Initiated the more detailed as testing
First DC test high lights.
On the first engine Engine, # 50:
1. Max number of cars is 6 on 2.5% grade (note it does not pull a nominal train of 8 cars)
2. MSV (minimum sustained velocity) voltage is 4.7 Volts- should be between 2 & 3 volts
3. MSV is 7 SMPH- should be between 2 & 3 SMPH
4. 12 volt V is 50 smph
5. Weight is 171 g (very light)
6. Noise is above norm at high power
7. Nominal train V on level track is 39 SMPH
Second & third engines on DC (engines # 70 & #80):
1. Similar results to the first.
2. Third pulled better. Second is the poorest so far
The fourth, engine #60, was like the first & third on DC
Source seems to be gear drag
Pulling power problem is likely due to weight.
Next steps were to do a deep dive
down on one engine. Chose the second engine because it was distinctly the poorest puller.
- Ran on DC only. Removed the decoder actually just wired the decoder out of the circuit.
Results:
- EO speeds improved
- MSV voltage reduced from 5 to below 3 Volts
- Pulling was not much changed- there was a distinct clicking sound implying a gear issue
Next ran a motor only test. It did not make a lot of noise.
Unfortunately there seems to be something wrong with this motor or it has a bad connection. Motor failed to run during this test.
This unit had lots of thick grease that needed to be replaced
The clicking sound brought clean, adjust & tune (CAT) to the top of the list. This activity identified a couple of problems:
- Both outside axle gears were stripped such that only half the gear teeth were there. This is the source of the click. Also only two axles were 100% active. The other two are only active for about half the time. This will cause several problems.
At this point it was decided to see if this problem was common to the other engines:
- Found that there are at least two variations in these engines. The first engine #50 has a totally different tower gear(larger), truck connection, gear geometry & electrical pickup. This is the version that is shown on the web site schematics and is what Bachmann has parts in stock.
This engine gears were cleaned & lubed. It was then configured in the DC only configuration to see what improvements were made on this engine.
Looking at the third engine #80, it is a similar truck configuration as the engine#70. While taking it down to get at the truck gears to see if they are intact, it was found that at least one tower gear coupling just spun on the metal tower gear shaft. This is a additional problem.
Again this gear set was covered with thick grease. The drive wheels & axle gears were intact. The outside set were swapped with engine #70
The upgraded engine #70 was run with the DC circuit test.
One of these engines will not be fixable without additional parts, which do not have a source for replacement.
Client is sent a fifth & sixth engine with the hope of getting four good ones. Possibly will have 5.
The noise issue is the final challenge. There are several steps involved:
1- install a motor damper between the motor & the frame.
2- Several of the motors were not snugly fixed to the shell. The metal bolt on the plastic motor shroud has to be carefully tightened.
3- where possible the gear noise should not be allowed to enter the shell cavity. The later design is easier than the older version.
4- The larger tower gear of the latest design creates a siren tone. A potential solution is to cover the openings. The bolt head tops are above the tower gears. Placing a cover on these bolt heads can block this noise from entering the shell cavity.
Covering this gear is used to add weight to the engine. The problem is this weight rests on the bolt heads. For later maintenance reasons these should not be permanently affixed to the bolt heads.
these weights can be held in place with tape attached to the chassis sides.
The older designs do not lend them selves to the cover truck attachment trick.
the older design clip attachment turns as the truck turns. So the weight can not be secured with tape to the chassis. However, tape loosely looped over the truck cover showed a noise reduction. This also reduces the weight added by 1/2 ounce.
5- The attachment of the shell to the chassis needs to be as snug as possible. Again the engines have two different types of attachment design. The first is a metal bolt and a plastic threaded tab off the plastic shell.
This design frequently breaks one or both of the threaded plastic tabs.
The second is a metal bolt held with a metal threaded nut
This later is a more reliable technique.
6- The shell & chassis contact points should be damped with a soft material. This will help minimize the vibration transmission to the shell cavity that tends to amplify the noise.
7- These engines are very light, even with the original design weight bar in place. Using the 1/4 ounce weight slugs, two can be attached to the shell covers for one chassis design. Also, four of the slugs can by be added to the shell.
Three will fit inside the forward roof. One will fit in the cab side. This adds 1 to 1.5 ounces. This adds thirty percent to the engine weight. This will help with pulling power and the speed capability of the engines.
8- To insure consistent electrical conductivity the wires will be soldered to the decoders. The plastic clips will be discarded.
The engines ran faster at every point. This did not increase the number of cars, still 6 on a 2.5% grade.
The end result was a successful reduction of the noise on all engines. As indicated earlier, the engines with the larger tower gear were still the noisest. The level of noise varied between the engines.
The weight addition, replacement of broken parts and the tune up improved the speed at all settings. The MSV ( minimum sustained velocity) was reduced to the normal levels approximately 2.5 SMPH.
The MSV voltage was in the normal range, around 3 volts.
As with the noise. There was a lot of variation between the engines. They all improved over the as received condition.
One of the large tower gear engines previously had its motor replaced with a NWSL replacement. This motor resulted in the fastest running engine. This motor did not have a mess to solidly mount it to the chassis. It was attached on tape and chalk. It still would vibrate when running. Emanating the most measured noise. The maximum & average were reduced by 3 dB’s, which is an order of magnitude reduction of the noise energy.
The task was successful & the GE 70 T engines were sent back to the client.
