Blue Box Athearn F7s slowing on curves

[chatanuga]

I have three Athearn blue box F7s (2 powered A units and a dummy B unit) that I've had since the late 1980s or so.  A while back, I replaced the motors of the powered locomotives with new Athearn motors since the old motors were starting to wear out.  While they ran smoothly, I had to turn up my transformers (I run DC) a bit more than I used to for those locomotives.

Last year when going through all of my locomotives and doing tune ups/clean ups, I tried a trick on the F7s that I'd read about in Model Railroader where the brush springs are stretched an trimmed.  That helped a lot in the performance of them in terms of the starting speeds.

While they still run nice and smooth, they do have an issue that is quite annoying.  When they go into my 32-inch and 34-inch curves on my mainline, they slow quite a bit, especially when pulling a train, as soon as they start into the curves and then take off when they come out of the curves, which is annoying to have a smooth-running train slow to a crawl and then accelerate like a slot car and then slow to a crawl again.  It's almost like something is binding up or producing drag somewhere.

Any suggestions on what I should check?

Kevin

[mbinsewi]

If it was mine, I'd probably start with some basics. 

If you run these as a set a-b-a, seperate them, and see if you can tell what loco is causing the problem,  eliminate the b unit first. 

Run them in the oposite direction, do they do this no matter which loco is first, and what direction they are going.

Check the wheel spacing, on the unpowered unit as well, maybe one is just a tad tight, and it causes binding going into a curve.

At the same time, check your track spacing in the curves.

Take the shell off, and watch ever so closely, and listen, as maybe it's a drive shaft or worm gear problem.  If the thrust washer is worn on the worm gear, you could get binding.

Since you do regular maintainence, double check the gear towers for any old grease, and make sure each truck can swing freely.

Mike.

[mobilman44]

Mike's advice is right on...........

The key of course is to find out if its a single loco slowing down (and thus slowing the others) or if the problem is common to all.  If its one of the locos, obviously the loco is at fault.  If its all three, well it could be a common problem with the three, but more likely its the tracks.....

BTW, do you have feeders on these curves ?

[j. c.]

how do the motors get power  ? are they orignal conectors ?

 

 

[xdford]

Hi there,  All of the above but also check that your universals have a little bit of play so that they are not rubbing each other while in the curve. I have the older "key" drive universal shafts and had a little bit of an issue when I remotored mine with can motors. I shortened the female universals ever so slightly so they were not in contact...

Hope this helps,

Cheers from Australia,

Trevor

 

[Lone Wolf and Santa Fe]

mbinsewi

Check the wheel spacing, on the unpowered unit as well, maybe one is just a tad tight, and it causes binding going into a curve.

    I have had this problem with Athearn locomotives. If the wheels are spread too wide they cause friction which isn't there on straight track.

[BRAKIE]

Lone Wolf and Santa Fe

I have had this problem with Athearn locomotives. If the wheels are spread too wide they cause friction which isn't there on straight track.

A NMRA gauge will will help with that problem..Thankfully the old BB wheels was easy to adjust to the correct width.

[chatanuga]

So between the projects I was working on today, I did some test running of the F7s, taking them off the train they were on and running them light around the layout.  While I wasn't able to fully check them over, the test running had some interesting results.

The A units (I'll label them #1 and #2) when I ran them alone, still ran sluggish around the curves.  My layout is a sectional around the walls layout (eastbound is clockwise, westbound is counter-clockwise).  #1 had been facing and leading eastbound with #2 trailing and facing westbound.

I removed the B unit, which had its dummy wheels replaced some time ago with wheels for a powered unit, greatly improving its rolling.  They still ran sluggish.

I tried running the two A units westbound, facing the same direction as before and just running in reverse.  Together and individually, they still ran sluggish around the curves.

I then turned the locomotives so that #1 was now facing westbound and #2 was facing eastbound.  Now, there is no slowing on the curves whatsoever.  I added the B unit back in between them, and they still run smoothly.  I put them back on the train as before, and they were able to run with no slowing on the curves.  I even turned down the transformers as slow as I could run them without stalling, and they maintained speed with no hesitation on the curves.

Kevin

[mbinsewi]

OK, well, a temporary fix anyway.  Is this the opposite direction that you usually run them?  Do you usually run them in just one direction?  Sometimes a change in direction is good.

I would still take off the shells, and do some further investigation, along with checking wheel and track gauge, drivetrain, etc.  They should run the same, no matter which direction.

Sometimes with constant running in just one direction, the locomotives always turning the same way, subtle things can show up.

Good luck!

Mike.

[xdford]

Hello Kevin,  With the body off the frame, can you check that the universals are not rubbing against the vertical pickup that goes around and over the universals on the drive train. 

I have minimum 18" radius curves (most of mine are compound and larger even though it is only a 4 x 8) and I had a similar issue to you, particularly under load.  I provided more clearance for the universals and it was OK. 

I do not run with the extra cast weight provided with the "Super Geared" units as I remotored them with dutch can motors many years ago but if yours is in place, it may be difficult to see if the universals are making such contact.  

Good Luck and hope you find it with all the advice given you,

 

Cheers from Australia

Trevor

 

[mbinsewi]

Something I thought of this morning, the next time you service these out, if you still have the stock sintered wheel sets, think about replacing them with new nickel silver sets.

An F7 or 9 used 40" wheels.

http://www.athearn.com/Products/Default.aspx?ProdID=ATH40028

You can usually find them cheaper on line, or even a LHS if you have one in your area.

They sure helped mine run better.

Always check the wheel gauge before you install them.  It's an easy job, pop of the bottom truck cover, remove the old, drop in the new.

Mike.

[wjstix]

I'd certainly second the advice to open the models and observe the interior workings closely. It sounds to me like something is binding in the drive train somewhere along the line that is causing a problem. Perhaps the new motor isn't perfectly in the middle or something and it's causing binding in the universals when going one way - or the motor isn't seated properly, and it's raising up a little on curves (causing binding) when going one direction. As Yogi said, you can observe a lot by watching.

[Redvdub1]

All of the below plus check the axle gears for slippage.  Pop the bottom cover, pull the wheels, give a little twist...if the wheels rotate under "light" loading..replace

p/n 60024. 

I know it's an Athearn engine and gear slippage is usually associated with Proto diesels..but I've seen it on older Athearn diesels also. 

[mbinsewi]

Redvdub1

.but I've seen it on older Athearn diesels also. 

Oh yes, some of the runs from the 90's.  I've run into on SD45's & SDP40's, so far.

Mike