FVM GEVO's run faster than SD70's?

[jdcolombo]

Hi everyone.

I just received my order of 4 of the FVM Heritage SD70 ACe locomotives (Reading, Savannah & Atlanta, Erie, and Virginian) and installed TCS decoders in each. The four SD70 units run nearly perfectly together at the same speed.

BUT . . . the three FVM Heritage GEVO's I got several months (a year?) ago appear to run faster - clearly faster at the top end, from about 2/3 throttle up to full throttle.  They too run nearly perfectly together; they just are faster than the SD's. This isn't a decoder issue, because all the units have the same TCS decoders.

Has anyone else noticed this? I can certainly use a speed table to properly match the GEVOs to the SD70's, but I'm curious as to why this seems to be the case - did FVM use a different supplier for the SD70's? Do they have a different motor? Different truck gearing? Or am I just hallucinating?

John C

[Leggy]

Either a different motor, different gearing (likely) or both.

[learmoia]

Either a different motor, different gearing (likely) or both.

For a MFG that put thought into it.. I'm sure there was a decent amount of design involved in getting locomotives (both 4 and 6 axle) to run at roughly the same speed with the same motor design. 

Something we took for granted that many don't realize the work needed to do it.

With DCC and speed matching, It isn't nearly as big of a deal as it used to be.

~Ian

[Packer]

Perhaps your GEVO's are more "broken in" than the ACes?

Besides, how often will you run them at full speed?

I rarely ever run my passenger train at full speed (odd Kato made their HO F40PH top out at around 76 scale mph). I also turn down the speed in my locos so full power is a fairly realistic top speed.

[peteski]

Either a different motor, different gearing (likely) or both.

LOL!  You pretty much covered every possibility here. Not very helpful.

[jdcolombo]

So I did about 4 hours of break-in running for the new SD70's to match the previous break-in for the GEVO's, and the top end speed is clearly different.   I had to dial down CV5 on the GEVO's to about 170 (from 255) to get the speed to match the SD's above 60% throttle.  In fact, the SD70's seem to max out speed-wise at about 65% throttle.  This is using TCS decoders on a Digitrax Chief system set for 11.5v maximum output to the track.

It's a bit strange - up to 50% throttle, the engines run pretty much at the same speed.  After that, things get wacky.   Not hard to correct with DCC, but I still wish I knew why.  It's almost like the SD70's have a rev limiter on the motor!  But since half-throttle gives me more speed than I need anyway, not a big deal.

John C.

[mcjaco]

I have two Kato P42 that don't run remotely close to each other at any speed.  Not sure I understand the dilemma here.  This is pretty common across all brands.

[jdcolombo]

Not really a dilemma.  Easily accounted for via DCC programming, which has already been done, and now my ESU LokSound-equipped GEVO (NKP 8100) plays very nicely with the Lehigh Valley and Central of Georgia, which in turn play very nicely with the Erie, Reading, Virginian and Savannah & Atlanta SD70 ACe's.

Mostly it was curiosity (which I know killed the cat).   My recent Atlas engines, with their new scale-speed motor, all behave exactly alike.   I can copy a speed curve from my RS3's to my RS11's to my GP7's and they all respond the same.   In fact, all my OLDER Atlas locos with the old supersonic motors also behave the same.   I just wasn't expecting a major variation (minor ones, yes, but not major) from FVM on two models that have what look to me like pretty much the same innards.  But I haven't counted gear teeth or looked THAT closely at the motor - because in the end, it really isn't a big deal.  The engines all run great; they are all now speed matched; and I've run all seven of 'em together in a consist for a couple of hours around the layout.  All is good.

John C.