Bachmann A1 split drive gear

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GWR_fan
Posts: 4822
Joined: Sun Apr 29, 2012 11:57 pm
Location: Antipodes

Bachmann A1 split drive gear

Postby GWR_fan » Fri Aug 03, 2018 4:37 am

I pulled a beautiful old Bachmann A1 "North British" out of storage to test for sale but alas it has a split final drive gear. The loco is part number 32-553. I know the early A1 were criticised for a poorly performing undersized motor, however, at some stage a Mashima motor had been fitted to the model. A very attractive BR blue early crest locomotive but alas is running very poorly.

I did disassemble and clean and bond the gear to the drive axle, however, it has the clunk/clunk sound indicative of a split gear so the gear was not merely loose on the shaft as I had hoped. It now runs reasonably however, not very quietly. A pity as it is a nice loco. I assume that it was made back in the early 2000's, a timeframe when Bachmann excelled at making gears that would split.

Edit: I believe that the loco was also criticised for poor traction with the small motor. My model is good for about four coaches on level track before wheel slip commences.

A Google search and it seems the early black drive gear was suspect and did crack. Refer link -

http://www.rmweb.co.uk/community/index. ... revisited/

Alas, mine is the later supposedly improved white "nylon" gear. Maybe a TTS decoder may quieten the ruckus?????? I have an unused Railroad Flying Scotsman that may become a donor.

Bigmet
Posts: 6211
Joined: Tue Aug 14, 2007 2:19 pm

Re: Bachmann A1 split drive gear

Postby Bigmet » Fri Aug 03, 2018 10:28 am

It's a current model, and Bachmann are efficient at spares supply when they are in stock. It would be a complete driven wheelset as the spare.

The motor. After the initial batch with faulty motors (a defective lot of wire, inconsistent control of thickness, was assigned as the cause) Bachmann switched to a Mashima 1430 until they had a batch of suitable motors of their own design for continuing production. I have had examples of all three motors in A1s, the early one presumably got no wire defects in the motor windings so performs satisfactorily to this day.

The traction. Despite being reasonably heavy, traction was poor, and there was much to do to correct this.
Springs on all the carrying wheels far too strong, lifting weight off the driven wheels, reduce springs.
Spring on leading driver far too soft, increase spring pressure.
Back end of loco resting on tender lifting weight off the driven wheels. Both the drawbar and the fall plate produce this effect, both have to be rectified.

With this done it pulls decently, a dozen coaches on level track. My layout needs rather more than this, for a reliable start on a 14 coach train up a 1 in 80. The capacious interior wil swallow a lot of lead and my Pepp A1s are 600g balanced in the middle of the coupled wheelbase, and pull like heroes.

(The very similar A2 shares a lot of design commonality in the model, as in reality. Happily Bachmann got this one right and it pulls well out of the box. Not that it isn't helped by some additional lead for full-on East Coast mightiness.)

GWR_fan
Posts: 4822
Joined: Sun Apr 29, 2012 11:57 pm
Location: Antipodes

Re: Bachmann A1 split drive gear

Postby GWR_fan » Fri Aug 03, 2018 11:04 am

Bigmet,
many thanks.

GWR_fan
Posts: 4822
Joined: Sun Apr 29, 2012 11:57 pm
Location: Antipodes

Re: Bachmann A1 split drive gear

Postby GWR_fan » Sat Aug 04, 2018 12:13 am

Bending the fall plate ever so slightly to take the weight of the loco off the tender deck has increased traction remarkably.


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