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Finescale loco wheels on O gauge Peco Bullhead Track


ianbr
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I have built the Connoisseur Models starter loco kit and used the recommended Slaters finescale wheels 7842W.

The width of the axles and wheels on the Peco bullhead track appears to be too small and is giving electrical drive problems as the engine moves from side to side when going along the track.

Is this a common problem with finescale wheels and should I purchase a different type in order to solve the problem?

Any help would be most welcome

Many thanks

Ian

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How much float is there between the rear of the wheels and the frame? Too much can cause what you describe, and can be cured by putting thin washers around the axles behind the wheels. If it’s an 0-4-0, it should need only a fag paper of clearance to allow the axle to float along its length.

 

The kit may have narrow frames to permit use of coarse-scale wheel-sets, which have a smaller back-to-back.

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Hi Nearholmer

 

Many thanks for your response.

 

I have finger tightened the machine screw for the crankpin as far as possible as I have noticed that loose 'wobbly' wheels create electrical pick up problems.

 

So I don't believe there is any float as you describe.

 

I will try the washer idea.

 

So are you saying that coarse scale wheels have a narrower gauge width than finescale?

 

Apologies, I am new to this scale.

 

Thanks

 

Ian

 

 

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Coarse scale uses a thicker flange, but the gauge of the track is the same (32mm), so the distance between the backs of the wheels is smaller.

 

I can’t off-hand remember what the b-t-b is for finescale (29.5mm??) because I run coarse scale, and set my point-work to operate with a b-t-b of c27.5mm (over the years, coarse scale used multiple different b-t-b figures, so what I use is a compromise dimension).

 

Are your wheels loose on the axles? Or, out of square on the axles? I ask because the crank pins shouldn’t have a lot to do with all this.

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Slaters wheels are at the narrower end of the Finescale standards. Short wheelbase locos are liable to 'crab' slightly because of the amount of slop between the wheels and rail. The narrower wheels available these days are also likely to get wheeldrop while going through point frogs. A growing number of people are moving towards 0MF track standards with a narrower track gauge of 31.5mm which cures both these problems.

 

Edited by HSB
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Could you post a couple of photos of the frames up one from above and one from below, just to help us.

 

Did you clean up the square end of the axles?

 

Have you tightened up the Allan screw with a Allen key?

 

The end float between the wheels and the bearings in the frame want to be as small as possible.

 

The questions could go on, that's why a photo or two can help.

 

OzzyO. 

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Hi Howard

 

I think you are correct in it being due to the amount of slop between the wheels and the rail. I also suffer from wheeldrop on the peco bullhead points.

 

Its too late for me to change track standards as I have gone all in with Peco bullhead.

 

Nearholmer above says coarse scale wheels have wider flanges but the backs of the wheels are closer together which means even more slop between the wheels and the rails?

 

Moving to coarse scale wheels does therefore not appear to be the answer and in fact could give even more problems. Please confirm I have understood this correctly.

 

Just to answer some of the above questions:

 

The wheels are not loose on the axels or out of square and have been lightly tightened using an allen key.

 

The end float is as small as possible.

 

Thin washers around the axels behind the wheels appears to be the next step.

 

Many thanks for all your help

 

Ian 

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48 minutes ago, ianbr said:

Nearholmer above says coarse scale wheels have wider flanges but the backs of the wheels are closer together which means even more slop between the wheels and the rails?


No. The gauge is still 32mm.

 

Coarse scale standards work in a different way, by having a wide wheel tyre, so don’t suffer ‘frog drop’.

 

But, I wouldn’t recommend coarse scale standards unless, like me, you collect 1930s and 1950s models, because everything these days is designed for finescale standards, and most people value appearance - coarse looks a bit coarse.

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Unfortunately, there is no solution to the gauge/wheels problem other than using 31.5mm gauge. However it is probably because the loco is an 0-4-0T, an 0-6-0 would not be such a problem. 0-4-0s will always have a tendency to do this if the wheels axles etc are not absolutely perfectly aligned.

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Does`nt matter whether it`s an 0-4-0, 0-6-0, 0-8-0.....

 

If the chassis is square and the wheels are not wobbly and the electrical pickups are the right type and positioned in the right place on the backs of the wheels an 0-4-0 will run perfectly well on Peco track......

 

 

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I have found that especially with 4-coupled locos there is a need to ensure that the axles are an easy sliding fit in the bearings (sloppy often) and the same with the rods on the crankpins. This helps stop any tendency for the chassis to get pulled sideways back and forth on the axles as they rotate and so give the well known waddle. Excessive sideplay obviously doesn’t help but isn’t always the only culprit.

Edited by Izzy
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An easy sliding fit Izzy, everytime, but sloppy fit never it will only end in tears when you progress to valve geared 0-4-0`s.

 

A guaranteed method of simple chassis construction every time is to assemble the coupling rods first drilled to suit your chosen crank pin bearings.... and use them to accurately line up everything else...

DSC05979.JPG.6b0fb12ec88d90096c4086e65905a583.JPG

 

If you sloppy everything up at this stage you will be bu*^""$ed when you add other trappings....

 

 

 

 

 

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If the wheels are correctly seated on the axle shoulders and are running true I would suggest checking that your coupling rod centres are exactly the same as your axle centres as Rosspop describes. Apart from 'crossing drop' (which most people just live with) you shouldn't have a problem with Slater's wheels on Peco track as this is probably the most commonly used combination used by 7mm scale modellers.  Best of luck.

Ray.

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I completed this kit a few months ago so perhaps I can assist.

 

I added several washers between frame and wheels to reduce the sideways axle travel to ~0.7mm. The loco runs fine through tight curves with no binding or waddle.

 

If you have excessive sideways axle travel your plunger pickups may lose contact with the wheels. Check that your plungers are free to travel through their full range of motion. 

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"Just to answer some of the above questions:

 

The wheels are not loose on the axels or out of square and have been lightly tightened using an allen key.

 

The end float is as small as possible.

 

Thin washers around the axels behind the wheels appears to be the next step".

 

In the above quote from one of your posts you mention the end float is as small as possible but you then mention about washers around the axle behind the wheels. If you have no end float between the wheels and bearings how are going to fit them?

 

As I mentioned before a photo or two could help us help you a lot more.

 

OzzyO.

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2 hours ago, ozzyo said:

In the above quote from one of your posts you mention the end float is as small as possible but you then mention about washers around the axle behind the wheels. If you have no end float between the wheels and bearings how are going to fit them?

 

I think the word "float" is being misinterpreted.

 

We are talking about the gap between wheels and frame but from the earlier response I get the impression that the OP took it to mean wheels moving on the axles.

Edited by Hal Nail
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On 04/01/2022 at 18:21, ianbr said:

Hi dpgibbons

 

Thank you confirming the washers work.

 

Would you mind letting me know how many you used and their size.

 

Regards

 

Ian

 

 

Three thin brass washers, from Slaters I believe. Thickness unknown but you can calculate what's required for a ~0.7mm axle slop.

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Have you thought of trying the Slaters 31.2mm B to B axles instead of the 29.2mm B to B ones.

I suppose you have checked the back to back on the wheels is correct? (29.2)   00 Romfords can be tight to gauge if you mix and match the wrong ones and they have similar squared axle ends.

Edited by DCB
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11 hours ago, Marshall5 said:

I think we are getting confused here.

As I have said many times, when asking a question on rmweb, it is consideraby easier to sift through the suggestions if you already know the answer!

Edited by Hal Nail
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The OP seems to be complaining about the wheels being tight to gauge

 

On 03/01/2022 at 07:42, ianbr said:

 

Just to answer some of the above questions:

The wheels are not loose on the axels or out of square and have been lightly tightened using an allen key

The end float is as small as possible.

Thin washers around the axels behind the wheels appears to be the next step.

Many thanks for all your help

Ian 

Hench my suggestion

I suppose you have checked the back to back on the wheels is correct? (29.2) 

 00 Romfords can be tight to gauge if you mix and match the wrong ones and they have similar squared axle ends.

(If so)  Have you thought of trying the Slaters 31.2mm B to B axles instead of the 29.2mm B to B ones.

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