TUTORIAL BBB wheels with rubber O-rings

[Toastie]

Dear All,

I don’t know whether this makes much sense or not; I know at least two people (including me) who were interested in how to get “grooves” into Ben Fleskes’ BigBenBricks (BBB) train wheels so that they can be equipped with rubber O-rings.

The purpose of running the wheels with O-rings is to (strongly) enhance adhesive forces of engine-powered steam locomotives.

This is supposed to be a brief “tutorial” on how to make grooves into BBB train wheels. TLC has its own new version of large flanged train wheels and they have already such a groove. The Emerald Night (#10194) and the Toy Story Train (#7597) feature these wheels. Now, if you’d ask me, BBB L-wheels are actually nicer in their appearance and color as compared to TLC’s version. And at BBB you can choose many different sizes and colors!

But: BBB wheels (L or XL) don’t have grooves … so for now, we need to make them on our own. Before we begin, here is a figure to explain things more easily:

For BBB L wheels and new LEGO wheels D_W = 31 mm. The red LEGO O-ring (shown in black in the figure) has D_O = 25 mm and W_O = 1.5 mm.

The entire machining process is rather straight forward. All you need is:

1. An O-ring which goes into the machined groove. Make your O-ring choice first and then continue.
   
2. A tool to carefully “grind” the groove into the BBB wheel.
   
3. Some sort of machinery to continuously spin the BBB train wheel for the grinding process.
   

Here are some details:

1) O-ring choice

O-ring width: I’d suggest using an O-ring width ("W_O" in Figure 1) of about 1.5 mm. This is more or less matching the red LEGO O-ring width. The Toy Story Train for example comes with red LEGO O-rings. But you can make your own choices! There are tons of different kinds of O-rings out there; just follow the guidelines below and it’ll work. I further suggest that you choose an O-ring with a smooth circular circumference (well, I guess if that is not the case it wouldn't be an O-ring after all ...).

O-ring diameter: The O-ring diameter should be “slightly” smaller than the wheel diameter. Example: The large LEGO train wheel diameter at the inner running surface close to the flange (see Figure 1, “D_W”) is 31 mm. This is the same for BBB L wheels. The “relaxed” red LEGO O-ring diameter ("D_O" in Figure 1) is roughly 25 mm.

Summary: A 1.5 mm thick, 25 mm diameter O-ring works perfectly well for large LEGO Train wheels and BBB L wheels.

2) Grinding tool = hand file

To actually make the groove you need a hand file. The shape should be rectangular with fine teeth on the short side. Here as an example of a relatively cheap file set (< 10 Euro) I purchased for this purpose:

The width of the file should not be larger than the diameter of the O-ring you are going to use. I’d suggest that you use a slightly smaller width than the width of the relaxed O-ring, since it will loose thickness when stretched onto the wheel. For the red LEGO O-ring, a 1.2 mm file works perfectly well - that was by coincidence the width of my cheap file.

3) Machining the wheel

There are many ways to more or less constantly spin the wheel; you could use a drill press or an M or XL PF motor bed to spin the wheel:

All that is required is a smoothly spinning wheel.

Now we need to make the groove. Switch on the power and …

… slightly press the file against the wheel flange. You don’t want to grind the flange - just feel its resistance. Once you are there, press the file towars the wheel center, but not to the extent that the wheel stops spinning. Making the groove may take some time but you will see the file eventually going into the material. Be patient(!!!) - don’t melt the plastic due to excessive heating caused by going too fast into the material.

From time to time stop and try to get the O-ring into the groove; don’t wrap it all the way around though, it will be rather tough to get the O-ring off again without damage to both, wheel or O-ring:

Once the O-ring is “almost entirely” disappearing in the groove you are done. That is a trial and error procedure. With the 1.5 mm thick red LEGO O rings, my groove is about 1.2 mm “deep”.

And finally, you should remove any ridges by tilting the file about 45 degrees (the angle doesn’t really matter) and let it “run” carefully over the groove. This should be the ideal result:

---

I guess this is about it.

Once you have the O-rings on the wheels, your engine will have strongly increased pulling power – provided the motors are capable of delivering enough torque of course.

Maybe this is worth another thread, maybe not: On my BR23, I needed only two O-rings to get full tractive power although there are six driving wheels. In fact putting O-rings on all six wheels made things worse when negotiating curves; I guess this has to do with increased friction forces. On curves, the inner wheels have to travel far less than the outer wheels, but they are mounted onto rigid axles … but I have also heard that four O-rings worked better than two. Oh well, just try it out. There is absolutely no problem at all running BBB wheels with a groove but without an O-ring – so absolutely no harm is done here. After all, TLC’s large train wheels have this groove as well ...

Good luck and Play Well,

Thorsten

Edited May 20, 2013 by Fugazi
added tags

[exon_from_youtube]

I was picking up the mono rail because of that flaw....

how is the climb rate now on 6" height in a foot come out to be with medium weight cars(say 4 to five of them) Seemed that they slipped a lot to me... but the rubber idea might cure it

Edited November 28, 2010 by exon_from_youtube

[Toastie]

I was picking up the mono rail because of that flaw....

how is the climb rate now on 6" height in a foot come out to be with medium weight cars(say 4 to five of them) Seemed that they slipped a lot to me... but the rubber idea might cure it

I am pretty sure that the "rubber idea" (I pretty much like that phrasing ) will do. What I experienced was that one 9V motor simply could not provide enough torque to handle the grip ... but one PF XL or two PF M motors, and even two 9V mini-motors will simply carry you away ...

Rock on,

Thorsten

[Teddy]

Hi Toastie,

thanks for putting this up! It was an extremely helpful tutorial, when I was making the grooves in my BBB-XL wheels.

With the O-rings on, it works like a charm.

Kind regards,

Teddy

[roamingstop]

Thanks - exactly what I wanted as I have an BBB model which has too much wheel spin. A christmas topic.

[locoworks]

i would suggest that O rings are only fitted on ONE side of a loco, this means that on the corners where really bthe wheels should rotate at different speeds the non O ring side is free to skid easily. this will prevent the strains associated with O rings on both sides. ideally eack driving axle should have a diff in the middle and then O rings all round would be OK.

[Toastie]

i would suggest that O rings are only fitted on ONE side of a loco, this means that on the corners where really bthe wheels should rotate at different speeds the non O ring side is free to skid easily. this will prevent the strains associated with O rings on both sides. ideally eack driving axle should have a diff in the middle and then O rings all round would be OK.

Hi locoworks,

that sounds brilliant to me. I was thinking about this before but never tried it out. So now that you brought this up, I need to check. Will report back ...

Thanks a lot!

Regards,

Thorsten

[locoworks]

Hi locoworks,

that sounds brilliant to me. I was thinking about this before but never tried it out. So now that you brought this up, I need to check. Will report back ...

Thanks a lot!

Regards,

Thorsten

i play with 5 inch gauge stuff ( not lego, i wish they would scale up the technic stuff to 'dublo' size ) and for the coning on wheels to work you can only use gentle curves ( like full size stuff ) the coning effectively makes the outer wheel with its flange to the railside slightly bigger in diameter than the inner wheel running on the smaller end of the cone so it wants to turn. trains 'squeal' at slow speeds when the radius is too tight for the coning to work. with the radius of lego curves and the gauge used the difference in distance on each rail in the corners is VERY signifficant and needs a lot of slipping to allow the wheels to take the corners. with O rings all round slipping is hard to achieve and the motor struggles.

[Duq]

That bit about the coning of train wheels is very interesting. Never realised that...

[LEGO Train 12 Volts]

i would suggest that O rings are only fitted on ONE side of a loco, this means that on the corners where really bthe wheels should rotate at different speeds the non O ring side is free to skid easily. this will prevent the strains associated with O rings on both sides. ideally eack driving axle should have a diff in the middle and then O rings all round would be OK.

With the old 12 volts train track put the o-rings only on one side it's not so usefull: if the wheels with o-rings are in the inner side of the curve the loco have not enough grip to complete the circle. I suggest to put o-rings on both sides for the 12 volt's era fans.

Very nice topic by the way!

[Helmantel]

With the old 12 volts train track put the o-rings only on one side it's not so usefull: if the wheels with o-rings are in the inner side of the curve the loco have not enough grip to complete the circle. I suggest to put o-rings on both sides for the 12 volt's era fans.

Very nice topic by the way!

The curves of 4,5 V and 12V track have ribs only on the outer rails (and the inners are smooth), which allows some slippage.

[Toastie]

That bit about the coning of train wheels is very interesting. Never realised that...

Actually, I >just< got it! Me too, I never realized the coning to be that important - well actually I did not think about the coning of the train wheel treads to be of any particular value at all! Just wondered why BBB wheels have such a steep "coning". Thanks Duq that you pointed expressively to "coning" - I completely missed that in locoworks post.

And thanks to locoworks that you showed the coning to be such a crucial thing (in real world that is, not with respect to the way too tight LEGO track curves)!

Well, I have learned a lot in this thread. Eurobricks rocks!

I don't know whether this is of any particular value, but here's a link on "coning" that I found really helpful.

Regards and thanks again to all,

Thorsten

The curves of 4,5 V and 12V track have ribs only on the outer rails (and the inners are smooth), which allows some slippage.

Learning, learning, learning ...

never even thought about that. Well, I don't have any 4,5/12V tracks now (@ age 48) but used to have a couple then (@ age < 14 years). Back then I guess I wouldn't have realized that at all, now it seems to be the obvious ... and so brilliant!

Thanks for the inspiring post!

Thorsten