testing on the the original JK Hawk 25.

I got a crazy 233 hours and over 3,400 real miles on it, before one of the brushes wore out and the spring arm holding it, wore through.

That car was geared 8-27, with .790 diameter tires.

It was also much lighter than the 120-150 gram cars you run.

You "threw" the comm wrap (as described by Sam).

It probably isn't necessary on a slow motor like the Hawk 25, but if the motor was balanced, or somewhat balanced, before, it probably altered that, when no longer on the motor.

Mike Swiss
 
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#14 Big Al

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Posted 17 October 2017 - 02:16 AM

Hello Mike,

 

they are Scaleauto Sponge wheels, 15mm wide, approx 26 to 28mm dia. 

I'll be trying a fresh out the bag motor tonight at practice rounds, and see how it goes for the next few weeks. I'm also possibly going to drop a drop or two of superglue onto the string to make sure it doesn't unravel etc.

 

thanks for the feedback so far.

 

regards

Alan


Regards,

Al Paterson
Cape Town, SA
 


#15 Ramcatlarry

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Posted 17 October 2017 - 10:13 AM

A clue! The gearing might be to tight.  Tire size affects gear ratio and car load and therefore overall heat load.   10/38 might be fine for some tire sizes and car weights - BUT...

 

We run the retro cars at 100 - 130 grams with 9/28 and .800 tires with no problems.  Our hardbody group runs the same motors with the over one inch tires and 150 - 190 gram cars with 7/33 gearing.  The rollout ratio is about the same and the motors are not stressed excessively.

 

Not sure how an alternator has DC ripple, but a standard battery charger certainly helps let the smoke out of light duty motors.  America (mostly) stopped using them for slots in the 1990s.

 

Spray glue, dry, or heavy glue?   Keep the glue and voltage down.


Larry D. Kelley, MA
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#16 MSwiss

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Posted 17 October 2017 - 10:46 AM

Hello Mike,

 

They are Scaleauto Sponge wheels, 15mm wide, approx 26 to 28mm dia. 

I'll be trying a fresh out the bag motor tonight at practice rounds, and see how it goes for the next few weeks. I'm also possibly going to drop a drop or two of superglue onto the string to make sure it doesn't unravel, etc.

 

Thanks for the feedback so far.

 

I just checked the 8/27, .790", "cross-country" car, which ran at 12.2v.

 

It weighs approx. 100 grams.

 

If you are running the most demanding combo you mentioned, which would be 28mm tires, with a 150 gram car, you would have a car that was 150% the weight, geared the equivalent of 10/27, and running on 12% more voltage.

 

I can see why it might run hot and not last long.

 

If you are the only one having the problem, then it's obviously your problem.

 

If it's widespread, amongst your racers, then I suggest you switch your spec gear ratio, to 9/38.


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#17 JK Products

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Posted 17 October 2017 - 02:39 PM

Hi Alan,

 

I think the biggest issue is likely over oiling the commutator end of the motor and then when the oil gets onto the comm and brushes, they will burn quite quickly and dramatically affect the lifetime of the motor. "Well oiled" is not what you want on the comm end. "Just barely" is much safer as you can't let any oil get on the comm or the brushes. Many people clean out the comm area with contact cleaner to remove any oil after every session or race and then only gently re-lube before use the next time. 

 

Please use oil sparingly on the comm end of the motor shaft. This advice really applies to all of our sealed motors. Over-oiling is one of the biggest mistakes harming the life and performance of our motors. It will often show up as carbon build up or marks on the comm or between the comm segments. You might also see carbon marks or softened brush debris on the brushes themselves.

 

Regarding the wrapping of the comm, this is the biggest reason we don't recommend water break-in. Even though the tie-wrapping string is coated in epoxy to harden it, it is brushed on and not dipped. During water break-in, the tie can absorb liquid and swell, loosening the tie and allow it to come apart.

 

Tim


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#18 Big Al

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Posted 18 October 2017 - 08:41 AM

Tim  thanks very much for the feedback,

 

Oiling is sparse, just enough that I'm satisfied there's nothing binding anywhere. 

The other info I like is possibly the gearing, and I'd like to try it out if I can get the gearing and let's see what happens. Feedback might not be so quick on this, but hopefully, we'll resolve the issues.

 

Many thanks.

 

regards

Alan


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Al Paterson
Cape Town, SA
 


#19 Steve Ritter

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Posted 20 October 2017 - 04:04 AM

Mike, I like the info on not breaking the motor in water. I was wondering why it was not recommended.

Thanks..



#20 havlicek

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Posted 20 October 2017 - 05:28 AM

 

 

I think the biggest issue is likely over oiling the commutator end of the motor and then when the oil gets onto the comm and brushes, they will burn quite quickly and dramatically affect the lifetime of the motor.

I think that, with the hundreds of motors I've opened-up and done quick autopsies on, over-oiling is probably one of the top reasons for untimely motor deaths, and probably has been for many years...decades.  The amount of black, oily sludge in there surprises me still, and it migrates everywhere in there.  The combination of brush dust and oil (*along with god knows what else!) forms something new and deadly, but even worse, in a sealed motor whose insides will never see the light of day, it never comes out.  

The stuff about gear ratios is important too, but I don't know anything about the cars/tire sizes/weights here, so Mike's and others' info is something look into.  I do know that an otherwise good motor can easily fail early with an improper ratio, so it's important to see what the motor is "telling you" about all that.

Last, there's a very simple-but-important truth regarding motors...the higher the voltage, the shorter the lifespan.  Your motor's bearings and brushes will wear much faster.  Spring life will be shortened by the extra heat, causing more "bounce" and even more heat (*a death spiral).  Armature imbalances that are relatively "small" become more significant with higher RPMs too.  A motor that does fine at (nominal) 12V could easily not do so well with a 16% voltage increase (*which is what I think 14V is to 12V).


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#21 Bigtone

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Posted 20 October 2017 - 06:57 AM

You have to run these motors in before use  or they may not last long. I oil lightly both bearings and run it i on my power supply at 6 volts for 10 minutes, the use switch cleaner to clear out the motor. Then oil again fit to the car, set up the gears and run in under load at 9 volts for 10 minutes. Clean out the motor again and oil again, very little on the brush gear end more on the drive end. I use the clean out and oil after every meeting.

 

Tony

 

Tony


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#22 Brian Cochrane

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Posted 21 October 2017 - 07:28 AM

When you break in a motor on a power supply,do not let it hang by the wires while its breaking in.This causes the oil to run down out of the bushing and onto the comm and brushes....


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#23 Big Al

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Posted 26 October 2017 - 08:35 AM

:good:  Am taking in all this info, and will be changing the way I do things.

 

thanks again chaps.

 

regards

 

Alan


Regards,

Al Paterson
Cape Town, SA
 






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