# Better tracking with your "Floppy drive" - USA 3 - axle blocks



## SD90WLMT (Feb 16, 2010)

It has been longer than I expected to get this going and put up here...But as promised I'm here now!!

While there has been a great deal of discussion over the 3 axle trucks, made by USA Trains and found in these locos - SD40-2, PA-1, SD70-Mac - there have also been various ideas as to addressing the issue to each persons own satisfaction... Hence this has become a hot topic at times... Not here for that!!!

I'm here to share MY own approach - spurred on by others asking for MY thoughts and maybe finding a solution to a perceived problem. Folks have complained of new units picking switch points, as being the single most common problem. Of course this truck has earned a nick name of "floppy'' due to the fact that the first axle so freely moves or turns in such a wide arc. Indeed it does turn far more than is even reasonably needed for any curve these locos can actually operate on in the first place!! Most are rated if you will for 8 foot diameter curves, pretty small for the locos size!

I spent much time trying to first determine what the issues may be - looked at others own solutions, and what I felt needed to be done to get the best results to have a better performing power truck overall.

What I eventually came up with, built and have run very successfully, is what will be discussed and shared here! Why can I say - successfully - the motor block has exhibited none of the complaints that are typical for this truck. IT runs well, behaves well, frankly is even easier to place on rails, without that darn axle falling some where else, than where you want it!! It also has not developed any of the wear tendencies that most have talked about - worn idler gears or cracked main gears on the axles. The locos performance is smoother, pulls more evenly, the load is in 'balance' on all 3 axles now, reducing some of the above problems.

I have 'worked' My loco much harder than most would have room for - or just plain consider doing in the first place - as a means to not break their toys! This combination I have used has shown vast improvements in pulling power also, a result of a more balanced application of power from the motor to the axles - all the axles, actually reducing the load for each axle in turn.

My rework tackles 2 areas of improvement :

Part ONE....Limiting the side play!

This is what a stock truck looks like with the 1st axle in a fully cramped turn ...looks to me like it could go around a 4 foot circle ...does it need to?

 

And this is the slight amount of right and left turning My modded block comes to ... actually enough to easily turn on less than a 4 foot radius - and geez,.. the locos are rated for a 8 foot circle minimum any way!!!

A Right turn...



A Left turn...

 

Well,.. there's the before and after, but now for the work ...

I start by using both a file for just a quick run over the plastic side to knock off any casting flash, or raised edges that could be a problem, and a complete sanding of the glue area with a 180 sanding board, ask your Wife here guys!! Following this a little rinse off with some lacquer thinner to rinse the surface off for gluing.

Sanding board...

 

area to be sanded - thoroughly here...



These are the parts made to be glued to each side, 2 sets needed per truck - 4 sets for each loco..



This view shows the first part glued in place - followed by a doubler to provide enough thickness that the floppy block will not run over the first piece and still turn .. a real bummer!! ha For all My gluing, I use 'SUPER JET' - a medium ca, from ''Carl Goldberg Models''..



One of the keys to gluing on the motor block is using a dot method of applying glue - in drops, not beads, which really is too much glue! Also all surfaces to be glued are sanded and cleaned prior to gluing.



The second part gets added here...



Once the parts are in place and dry, a glue bead is placed on the seam edges to soak under as needed and seal the edges...

 

I make the parts - glue 'em on both sides of a motor block, and for both trucks, not much really - some time, a piece of scrap abs sheet, and results that are far less expensive than replacing the trucks all together as has been done many times..

In Part 2 - I will tackle the spring that changes the game plan !! 

Thanks, 

.... Dirk - DMS Ry.


----------



## NTCGRR (Jan 2, 2008)

this thin brass stock still allows un/down flex in the truck. Its NOT "lockdown rigid " (Elmassian)


----------



## Greg Elmassian (Jan 3, 2008)

I think Dirk's solution is not "full floppy" (stock), or "lockdown rigid" (Cozad). 

Great to see this developing, I have an ABBBA setup of USAT PA's that are ALL getting stereo sound. 

Maybe they can pull too!









Greg


----------



## SD90WLMT (Feb 16, 2010)

Part 2 - getting more work from the 1st axle!!

OK, let's see what happens now!!

The lead axles trip over anything in their way, when they need to act more like a steam roller, stay on track - on task!!

So what will it take to do this?

Using a flat screw driver to lift each of the 3 axles 'off' - or up in the air - a shelf,.. it becomes pretty clear there is not much down force working for the front axle here! why? There is a spring under a part of a metal guide plate attached to the loco deck, and on top of the motor block, but the supplied spring obviously is not strong enough to create much down force. So by working in this area - by changing to a stronger - heavier spring - we should be able to make some more down force to allow the axle to do some work, if there is more pressure on the axle, there should be more friction between the wheels and the rail - & maybe more traction.. Well,. what can be done!!?? And will it work?

I took this small group of parts off the motor block top. Then went window shopping at the hardware store & searched thru the small springs to find some close matches..These came home and I started playing with them...

I picked a spring that 'seemed' about right, some place to start anyway, I mean it's just a spring - I can choose a different one, buy more or try something else here. But I took one and found it taller and stronger than I felt was needed - so I cut it down to size. ! This went in, placing the parts back in their places. Once the truck was back under the loco - with full weight on the truck I was able to get a good idea of the results, and where this first try was for me...

Did it work - did I need to take it apart again and try a different spring.??

Well - the first time worked out well!! What I am still in the process of is determining different springs to match loco weights of different amounts - as locos all do not weigh the same. Is the loco a track power unit, about 10 pounds? Doe's it have ballast added in the tank??? ...is it a R/C - battery unit, 12-14 pounds? My first loco came out over 19 pounds, and the spring I started with works very well on it, but is too heavy for other locos. The set used for this article was built for a loco of about 14 pounds, and as such I used a lighter spring than My own loco has.

By increasing the pressure of this spring, there is more pressure on the loose axle. The results are - at least on My heavy loco - a first axle that is 'heavier to lift up' than the other 2 main axles are. The last axle is a bit lighter than the first is, and the mid one is nearly as heavy as the first is!! So with increased spring rates here, I now have axles, all 3,.. that sit on the rails, and have enough friction to do some real model work!!

Running the loco has resulted in a very smooth runner now. Also the new spring acts similar to a shock, in that movement thru curves has been dampened. The first axle can and does flex enough going thru curves that it can follow a curve and not have increased wear on the wheels or added wear from increased drag on the rail edges itself. This makes it easier to run down track, and even should reduce current loads feeding a loco, tho it might be pretty fine to measure the differences! Many have simply used a rigid method to lock up this first axle, but this really contributes to increased wear of both rail & wheels...without the ability to flex somewhat the first axle is attacking at an angle the rail sides while going thru curves, causing this increased wear...Yet when it can bend a bit - it follows the curve and rolls with it - not fighting!

Here is a recent assortment of springs I came home with to play with for this exercise!! The smallest spring is USA's original design......the tapered short unit!



This is the one I used for a 14 pound loco, pretty average in all aspects. It was cut down, the end gently bent flat for even support at the base - the large end here, which fits the motor block depression. The small flat washer sits on top of the spring, between it and the slotted plate as an added upper support and to reduce sliding side drag...



The set of springs - cut,.. and for one loco only!



and the spring sitting in the recess of the block..



This completes the parts needed and the work to do the changes to improve a motor block!!


Thanks again!!,

.... Dirk - DMS Ry.


----------



## SD90WLMT (Feb 16, 2010)

Recent ?'s by others regarding My work on these trucks has led me to further examine the limits of a modified truck... 
I recently set up a test flex track to demonstrate how this still allows a truck to flex over a crest - as in a grade transition - either at the top or bottom of a grade change in a layout! 

The work as completed here allows a truck to flex not just sideways, but also up/down so as not to leave wheels hanging in the air going over track work that changes. WE all know we do not build on a "Flat" billiards table, track does have vertical and horizontal curves that trains do indeed run over on our track on Our layouts!! This is real world stuff. As shown in Part 1, the trucks can flex side ways enough to go thru curves more easily, with out tracking problems. Here now in Part 2 are the pix showing the abilities to flex in a vertical plane also. 


The sample for a bottom grade transition... 

 

and at the top of a grade transition... how I set this up, far exceeding most grades we have in a layout.. 



The side views of the motor blocks in each position, showing the wedge shaped opening at this amount of vertical curvature.... 

Lower, .. at the base of a transition...



Upper, .. at the crest of a grade...



This means a truck - Loco - can maintain better wheel contact and improved traction & adhesion providing Us with a more reliable loco, and improved train operations! 

Hence - Engineers - More FUN!!! 

Dirk - DMS Ry.


----------



## Greg Elmassian (Jan 3, 2008)

Hey Marty! Sorry! 

How thin is that brass? I thought it was a thick plate! 

Now I see! 

Greg (Elmassian)


----------



## SD90WLMT (Feb 16, 2010)

Just to add some additional info - the spring chosen to use here, ( for 12-15 pound models ), came from an ACE Hardware store, found in the hardware dept. and is a number 86 spring, and as shown has some taper to it. I cut off exactly 1 1/2 turns, from the bottom - large end - for this project, flattening the next 1/2 circle to help it sit better in the round groove on top of the motor block. They cost $ 0.45 each. 

This is not an expensive project, it does not take a great deal of time or require a high degree of skill to do the work and accomplish a BIG improvement in the USA trucks tracking abilities, while eliminating the typical complaints.. All in all - it creates an overall better loco in the end result, while also increasing the locos pulling abilities, and reducing and balancing the loads to all axles, actually reducing the ''stress'' that goes towards some of the trucks typical broken & well known gear and axle problems also. 

Dirk - DMS Ry.


----------



## Doug C (Jan 14, 2008)

Thanks Dirk for taking the time to put this together and post !!


----------



## SD90WLMT (Feb 16, 2010)

I'll ''resurface'' this thread for help as desired... 

Greg I thought you wanted to host this thread on your site?? 

One reason for my choice in going with this solution was I cannot justify the expense of a pair of A/C trucks - ( $150.00 ) when it takes about 5 bucks and less time than converting to A/C and replacing the USA truck .... 

You definitely need some down pressure on the loose front axle, more than stock is much better and goes along ways towards preventing derails...limiting side motion while allowing some movement, also greatly helps in the tracking dept - keeps the axle from getting distracted from it's job..! 

Again, - this modded trucks can go thru a 5 ft radius curve... 10 ft circle.... 

Dirk - DMS Ry.


----------



## SD90WLMT (Feb 16, 2010)

it was on page 5...


----------



## eheading (Jan 5, 2008)

I have found this thread most interesting and educational. Some of you know that I strongly prefer Aristocraft to USAT locomotives on my railroad. However I do have one SD40-2 operating on my railroad. My own experience on my railroad is that I have concluded that the stock 3 axle motorblocks on my SD40-2 perform much more reliably than my engines with 3 axle Aristocraft motorblocks. What I am referring to as "more reliably" is that I rarely have a derailment with the SD40-2 while I have more frequent derailments with the Aristo motorblocks. 

I have not had the SD40-2 long enough to determine if long term reliability (ie. motorblock gear failure) will be as good as my Aristo motorblocks have given me, but time will tell that. 

Just my personal experience. I might also add that I think the above "fix" is clever and ingenious and as stated, is a LOT less costly than replacing the motorblocks. 

Ed


----------



## Cougar Rock Rail (Jan 2, 2008)

Thanks for finding that thread Dirk--greatly appreciated. 

Keith


----------



## SD90WLMT (Feb 16, 2010)

Let us know how your changes work out Keith.. 

Good luck in your efforts, 

And I'd like to ask you - what changes did you make to the chassis that prompted this approach? speaker cut outs perhaps? What got in the way.... 

Dirk


----------



## Dick413 (Jan 7, 2008)

Dirk 
Can you show your mods to the side frames and how you changed the motor mount? 
thanks Dick


----------



## SD90WLMT (Feb 16, 2010)

Dick - can you expand your thoughts here?!! 

For the rework above there is nothing done to the side frames or motor mount.... 

Dirk


----------



## Dick413 (Jan 7, 2008)

Dirk 
I was looking at your pics. on the other thread on sd40-2s and was not sure if you also had changed the side frames and mount. 
thanks Dick


----------



## SD90WLMT (Feb 16, 2010)

could not find the sd40-2 thread...? 

But yes, I have been working up a power truck useful for older locos.. SD-40 series to SD70 standard locos... 

Based on a SD70 motor block, and wheels 
side frames - SD40-2 
but, metal brackets from SD70, for increased turning clearances. the large plastic ones take up a lot of real estate under the floor frame when turning. And I have ventured into more scale built loco chassis frames... 

Requires adding side plates inside 40-2 side frames to mount newer style 70 metal parts, both bolster mount and forward spacer bracket also. 
built a guide tool to ''locate'' the new side plates during glu-ups... 

I also do rework on any side frame that goes on one of My 'dual - motor' power trucks, as they do not have a pivoting axle, but rather become a rigid axle block. This requires those small bearing inserts be installed for the forward axle to support the side frames evenly and as such allows the mid-axle to be sprung separately from the two end axles, creating a working suspension across the three axles. As the mid axle is un-powered it cannot prevent the two end axles from doing their job of making traction to move the loco. 

Lost yet?!!! ha!! 

Dirk - I have gone way out on a limb - for power truck mods here. They work and I like 'em.


----------



## Dick413 (Jan 7, 2008)

Here is sd40 post http://www.mylargescale.com/Community/Forums/tabid/56/aft/127748/Default.aspx about half way down you posted a pic. I also have to ask what coupler did you use after your changes?
thanks for info 
Dick


----------



## SD90WLMT (Feb 16, 2010)

......Dick, ......and for the second answer here, what coupler do I use? 

I do not always take the easy road in projects Dick.!! 

I install the new style 'G' KD coupler in a custom mount bringing it to correct height and extension from the end sheet with the details surrounding the opening included and typical for a diesel loco. 
I am after the correct look here.............. and as I run higher coupler loads than most, I do not want a 'bent' coupler shank to pull with or one mounted on a stock long shaft mount that can flex also, forcing it to drop the coupler under loads... 

I have mostly been using a long shank coupler typical for use on a freight car! the longer shank gives nicer pivots, also matching a real coupler. I add a filler in the slot to eliminate any fore and aft movement, making the swing as long as possible - ( the remaining hole is at the rear of the shank ) 

I believe I also use like 6-32 screws in threads to mount the draft box to the loco mount.. want it very strong ( I have had one loco drug backwards by the mount with no damage, - we're talking dragging about 20 pounds backwards here.... 

While this may sound limiting in curves, I have run on curves in the 10 ft radius club, and not had a problem. I don't run on smaller curves at any host layouts for modern mainlines. 

Got anything in mind Dick?? 

Dirk


----------



## Dick413 (Jan 7, 2008)

Dirk I like you like to run long trains when i can. this is the first sd 40 i have, going to work on the motor blocks first then look at the rest. the frame ends are like fish out of water so before i even think about mounting couplers i have got to stiffen 
that up. Thanks for your help. 
Dick


----------



## SD90WLMT (Feb 16, 2010)

Dick 

How long a train do you like running? multi- lash-ups for locos..? 

Dirk


----------



## SD90WLMT (Feb 16, 2010)

If the site was efficient this would not happen...
difficult to post online.
Can't post from My phone anymore!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

ARRRRRRRRRRRRRRRRRRRRRRRRRRRRR. G H..

This is not FUN anymore!!

just trains are fun, back to work....

Dirk


----------



## Totalwrecker (Feb 26, 2009)

Dumb phones are God's way of telling you to get back to the real fun! TRAINS!!!! 

edit: I believe I've mentioned that I'm not qualified to have a smart phone.....









My day starts making saw dust.... 

John


----------



## TAAudi (Dec 6, 2012)

hi all, if you interested in ..... because I havn´t continued my tread.

this is my modified SD40-2 http://imageshack.com/a/img819/5126/c34c.jpg feel free to see this: http://www.flickr.com/photos/[email protected]/ 

greetings from Germany 
Thomas


----------



## Dick413 (Jan 7, 2008)

Thanks Thomas for your pics. 
Dick


----------

