Gearbox Help Needed

[yoraish]

Hi, recently I was trying to improve my Tatra truck and learn some more about gearboxes by building a 3 speeds gearbox into the truck. Now the gearbox works marvelously good but the 2nd gear does not. When I switch to the 2nd gear it crackles and clicks. I guess I should reinforce it more but I don't know how to do this without extending its length too much. Any suggestions?

This is the gearbox:

*The yellow liftarms are part of the trucks chassis.

*The LDD file is HERE.

Thanks!

[SNIPE]

the worm gears and several gears in a row along the top is a bad idea and you can use a gearbox like on the 844 super car, its small and compact and can have several speeds. (this is in the LDD file)

this is not what you asked in the topic so my guess is that your gears are either too small (too little friction therefore little torque or too big (too much friction and torque) so use some gears that have a few more/less teeth or find another way which they might mesh better (IE some holes might be too far or too close which causes the gears to slip when in the meshing process, also if they are too slack you can wear the teeth down and if they are too tight you can snap the gear in half or wherever.

if this still isn't the case then you can keep these meshed by having a tight pulley inbetween the two gear axles,this is good because the pulley can be tight when it needs to be and it can also loosen up slightly in the meshing process if the part or placement is changed.

another way is have a beam with holes in it in both sides of the gear (with the axle(s) going through BOTH the beams)

also make sure your gears are not counter rotating to their natural rotational direction, this means that they can jam or slip away from each other (and not mesh), your motors and the gears outputted from it might not be syncing properly (one shaft or gear+shaft might be spinning slower or faster or in the wrong direction to another shaft or gear+shaft coming from another motor.

there are many other problems which in that case you might have but i cannot explain all of them.

Edited April 21, 2011 by SNIPE

[yoraish]

the worm gears and several gears in a row along the top is a bad idea and you can use a gearbox like on the 844 super car, its small and compact and can have several speeds. (this is in the LDD file)

this is not what you asked in the topic so my guess is that your gears are either too small (too little friction therefore little torque or too big (too much friction and torque) so use some gears that have a few more/less teeth or find another way which they might mesh better (IE some holes might be too far or too close which causes the gears to slip when in the meshing process, also if they are too slack you can wear the teeth down and if they are too tight you can snap the gear in half or wherever.

if this still isn't the case then you can keep these meshed by having a tight pulley inbetween the two gear axles,this is good because the pulley can be tight when it needs to be and it can also loosen up slightly in the meshing process if the part or placement is changed.

another way is have a beam with holes in it in both sides of the gear (with the axle(s) going through BOTH the beams)

also make sure your gears are not counter rotating to their natural rotational direction, this means that they can jam or slip away from each other (and not mesh), your motors and the gears outputted from it might not be syncing properly (one shaft or gear+shaft might be spinning slower or faster or in the wrong direction to another shaft or gear+shaft coming from another motor.

there are many other problems which in that case you might have but i cannot explain all of them.

Thanks! But I'm afraid most of the potential problems you stated are not relevant. You mentioned that placing a vertical liftarm that will hold both axles together will fix the problem, and I agree. But where can I place it so it would no change the length of the gearbox?

[SNIPE]

Thanks! But I'm afraid most of the potential problems you stated are not relevant. You mentioned that placing a vertical lift arm that will hold both axles together will fix the problem, and I agree. But where can I place it so it would no change the length of the gearbox?

if you have bushes you can remove them or use a half bush and use either a lift arm or a half size lift arm, you could use a thinner gear and another thinner gear (even bevel gears work as normal gears (not on an angle))

you could use a part which does the same job but takes a little bit of space off the old part, just try and use your imagination to fix the problem that you created then you will learn and be a better builder

if you can give me a LDD file of only the gearbox i think i could make it better.

Edited April 22, 2011 by SNIPE

[yoraish]

Hi, first of all thanks for your reply. I have put a wrong LDD file on the original post so HERE is the file for the gearbox only. And what do you mean by thinner gears? I don't think they exist.

[SNIPE]

Hi, first of all thanks for your reply. I have put a wrong LDD file on the original post so HERE is the file for the gearbox only. And what do you mean by thinner gears? I don't think they exist.

the pinion gears are thinner but can be used not at an angle, like normal gears

[yoraish]

the pinion gears are thinner but can be used not at an angle, like normal gears

But the overall space both of the gears use is 1 stud so it doesn't matter as to reinforcing the gearbox.

[nielsvdv]

i would try this

if u want strenght, u can try to rebuild the module with long axles and connecters with holes for the driveschaft. this replaces the long beams, who can bend more and are harder to stay in alignment with other beams by using only few studs.

like i dit in my tatra, the whole gearbox is made with long 9l axles and connecters, these are like beams, if u build 2 of those u can connect them with 3l plater (don't know in english, 1x3 xox holes). these wil stay very rigid.

for the sliding i would suggest making an axle rail. just 2 axles in the lenght, where the gearbox can slide on using connecters.

maybe this can help. if u don't understand the whole axle and connecters gearbox idea, just go to my tatra instructions and u will find the gearbox pic.

regards

niels

[yoraish]

Thanks for your comment but I'm talking about a very specific problem which is the gears slipping in the 2nd gear.

[nielsvdv]

Thanks for your comment but I'm talking about a very specific problem which is the gears slipping in the 2nd gear.

well, i havent looked at the file, only the pic. but i think it is probely the beams that are just not perfectly aligned. a second gear out of 3 has to take the most stress because it is the middle one.

and why i didn't look at the file, i don't like building lego on the screen. lego should keep the kids away from that all powerfull lightbox :)

niels

[AndyC]

Hi, first of all thanks for your reply. I have put a wrong LDD file on the original post so HERE is the file for the gearbox only. And what do you mean by thinner gears? I don't think they exist.

I might just be being very dense, but I can't work out how that's supposed to change gears or where the output from the gearbox is supposed to be.

[DLuders]

@ Yoraish: I opened your latest LDD Gearbox .lxf file, and twirled it around to see the various gears at the best angle. I see that there is room to insert two Technic Bushes (pictured below) on each of the two 10L axles coming from the center of the two PF XL motors. If you add these Technic Bushes to your real gearbox model, the 16-tooth (16z) gears won't have a chance to slide down the axle, and it will be forced "tight" against the Technic Liftarm.

There is also room to insert a Technic Bush on the underside of the gearbox, on the 6L Axle that is between the two 20-tooth (20Z) Double-Bevel Gears.

You have an advantage in that you have the PHYSICAL MODEL in your hands, and it's easier to see what's going on with the gears than it is viewing it in LDD. If there are any other "exposed" axles, add additional Technic Bushes so that the adjacent gears and Liftarms do not slide or flex.

[SNIPE]

@ Yoraish: I opened your latest LDD Gearbox .lxf file, and twirled it around to see the various gears at the best angle. I see that there is room to insert two Technic Bushes (pictured below) on each of the two 10L axles coming from the center of the two PF XL motors. If you add these Technic Bushes to your real gearbox model, the 16-tooth (16z) gears won't have a chance to slide down the axle, and it will be forced "tight" against the Technic Liftarm.

There is also room to insert a Technic Bush on the underside of the gearbox, on the 6L Axle that is between the two 20-tooth (20Z) Double-Bevel Gears.

You have an advantage in that you have the PHYSICAL MODEL in your hands, and it's easier to see what's going on with the gears than it is viewing it in LDD. If there are any other "exposed" axles, add additional Technic Bushes so that the adjacent gears and Liftarms do not slide or flex.

i seen this also after removing everything but the gears and the axles for the gears.

also, i would not use two big motors like that, another question is, how does it change gear? i seen no mechanism there to do so.

[yoraish]

i seen this also after removing everything but the gears and the axles for the gears.

also, i would not use two big motors like that, another question is, how does it change gear? i seen no mechanism there to do so.

Again, my problem is not the gears going sideways. It is the gears that don't mesh good enough and slip. I will add a video later today to show the physical problem and the switching mechanism.