Gear ratio

[petdrus]

Hi guys.  Re: item 83904, Spectrum series HO N&W 4-8-4 Class "J" pass loco.  Beautiful loco, but does not have the grunt to pull the "Powhatan Arrow" on her own.  I wish to motorise either the "Canteen" (Spectrum item 89922) or the bagage car I have for that train, "chip it" then run them as a consist.  To do this properly, I need to know the gear ratio used in the Spectrum Class "J"  THX

[pdlethbridge]

If you are doing this in DC, you'll need the gear ratio, but if you are doing this in DCC, you can program the decoder to match speeds.

[jonathan]

Petdrus,

By lack of 'grunt', do you mean the drive wheels start to spin on the rails, or does the locomotive stall?

If you are getting wheel spin, perhaps a coating of bullfrog snot will help.  By coating just one wheel, I have been able to greatly increase pulling capacity without detrimental affects to current pick up nor overtaxing the motor (so far).  This may be a more economical (and easier) method than powering a car, plus the added expense of a decoder.  

Even cheaper, but a little more work, is adding weight to the locomotive.  A couple ounces of lead, properly placed in the boiler, can work wonders.

If the locomotive is stalling, then a powered car would be helpful.  As PD wrote, gear ratio is probably moot in DCC.  One can program to match speeds.

Not a sermon, just an opinion.  

Regards,

Jonathan

[JerryB]

I don't understand why you need the gear ratio for the locomotive. Certainly any motor you choose will have different voltage vs shaft speed (RPMs) than the locomotive's motor and the proposed  'helper car' will have different diameter wheels than the locomotive. Since the need is to match the linear distance traveled by the locomotive and the 'helper car' at the same voltage, those two factors make the gear ratio of the original locomotive irrelevant.

Your 4-8-4 should be able to handle a reasonably sized consist, especially using large radius (~22" and larger) curves, and fairly level track (<2% or <1 in 50 grades). In addition to the suggestions made in the above posts, what is your ruling gradient? How many cars are you trying to pull? Also, have you serviced all the cars to ensure that they are free rolling? A pass with a truck bearing reaming tool followed by a puff of graphite lubricant in each axle bearing can make a world of difference.

If the above suggestions don't provide the operation you are looking for, then adding a powered helper might be in order. You could start by determining the voltage vs speed ratio for the locomotive when it is operating under load. Using the diameter of the wheels on the proposed  'helper car,' determine what axle speed (RPMs) will provide a close match, then work out a motor plus gearbox ratio that will give something close to that axle speed. You mention 'chipping' the helper car, so I assume you are using DCC. If that is the case, the final match can be made by programming the DCC as Jonathan suggested.

Hope this helps,

Happy RRing,

Jerry

[petdrus]

THX Guys.  The "Powhatan Arrow" was a large train for N&W.   My layout has a 1.5% grade, so my "J" tends to stall on the upside.  I live in the land downunder, so not sure what bullfrog snot is.  Sounds great though!!  Kinda knew about the DCC bit, just do'n the homework beforhand.  Done the extra weight thingy, no good.  Tested my theroy chipping a switcher using it as as pusher, will need to add weight into the tenders.  To motorize the canteen, to hard, to small.  To motorize the bagage car will be a lot easier, a good way to deguise the extra motive power!!!  Will film and youtube this for you all when done.  THX again guys. petdrus

[Doneldon]

pet -

I think we can offer some additional help if you tell us whether your problem is that the J's wheels spin on the grade or the whole thing grinds to a halt with no wheel spin and no forward motion.

                                                                         -- D