Former Boston FD , B85F-1211 project, Mack Brothers....

[mowerman]

lol 10 minutes,,,,,i have to travel around 2700 miles to get out there,,helmets are way cool...bob 

[mrsmackpaul]

Helmets are certainly the icing on the cake for coolness 

Love it, great stuff

 

Paul

[1958 F.W.D.]

On 7/21/2025 at 3:39 PM, mowerman said:

lol 10 minutes,,,,,i have to travel around 2700 miles to get out there,,helmets are way cool...bob 

He's probably the only BMT Guy that lives closer to Macungie than me......lol

[T-Mack1]

On 7/23/2025 at 1:00 PM, 1958 F.W.D. said:

He's probably the only BMT Guy that lives closer to Macungie than me......lol

I can walk to Macungie.  Although I never measured it, I would say it's about  2.5 to 3 miles.   I do know the Mack factory is 3.8 miles from my house.   Yep, use to take 6-8 minutes to get to work.  

[mowerman]

That’s excellent. I did have three jobs as a teenage kid that were within a mile of my house. I had one trucking job in LA. That was very close as you said just a few minutes. Sure, makes it nice.

[mowerman]

Wound up moving 60 miles away though that’s the way it works in LA. Everything is so expensive down there. You have to move far away from town to afford anything. It’s pretty much the same way everywhere now though.

[T-Mack1]

Latest updates.    We now have spring brakes.    Bought a QRV (Quick release Valve) with balance line, and since the original "service only" rears chambers were "30", got 30/30 spring brakes.  And, a used park brake valve that tests ok, popping out  at 45 psig.   Yes,  I broke down and used plastic DOT air lines.   And new rubber hoses all the way around.

[T-Mack1]

Next,  got some new hood emblems.    old  & new pict's.   Still need B85 and Thermodyne.  the passenger Dog is a reproduction we got at Macungie 

[T-Mack1]

Finally for this update,  Installed the solid-state 3-Phase rectifier to replace the selenium one.   Mounted it to a piece of aluminum and for added measure, added an addition small heat sink to the back.  It's mounted on the inner fender.  The B-model fender insert hides it well.  Plan is to fake out that we still have the old one hooked up, for looks.  Note: we and going to be rewiring the truck real soon, so forgive us using the old wires for now.

[mowerman]

Wow, nice work, bud. Thanks for the update. And yes, plastic lines are the way to go.

[mrsmackpaul]

Good job and great result

 

Paul

[Mark T]

8 hours ago, T-Mack1 said:

Finally for this update,  Installed the solid-state 3-Phase rectifier to replace the selenium one.   Mounted it to a piece of aluminum and for added measure, added an addition small heat sink to the back.  It's mounted on the inner fender.  The B-model fender insert hides it well.  Plan is to fake out that we still have the old one hooked up, for looks.  Note: we and going to be rewiring the truck real soon, so forgive us using the old wires for now.

At the risk of sounding dumb, what is the rectifier for ?

[T-Mack1]

10 hours ago, Mark T said:

At the risk of sounding dumb, what is the rectifier for ?

Not a dumb question.  We don't have a generator.  We have an Alternator.  They make AC voltage so it needs to be converted to DC and that is done with a rectifier.   Although many generators make AC, automotive ones generally make a pulsating DC so no need to convert.  The pulses of DC go into the battery and that smooths it out so you have steady voltage. 

And, the question many people ask, what's the difference between them?  Generators have magnets in them.  Some of them, big magnets that do all the work,  some small magnets that excite a voltage on the parts of the gen to make a voltage that then gets spun to amplify and get the desired voltage.    An alternator doesn't have magnets.  It uses two wire coils, one spinning , one fixed.  By putting voltage on one coil, you can get the desired voltage on the other.  By varying the input voltage you can control the output power to get the desired amount.

Which is better????   Both have good points.  In the automotive world, a generator will create voltage even if the battery is dead as a door nail, where a alternator needs a voltage to start making voltage.   A vehicle with a generator can be push started with no voltage on the battery and will run.  An alternator vehicle  needs a tiny bit a voltage so it won't work on a totally dead battery .   A generator charges at a fixed rate, where an alternator has a variable charge rate, so will charges the battery faster.  At idle, a generator usually drops in voltage (lights dim) where on a alternator, you can vary the input and get more output at idle/low RPM's.

NOTE: : Since energy doesn't just come from nowhere, the energy to get to the desired voltage output is from what ever is spinning the generator (Gas, diesel, Hydro etc etc.).   That's why, once you get a vehicle with an alternator running by jump starting it,  it can make voltage.   

[Mark T]

Ahhh .  I've noticed fire trucks often have components a little different than other trucks.  Didn't know about this one either until you explained.  TY 

[Geoff Weeks]

Automotive alternators and generators both produce power to recharge the vehicles battery.

Both have electromagnets, neither have permanent magnets. (Some small engines use permanent magnets as do some motorcycles, but the amount they can produce is limited)

Modern car and truck alternators all have rectifiers, but they are not separate, they are located inside the case of the alternator, where they can be cooled by the fan.

Generators are somewhat limited in their power output. The field is the stationary coil and the power comes from the rotating (armature). The biggest generator generally fitted was a 50 amp unit, and to make those 50 amps, it had to be turning fairly fast.

Leece Neville was the 1st to produce automotive alternators, but at the time the only rectifiers were big metal oxide types that had very limiting characteristics. Still, they can produce more power at lower RPM.  They had to have remote mounted rectifiers because they were so large and needed a lot of cooling surface area. In most applications the early alternators weren't worth the trouble. In police, fire and tow trucks that might be working at a scene for hours at  a time, lights etc on, they were worth it. So they were retro-fitted or installed when the vehicle was ordered.

Once silicon diodes were invented around 1960 (late 50's) then the switch to alternators with internal rectifiers became ubiquitous. 

Before most fire trucks had 120 volt inverters or generators, you could also tap into the AC output with a transformer and run 120volt lights and universal motors for saws and such.

 Even after the silicon diode, many mfg of large vehicle alternators kept external AC taps for use with a transformer (Delco DN40 and DN 30) as well as various other.

In the late 50's Leece Neville sold a "conversion kit" to convert their early external metal oxide rectifier alternator to internal diodes. I did a write up about installing one on my early Leece Neville.  

[mrsmackpaul]

So to add some useless information here 

The main reasons (in Australia at least) for the change from generators to alternators in the automotive world world is pretty simply

Alternators last much longer than generators in the automotive world as the spin so quick and the generator has a commutator

 

And a alternator has slip rings 

 

The commutator by it's design us very aggressive on the brush gear and it wears very quickly 

Slip rings are nice and smooth and will often last the life of the motor

Alternators as mentioned generate power at a lower speed and the generator commutators tended to come apart in young bucks hotted up cars when giving them a boot full of revs 

 

Paul