Blind drivers

[hoppercar]

Are blind drivers normally wider that the rest of the driving wheels, or the same width ??

[Fender]

Yes, they need to be wider, to prevent the inside edge of the driver tire from dropping off the rail on a curve, since there is no flange there.

[STRR]

They were both same width as the flanged driver (without the flange) AND they were wider than the flanged driver. It depends on which railroad was using them, on which class locomotive, and on what route. Blind drivers were used to allow longer wheel based locomotives to negotiate shorter radii curves. On routes with very short radius curves there may be more than one set of blind drivers and/or wider blind drivers to negotiate the curve. The wider drivers would have to be built to maintain adequate clearances between the drivers and the frame components.

On some later models, the drivers had a lateral motion device that would allow the axles to slip sideways a bit.

[cbrew]

for the scale locomotive. there is no need to go wider, the thread is wider only because the flange was removed
this is a shot from my Allen ten wheeler, it was able to handle a 25 foot curve with out issue

[hoppercar]

Does the blind wheel have the usual 2 degree taper, or is it turned flat without a taper ?

[cbrew]

Does the blind wheel have the usual 2 degree taper, or is it turned flat without a taper ?

a friend of mine shared this out of an old engineering book,
I followed this spec

[GO&PRR]

FYI - do a search for 'Blind Driver' in this Live Steam group and you will find many threads devoted to this subject with good answers.
Example thread "blind driver
Post by hoppercar » Sun Sep 15, 2019 3:41 pm"
May want to do same search in the Riding Scale Railroading as well.
Have been going through past notifications and this subject has been turned many times.

[makinsmoke]

The Santa Fe 940 2-10-2 in Bartlesville has blind center drivers. They are the same width as the flanged drivers, and are tapered as per the diagram above.

Still, the leading and trailing parts of the frames where the front and rear drivers ride have very noticeable grooves in them where the drivers cut into them negotiating sharp radius track.

The sound must have been unreal.

[Pontiacguy1]

for the scale locomotive. there is no need to go wider,

I will have to disagree in certain cases, although it may work fine for your 2-6-0 or a consolidation or something. My 2-10-0 has a blind center driver that is currently the same width as the other drivers. If I am going around a fairly sharp curve (probably 50 to 60 ft radius), and there is a slight kink at the rail joiner on the outside rail, then it will sometimes fall in behind the outside rail. It doesn't do it very often, but I have had it do that on multiple occasions, so it can be a problem. One particular spot that I can recall, it would run fine during the morning, then when the afternoon sun heated up the track, it would start falling in at a particular spot. Once the sun began to go down, it stopped doing it again. Tells me that it was pretty close to begin with.

I am going to put a tire on that driver that is wider than the other drivers to make sure that this doesn't continue to happen in the future.

My advice to anyone would be to look at the wheelbase of your locomotive and decide based on that. The longer the wheelbase is, the wider the blind tire will likely need to be to keep from having issues.

[cbrew]

for the scale locomotive. there is no need to go wider,

I will have to disagree in certain cases, although it may work fine for your 2-6-0 or a consolidation or something. My 2-10-0 has a blind center driver that is currently the same width as the other drivers. If I am going around a fairly sharp curve (probably 50 to 60 ft radius), and there is a slight kink at the rail joiner on the outside rail, then it will sometimes fall in behind the outside rail. It doesn't do it very often, but I have had it do that on multiple occasions, so it can be a problem. One particular spot that I can recall, it would run fine during the morning, then when the afternoon sun heated up the track, it would start falling in at a particular spot. Once the sun began to go down, it stopped doing it again. Tells me that it was pretty close to begin with.

I am going to put a tire on that driver that is wider than the other drivers to make sure that this doesn't continue to happen in the future.

My advice to anyone would be to look at the wheelbase of your locomotive and decide based on that. The longer the wheelbase is, the wider the blind tire will likely need to be to keep from having issues.

Morning,
Couple questions
how much wider will your frame allow? (adding to the back side), unless the frame is narrowed a bit, i cant see adding any real width to the tread.
I do see you are talking about dropping behind the outside rail.
is the center the only blind driver?
what diameter drivers does this locomotive have?

[Pontiacguy1]

7" drivers, 36" rigid wheelbase. #1 driver and #5 driver have full flanges. #2 and #4 drivers have thinned flanges, which are about 0.050" thinner. center driver is blind, but same width as the other drivers. I do have some room behind the driver, and I'm going to add about 0.100" on the outside and probably about 0.060" behind the wheel. Will used a stepped tire this time so that I have a shoulder to put it against.

[Fender]

An alternative to a completely blind driver is to make the flange on the center driver(s) with a narrower and shorter profile than the others. This gives a similar effect as providing lateral motion on the center drivers. This “mini-flange” was sometimes used on narrow-gauge engines that encountered sharp curves.