7 replies to this topic

[Pablo]

As vintage builders, we routinely solder the brush holders to the hoods.

Why? Well, "back in the day" of motor wars, glue, heavy chassis, etc. the motors ran hot.

So they invented comm coolers, heat sinks, soldered the hoods, etc. 

 

When the motor got hot enough to melt the endbell, the brush holders would migrate, creating extra friction due to the misalignment, etc. ad nauseum until eventual failure. By having the pent roof hoods connected to the brush holders, the EB was free to melt but the brushes would stay in place. Sounds kind of dumb, doesn't it?

 

Am I wrong? What is your opinion on why we still today solder holders to hoods on vintage motors.

I'm curious because in today's (vintage) world with much improved techniques like Bugenis comms, Havlicek arms, better magnets, etc. we are not having overheating issues anymore. At least, I'm not - been building cars for many years and not one has melted down.

 

What is your opinion?

 

Pablo

[boxerdog]

Maybe for better conductivity between the wire and the brush because the wire was often soldered to the brush holder??

[Bill from NH]

David has got it right. When two parts are soldered, it keeps corrosion out of the joint. 

[Steve Okeefe]

Pablo,

 

I suspect it is still widely done primarily because it is just "period-korrekt" to do so.

 

Also, if you are building your motor with a vintage (lower melting temp) endbell, it is probably prudent to protect everything by soldering the brush hoods (no matter whose armature you're installing).  If you are using a more modern (higher melting temp) endbell this may, as you have pointed out, not be necessary.

 

Soldering the brush hoods was a "bullet-proofing" technique used because there was a genuine need for it, but it was always a pain in the butt to do.  It did help conduct electrical power much better than not soldering, but that's also what brush shunts are for.

 

Bottom line, I don't think there's a "right way" and a "wrong way".  If it's necessary, you do it.  If it's not necessary, seems to me it's builder's choice.

[havlicek]

Besides just doing it to more closely emulate what was done "back then", I also (*as both Dave and Steve mentioned) have always thought it *might* be a good thing for making a "better" or even just a "secondary" current path between the lead wires and brushes *on top of helping in the case of the brush tubes melting the end bell plastic.  As Steve also mentioned, shunts can also *maybe* help somewhat if the brush springs are insulated, but I am pretty sure that the springs were not insulated back then.  The Mabuchi "heat sinks"/brush tubes were still sitting on the plastic no matter what, so if and when they heated up, they were going south fast.  If the hoods were soldered, you got a little more time...until the whole hood/brush tube went south.  Ironically, it wasn't until the later FT160 (Hong Kong-produced) end bells that the "real problem" was addressed by using a better end bell plastic.  I say "ironically" because it's not clear those motors were even used for slot cars.  Russkit had their pot metal end bell later also, but the motor was doo-doo.

I've said it before but the FT16D/26D/36D motors and their "improved" end bell hardware, was a pretty dumb step-up from the earlier versions where the brushes rode directly on the plastic.  The REAL answer was right in front of Mabuchi all along with their lowly FJ13UO end bell hardware arrangement.  Long before Mura-pattern hoods and bottom plates, Mabuchi had what was essentially the same setup on the little "home set" motor.  BTW, there were some weird Johnson 16D motors that used a similar arrangement as well.

You're right Pablo...a lot of the time it's probably not necessary to solder the hoods, but it can't hurt.  Like Steve said, it can be a frustrating PITA though.  When you think about it, there are other things *still* routinely done that may not be necessary.  Some motors get shunts today that may not need them at all.  Motors may use bigger lead wire than they actually need also.  The old Mabuchi wire can carry a surprising amount of current, and is fine for even period rewinds.   I'm sure there are other examples too.

[Pablo]

Thanks for all the responses    I was considering not soldering the hoods on a Cox EB, but I just plugged in my little Hakko N454 25W and am going to do the deed once again...... 

[Bill from NH]

16D brushes or are you using 36D brush heat sinks?

[Pablo]

Stock hardware on Cox 16D EB.