USAT motor block - pin connections?

Zerogee

Zerogee

Clencher's Bogleman
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I have a USAT motor block on a recently purchased scratchbuild; I've not used a USAT block before, and I'm a bit puzzled about something..... there are four pins on one end of the block, which I've identified (thanks to an older thread here on GSC) as being outer pair (call them 1 and 4) = motor, inner pair (2 and 3) = track. So far so good.

BUT, is the unit also internally connected, or does it have other terminals/pins elsewhere that I haven't discovered because I've not yet completely dismantled the vehicle?

The reason I'm a little puzzled is that an LGB 4-pin block will not run (on analogue) unless you put jumper wires on each pair of pins (or, as I do for testing purposes, bridge each pair with a small croc-clip!). But the USAT block is happily running away on analogue test power WITHOUT the pins being bridged!

Surely this shouldn't be happening, unless these pins are only for auxiliary use and the track and motor connections are bridged internally? In which case, how do I un-bridge them for DCC chipping?

The other odd thing is that the LED lighting in the vehicle appears to be run from two wires connected to two of the pins - a motor pin on one side and a track pin on the other (ie: pins 1 and 3, which seems to make no sense....). Pins 2 and 4 have nothing connected to them at all, yet the block runs!

Anyone who knows their way around using USAT blocks able to shed any light on this at all?

Thanks in advance!
Jon.
 
Thanks for that, Greg - the info on your site certainly helps me know what to look for, I will open the block up and let you know what I find....

Jon.
 
Well, I've removed the motor block from the vehicle and opened it up - and I now know what is going on! Yes, the original builder has modified the block by bridging across the pins internally, pin 1-2 and 3-4, using a tiny self-tapper and a steel washer across the two brass wires! A simple mod for analogue running because it makes the block entirely self-contained with no need for external wiring connections or jumper leads, and thankfully simple to reverse by taking out the screws and washers! This also explains the rather odd connections for the lighting power takeoff, where he used pins 1 and 3 - because basically pins 1 and 2 are one polarity, pins 3 and 4 the other.

Other than the added screws and washers, the rest of the block looks eaxctly like the pics on your site, Greg, including the "whisker" pickup wires bearing on each axle - I've checked, and the block is picking up well off all four wheels and both skates. Now, again as explained on Greg's site, there are also pickups on the outer frames of the bogie unit (collecting power via the axle ends) but these are not currently - there's that pun again - being used..... would it be a good idea to wire these up too as an addition to the whisker wire pickups, or are they not really necessary?

Jon.
 
A little additional question.... the USAT motor block in this little vehicle seems to run well enough, but it's obviously seen quite a lot of use - the wheels are very well-used, with the plating wearing thin on a couple of them. The gears look OK, and I'm torn between just leaving it alone and thinking about replacing the wheelsets while it's all in pieces.
How difficult (in terms of availability in the UK) and expensive is it to replace USAT wheelsets? Does anyone this side of the pond hold them in stock?

Jon.
 
Zerogee said:
A little additional question.... the USAT motor block in this little vehicle seems to run well enough, but it's obviously seen quite a lot of use - the wheels are very well-used, with the plating wearing thin on a couple of them. The gears look OK, and I'm torn between just leaving it alone and thinking about replacing the wheelsets while it's all in pieces.
How difficult (in terms of availability in the UK) and expensive is it to replace USAT wheelsets? Does anyone this side of the pond hold them in stock?

Jon.
Click to expand...
Try this site,

http://www.g-bits.co.uk/USATrainsMotorBlocks.html

I've not used them but I bookmarked them some time ago just in case.
 
Added to the LINKS section
 
I might just have some spares Jon. Depends on the size of wheel. What is the wheelbase? My ones are for F3, GP9, GP30 etc
Contact me when I get back if you are still hunting
 
Thanks Mike - when are you back?
It's one of the "medium" blocks, 84mm wheelbase. Small wheels (at least compared with LGB...), about 28mm diameter EXCLUDING flanges.
I won't buy any till I've spoken to you again......

Jon.
 
I would not worry about the plating being gone, it's not super robust to begin with.

Did you check for "cracked axles"? That is a vital thing to take care of when the blocks are open. And of course, be SURE to properly align the brass bushings on the axles when reassembling, do it wrong and you chew up the gears pronto!

Greg
 
Be back on Saturday but might be going straight down to Warminster to an open day held by John Steer but will be back Sunday evening.
If the block is medium sized then it should be the size that I may have stocks of wheels sets.........
 
stockers said:
if your using track pick up - I would worry.
Click to expand...


I have about 20 USAT locos all DCC, and the wheels are brass under the plating, and with the multiple wheel pickup I have not experienced problems on worn wheels as compared to my Aristo locos, which are plated steel and leaving one out overnight under a patio roof creates enough rust that the wheels need cleaning the next day.

With the skates, the pickup from the wheels themselves is not as important.

I do speak from experience.

Greg
 
True - your using skates. A couple of the LGB models (Mallet and Rugens) dont have skates and my malley was down to the brass. Ran OK when cleaned but a bit of evening damp and it would stutter like a little 4 wheeler on dirty track. It got some new wheels now.
 
Not saying bare brass is better than the nickel plating, but the skates on the USAT help a lot. I'd run the locos until you get issues that clear up when the wheels are cleaned and running gets unacceptable when they are oxidized.

I have not found that bare brass gets more gunk (dirt, organic matter) than plated wheels.

Regards, Greg
 
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