Transmissions,

[garethjellis]

Had great fun at a show during the last weekend passed. I had some interesting problems with some of the transmissions on my models.

The first issue is that i used two bevel gears that under the torque from the L motor kept on pushing apart, secondly the torque of the bogey was causing the bogie to twist hard and to derail on a curve, even at low speed.

So I wanted to start a fresh thread, people can share their transmission ideas, weather tried and tested or just ideas would be great.

Thanks

here is one of the transmissions in question that pops the red 1x4 off the bottom.

Edited December 2, 2014 by garethjellis

[Stefaneris]

Hello

Have you considered changing the red and some other bricks with this brick?

I know you would have to change the ends of the boogie, but I tried this solution with one of my trains where I had the same problem and it worked. Another solution would be to add plates but then you might have problems with driving over switches

[jtlan]

It's usually better to build these trucks using Technic frames, to avoid the popping-out problem you described.

As for the sliding bevel gears, any time gears are used the inter-gear forces will tend to separate the gears (this is a consequence of compromises made in the shape of the gear teeth). This is why it's important to properly support gears; in the case of bevel gears, they should have a solid surface behind them. Try using the double bevel gear, which should fit in the space between the 20-tooth bevel and the technic beam.

As for the derailing problem, I believe one of the Railbricks issues talks about how you might mitigate it. I suspect the problem is magnified by the fact that you have a 20:12 gear-up inside the bogie; the effect would be reduced if this gear-up was done inside the locomotive, and the entire bogie was built with 1:1 gearing.

[greenmtvince]

This is the basic design I'm using on the trucks for the tender of my 2-10-4:

IMG_7301 by Cale Leiphart, on Flickr

Works really well in all the testing I've done so far.

[legoman666]

I use a modified version of the bogie in the railbricks magazine. No problems on turns with stock lego wheels. The 1x1 bricks /w 1 stud that are connected via their top stud to the center of a 2 x 6 plate like to pop out though. It's especially a problem on older 2x6 plates.

How much weight do you have over the boiges? Also, the amount of internal friction could cause the entire bogie to want to spin rather than rotate the wheels. Try putting a drop of oil in the axle holes.

[peterab]

There is an article in Railbricks which describes a ridge on the inside of 9V track which may cause derailment with powered bogies. The article describes how you should design your bogies so the torque turns them away from the ridge. In practice just running in the opposite direction may help.

[Exa]

Far far ago, I got an HO train. It was using endless screw to bring power from central engine to each bogies. On the down side, it needs much more gears in the bogie. I dont know if such a system can be used with Lego.

[cgarison]

As far as preventing the issues of the torque pushing the bevel gears apart, I use a slower 1 to 1 gear ratio in my trucks to keep the speed of the train down and to reduce the stress on the plastic gears when trying to move heavy mass with light weight plastic running gear. By not trying to "speed" up the train using the gearing in the trucks, I get much longer running time and much less stress on the train. The bogeys that I run are a clone of those that are under Peter Morris's Space Train with some additional plates on the bottom to provide support and prevent issues from parts losing their clutch too quickly.

I can't solve the override issue on the bogeys twisting and jumping the rails as I have had that problem on a layout earlier this year and I have to place the majority of the blame for that set of incidents on the uneven surface of the tables that out layout was built. It was just something that could not be avoided. We had to watch the train running on that layout very carefully the whole weekend. I did receive some of the best advice around our weekend of issues from Robin at GFLUG. He told me to make sure you have plenty of support for the axle (motor shaft) coming out of you motor and going into your trucks to provide stability for the running gear. In my latest creation, I have 3 technic plates plus the round 4X4 plate setting on the turntable between the bottom of the L-motor and the end of the shaft at the plates. This design proved extremely robust and I ran my Ghost Train MOC for 3 days a couple of weeks ago without a single issue from the running gear and without the over run issues that plagued our layout in VA. Not sure if the extra plates helped with the over runs, but I am certain that I ran that train with much less wear and tear on my locomotive than I have experienced in the past two years.

One thing that I have learned is that I would rather make a train MOC that is robust and not quite as pretty if I intend to run it for a weekend than skimp on the plates to provide structural support and then have to deal with a train that periodically disassembles itself as it runs around the track. If needed, I can make it pretty for pictures on my Flickr page and then build it mechanically solid to run on the layout at an event.

[dr_spock]

I put technic bushing on my axle to keep the adjacent gear from popping out the end of its axle.

[zephyr1934]

Indeed, it sounds like you are dealing with two or three problems...

I put technic bushing on my axle to keep the adjacent gear from popping out the end of its axle.

Spot on, in addition to the force trying to push the truck apart, the bevel gears will want to creep off the end of the technic axles if they are able to. Putting a bushing in the way so that there is nowhere to go is quite helpful, or in the case of the following picture from an earlier post, a pin connector on the central axle and 1x1 technic bricks on the cross axles. Given the fact that there is an XL motor in the background and this is Cale's design I would surmise that it is plenty sturdy.

This is the basic design I'm using on the trucks for the tender of my 2-10-4:

IMG_7301 by Cale Leiphart, on Flickr

Works really well in all the testing I've done so far.

There is an article in Railbricks which describes a ridge on the inside of 9V track which may cause derailment with powered bogies. The article describes how you should design your bogies so the torque turns them away from the ridge. In practice just running in the opposite direction may help.

Yes, and a quick summary can be found here. Though that discussion was why you will likely have better performance running your steam engines clockwise (rather than counter clockwise) around a 9v layout.

A similar problem arises in how you choose to transfer power to the wheels. If the central axis is spinning clockwise as the train goes forward it will push the front axle of the truck against the right hand rail and it will hit the small protrusions at the rail joints. Rebuild your truck swapping the location of at least one bevel gear and now the central axis will have to turn counter clockwise to go forward, thus pushing the leading wheel against the left rail, away from the protrusion at the rail joints (I THINK the RB article goes into more detail on this problem, see in "Clockwork" in RB 7 for more info).

[dr_spock]

I put technic bushing on my axle to keep the adjacent gear from popping out the end of its axle.

I think a pic is better than words.

A bushing can also be added to the center bley axle if the center gear is popping out. I didn't have that problem. Just the gears on the ends that fall out from time to time and leave the engine stranded.

[cgarison]

Just the gears on the ends that fall out from time to time and leave the engine stranded.

Use black Technic axles that are cut down to the precise length you need and make sure you have nice square edges for the gear to attach at the end of the axle. This stopped my gear popping off issue on trains.