I’ve used Bondo for other applications for a long time. I think the amount of heat generated is directly related to the amount of hardener used. Use a lot of hardener and it gets pretty warm and gels very fast. Use a little and the working time is extended and it does not get very warm at all.
Bondo in thin coats is fine (as said in the article).
But if you are adding weight, you normally have a space like an inch deep, and that will have problems with heat.
That’s the warning.
I understand what you say about cutting back on the hardener, probably will make it work, like maybe 1/4 the normal amount?
Of course then you ask what happens if you don’t use enough, does it eventually harden?
greg
I used Bondo to make a new nose for a locomotive, to the wrong profile (oops). It got warm, it didn’t get warm enough to melt nor warp the Aristo body I was applying it to, nor the ABS strips I used to provide support and structure to the Bondo before it fully cured. Some of the fill areas were quite large, maybe 1/2 to 3/4 of an inch deep. Maybe I got lucky, maybe it doesn’t get warm enough to affect ABS of 1/8th thick or so. I dunno.
Since we are on the question of adding weight to locomotives, I am wondering. How do I know how much weight I can safely add to a locomotive? Some of mine could use with a bit more weight so they can generate more tractive effort, but how much weight is too much?
David, I don’t know that there’s a magic formula. The first thing I look at is the locomotive itself and what kind of train the prototype would be capable of pulling. It’s a bit unrealistic to have an 0-4-0 pulling 20 cars up a 4% grade. Maybe 4 or 5 if it’s a heafty 0-4-0 like a docksider. Many of model locos can already outpull their prototypes straight from the factory. We do, however, often expect just a bit more due to sharp curves and steep grades, and there are most definitely some lightweights out there.
If a locomotive is not measuring up, I usually recommend filling a Ziploc bag with a bit of lead shot and draping it over the locomotive. Watch and listen to the locomotive as you add the weight. Keep adding more lead shot until you reach an acceptable level of performance or exceed the extra volume into which you can feasibly stuff the weight. Compare how the motor sounds to how it sounds when you bog the wheels down with your hand. Extra weight can be good, but you have to balance that against the robustness of the drivetrain. You don’t want to tax things too much. If it always sounds like it’s under a heavy load, you’ve probably added too much weight. If you’ve got an ammeter handy, keep an eye on that as you run your locomotive around the railroad. Each loco is different, but watch the amps with no load compared to with a train, compared to with a train with added weight. If you notice it really spiking under certain circumstances, probably back off a bit.
Note also that you’ll want to test your locomotive with its added weight going up and down grade with a typical train in tow. Too much weight could not only really slow the train going up hill, but really speed it up going down, or could possibly cause the motor to surge with its weight and that of the train behind it pushing it downhill.
I wish there was a more definitive answer, but–like so many things in this hobby–it’s trial by experimentation. Try it. If it works, go with it.
Later,
K
David, if I remember correctly, the “rules” of friction applicable to locomotive driving wheels, pulling power is proportional to the weight on them, more or less. So a 20% increase in pulling power would require a 20% weight increase. So if you have an engine that will pull 5 cars but you want it to pull 6, engine weight must go up 20%. Of course, the weight and rolling resistance of various cars and the distribution of weight on engine wheels (driving and unpowered), as well as the “more or less” nature of friction rules, affects the result, but still this might be a useful guideline. And if motor power is the limiting factor, adding weight won’t help.
Bill
Actually, the question was how much weight can I safely add, not how much do I need or how does it affect performance.
So since the questions not asked have been answered 
I’ll answer the ones asked.
First, and foremost you need to look at the drivetrain.
First place is the axle bearings. If they are ball bearing then they can handle pretty high loads. Sleeve bearings will need to be more closely watched for lubrication, and you need to evaluate the fit and finish. At the “end of the line” are axles riding in slots cut into a metal frame, or plastic “bearings”.
To map this to some common brands: Aristo motor blocks, especially the new “prime mover” type have very robust ball bearings, they can take quite a load. USAT uses brass sleeve bearings, good quality but you need to keep them well lubed or they will wear quickly, you also need to note the small bearings in the “journals” will will wear a lot more rapidly. At the end of the line are the cheap little locos with a chassis of stamped metal with the slots for the axles… not likely to handle much more weight.
Now, the axle bearings are just one facet.
Now consider the geartrain, strength of the gears, lubrication. Look at the size of the gears themselves, if there are intermediate reduction gears (and axles).
Again, Aristo makes really nice big gears BUT lubrication becomes critical, and I would advise reading my in depth discussion on my site. USAT locos have an issue with the gear housing cracking where the axles insert, but once that is fixed, they are pretty robust, but they MUST be kept lubricated on a regular basis. Bachmann like the Annie and Connie will split gears if you look at them crosswise…
Bottom line, I try to weight a loco to scale weight (divide the prototype by the cube of the scale) and so far I do this with impunity on Aristo locos and go a little lighter on USAT and keep them greased.
I’ve left out another variable - traction tires… I am against them, they can put a huge additional strain on the drivetrain, and I found that removing them and using appropriate weights works well.
Regards, Greg
Good sound advice Greg .
Mike Brit
Ok. I have a mix of brands, as many of us do. I did load down my Kalamazoo 4-4-0 with a pound of lead, and she became a great puller. Then one day she stopped on the uphill grade past Shannon. I thought she stalled on some dirty track, but when I went over I could hear the motor still running. When I turned off the power the whole train started rolling backward. Here the axle gear was slipping on the axle, with just enough grab to hold her in place. Kind of like slipping a clutch on a hill to hold a truck in place.
I don’t want to be tearing up gears in my locomotives, but I would like a few of them to haul a bit more then they do. Bill’s concept of ratios may work. Greg I will have to open up the locomotives in question and see what kind of bearings and drives they have. And I do have to get the traction tyre off of the F3.
I know that my Bachmann 2-4-2 is slowly tearing itself apart. I weighted that one down just so it has enough traction to get out of its own way. What a piece of…fine equipment that one is.
Thanks guys.
Anybody have a primer on lubing USAT locos?
Steve, you mean you don’t just dunk them into a pail of 30 weight motor oil?
Steve, no primer, but this may help:
Keep the axle tips that go into the journals very well lubed, you cannot over lube these. very thick oil is my choice, like heavy gear oil.
Grease gets forced out, and light oil does not do it. The bearings will naturally wear the upper part of the bearing… you can turn the bearing in the journal to get more wear from it.
The inner bushings inside the block should have heavy oil also, but you can indeed lube them from the outside. Grease gets wiped off.
The gears themselves usually do well, what often happens is that people open the block and do not reassemble properly, and destroy gears right away, and blame the drivetrain, not realizing they caused the problem.
’
Packing gearboxes with grease just does not work, you want a “clingy” grease. I’m a bit finicky about this (but never have damaged a gearbox or had one wear out)… I use the “gel” greases that cling to the gears and stay on the gear.
Barring that, a good automotive wheel grease with moly in it will really do the trick, the moly sort of plates the gear teeth and cuts friction and wear.
The “floppy” axle in their 3 axle locos does not do much (unless you add weight or spring tension) so it’s not so critical, but open it up every so often and inspect and grease.
Taking off the traction tires allows the wheels to slip when you have excessive load or a derailment, and in my opinion, allows the drivetrain to last longer.
Hope this helps. (also my web pages on USAT motive power)
Regards, Greg
William Seabrooke said:
What is something I can use to add weight to my locomotive?
I am still thinking myself William
Lead, lead shot in bondo, heavier batteries, lots of choices. How about an extra battery to be transferred to when the first one runs down?
Greg Elmassian said:
Steve, no primer, but this may help:
Keep the axle tips that go into the journals very well lubed, you cannot over lube these. very thick oil is my choice, like heavy gear oil.
Grease gets forced out, and light oil does not do it. The bearings will naturally wear the upper part of the bearing… you can turn the bearing in the journal to get more wear from it.
The inner bushings inside the block should have heavy oil also, but you can indeed lube them from the outside. Grease gets wiped off.
The gears themselves usually do well, what often happens is that people open the block and do not reassemble properly, and destroy gears right away, and blame the drivetrain, not realizing they caused the problem.
’
Packing gearboxes with grease just does not work, you want a “clingy” grease. I’m a bit finicky about this (but never have damaged a gearbox or had one wear out)… I use the “gel” greases that cling to the gears and stay on the gear.
Barring that, a good automotive wheel grease with moly in it will really do the trick, the moly sort of plates the gear teeth and cuts friction and wear.
The “floppy” axle in their 3 axle locos does not do much (unless you add weight or spring tension) so it’s not so critical, but open it up every so often and inspect and grease.
Taking off the traction tires allows the wheels to slip when you have excessive load or a derailment, and in my opinion, allows the drivetrain to last longer.
Hope this helps. (also my web pages on USAT motive power)
Regards, Greg
Thanks, Greg.
David Maynard said:
Steve, you mean you don’t just dunk them into a pail of 30 weight motor oil?
Well, I was going to use 40 wt., but if you think that 30 wt. is sufficient… 
Greg, is there any chance that yo could update the photos on this site? Neither LySOL nor AristoCraft dot com exist, any more. Thanks.
One problem that can occur with over oiling the journal bearings (in locomotives and cars) is the the rails can get oil on them. For those of us with healthy grades, that can become a real issue.
Steve, LySOL may be closed, but the pictures still work.
David Maynard said:
One problem that can occur with over oiling the journal bearings (in locomotives and cars) is the the rails can get oil on them. For those of us with healthy grades, that can become a real issue.
Steve, LySOL may be closed, but the pictures still work.
Scroll down a ways, there are big red/yellow boxes where photos should be.
Steve what are you looking at? My LSOL pictures are still on my blog. Thems the only pictures I personally care about
edit: I figured it out. Duh!
David Maynard said:
Steve what are you looking at? My LSOL pictures are still on my blog. Thems the only pictures I personally care about
The LSOL pics are still available. BUT!!! You’ve got to know their addresses. We no longer have access to our “albums” but if you can find the pic in an old thread or know the address, you can still get it.
Case in point. This pic of my car is on LSOL and I can access it because I know where to find the old tread searching the Corvette Forum. But, I can’t see the galleries where its stored and the old link to the gallery goes no where.
