RTR locos and finescale track

[Fiacra]

Hi folks,

I was under the impression that the wheels on modern RTR locos are likely to be compatible with most types of track - apart from P4 standards. However, I've tried running a MM 121 on Marcway SMP code 75 bullhead flexitrack and Exactoscale bullhead basses with the same SMP rail. In both cases, there's a very obvious 'thunk, thunk, thunk, thunk....' sound as the loco runs along the track. Evidently, the wheel flanges are hitting the chairs. Has anybody out there replaced the wheels on their IRM and MM locos with finescale alternatives, without going all the way to P4 tolerances? 

[Noel]

58 minutes ago, Fiacra said:

Hi folks,

I was under the impression that the wheels on modern RTR locos are likely to be compatible with most types of track - apart from P4 standards. However, I've tried running a MM 121 on Marcway SMP code 75 bullhead flexitrack and Exactoscale bullhead basses with the same SMP rail. In both cases, there's a very obvious 'thunk, thunk, thunk, thunk....' sound as the loco runs along the track. Evidently, the wheel flanges are hitting the chairs. Has anybody out there replaced the wheels on their IRM and MM locos with finescale alternatives, without going all the way to P4 tolerances? 

I've had no problems with MM 121 or 141 running on Peco code 75 track. Apologies I have no experience running on other track systems.

[David Holman]

Surprised to read of your issues. Older Lima stuff certainly has deep flanges that require code 100 rail, but current models should be fine on code 75. Might be worth carefully checking all wheels, just in case a bit of crud is causing the problem. Likewise, if the track has been blasted maybe it needs checking too?

[Noel]

On 22/6/2024 at 5:14 PM, David Holman said:

Surprised to read of your issues. Older Lima stuff certainly has deep flanges that require code 100 rail, but current models should be fine on code 75. Might be worth carefully checking all wheels, just in case a bit of crud is causing the problem. Likewise, if the track has been blasted maybe it needs checking too?

Yes only old Lima stuff with the pizza cutter wheels couldn't run on code 75 

[StevieB]

My two Lima class 201’s would run quite happily on code 75 Peco streamline track.

Stephen

[Fiacra]

It's interesting to hear that there are no issues running on Peco bullhead code 75 track. I wonder if, despite both being labelled 'code 75', there are some dimensional differences between Peco and SMP rail/chairs. I came across a post on Rmweb a while back in which a poster claimed that Peco bullhead track is not 'finescale'. This would suggest some differences - and I'm pretty sure he was not talking about the gauge, given that some OO gauge layouts are billed as finescale (handmade track etc). 

[Broithe]

On an old 00 layout, with code 100 track, we had one old loco which would clatter on the chairs of one particular set of points.

The loco got through other, apparently identical, points without any issue. And no other vehicle had an issue at those points.

It was probably just a tolerance issue - I suspect the rail was a touch undersize.

I 'fixed' the issue by grinding almost nothing off the flanges.

It may even have only occurred on one side of the vehicle, or one rail, but I did the wheels on both sides before I thought of that.

Edited July 3 by Broithe