Need advice on powerng an unpowered B unit.

I have some MT F7A units and noticed that some matching unpowered B units are going to be offered this month. I generally like my locomotive power to be... well... 'motive'. I really would hate to canabalize A units to power B units... but... I think that's the only way to do it.
First... does an MT "A" unit chassis fit the "B" unit?
What to do about the couplers... are the "B" unit trucks geared for a direct truck swap?

 

Hi,

It's pretty easy actually. I just finished modifying my SP A-B-B cattle hauler and I wanted all three units to pull. Scraping or using a Dremel Motor Tool is the way to go. If you are good with a small mill, it can be done that way as well. You will need to measure the wall thickness of the A unit and work slowly to match that on the B Unit. You will only need to clear the area around the motor. Also, be sure you have a good running power unit that doesn't heat up, the thinner section will distort if you run the engine in excess of 9volts. Once you have it done, you can pull a Cinder Block around your layout. I was amazed at the pulling power of my three engine consist. Oh, you will also need to loose the light bulb on the B Unit, no need to light up a hulk!

Another thing you might want to consider is to draw bar the units together. With the couplers you have a pretty wide gulf between them. I took a piece of brass Rectangle stock, drilled a hole with a #54 drill bit on each end of the strip. The exact distance is up to you and depends on the radius of your layout. I got mine prototypically apart and they work on our 195mm track just fine. Remove the truck side frames so you can get at the couplers, remove those parts and then using the same screw that was used to secure the coupler, attach the two ends of the brass to both trucks. Then re-attach and haul away. Sounds like a lot of work, but in an hour you can have what you need done, and the look is so much better, and the performance is improved as well.

Cheers

Joe
MTL

 

Thanks,

I haven't seen a "B" unit up close yet so I don't know if the couplers are body mounted or truck mounted. If the couplers are truck mounted, can the "B" unit trucks be put on the "A" unit chassis? Does the "B" unit truck have the gears to mesh with the worm gear on the chassis?

 

joe,
the couplers on A and b units are factory truck mounted. the SIDEFRAMES (with couplers already mounted) are the same for the powered A unit or dummy B unit. The cummy B unit trucks have no gear sets, so you cannot switch the trucks between the two, nor can you power the dummy B unit trucks as they come installed on the chassis.

to power a B unit you have to use an already powered A unit chassis inside the (trimmed) B unit shell (as outlined above).

now, on a totally separate note: you can put your left-over A unit shell onto the dummy B chassis if you trim up one end (round off the square edges and shorten the post on that same end) to allow the A shell to fit on.

i hope this helps.
dave f.

 

The only thing that I would add to Joe's reply is that if you close couple the units, also wire them together. I used a couple of 30 ga wires to connect the two units electrically. This doubles your electrical pick up on both units.

I bought an extra set of F7 truck sideframes so that I could quickly convert between close coupled and independent units. Actually, I bought the extra sideframes to convert an F7 that had Marklin couplers. After I changed the truck sideframes, I changed the couplers on the other set.

Dan S.

 

Speakin' of Bunits, this month there are 4 new paint schemes on them from MTL!!:teeth: Milwaukee Road is nice!

 

Thanks for the info. D&RGW B units are order. Not too sure if I really want to go to great length and expense to power them. Once I get them I'll have to decide.

Joe D'Amato.. your sig indicates MTL and you're from Medford OR, do you work for (or have worked for) Micro-trains? If so, why didn't MTL offer the B units as powered instead of dummy?

 

Hey Grandpa Joe...funny, my grandkids (I'm way too young and firm to be one) call me Grandpa Joe too..how funny.

Yes, I work at MTL now, I'm the Design Engineer there. As for desiging the B unit to be un-powered...before my time, not sure of the reason for that. I have in the works, a plan to modify the insert to allow this but we are pretty spread out now. I have modified a few on my own and it's a easy fix, just need to protect the paint job on the outside, or be prepared to "weather" the engine when finished. I tell you, it makes a lot of sense, my three units can pull one of my kids around the layout!

Cheers

Joe

 

Thanks Grandpa Joe "D"

I wonder if at this juncture the Z scale 'collective' would like to see Micro-Trains make a factory powered "B" unit for future releases; AND/OR, create a separate powered "B" chassis for converting existing dummy units? I'll make a poll and perhaps we can gauge the interest and you could show management at Micro-Trains.