[WIP] Volvo EC750E

[cloud]

A different track related question is which wheel looks better for the front free spinning wheel/sprocket?

I'm inclining towards the wheel in the middle as it is 3 studs wide whereas the tire is 4 and the wheel on the right is 5.

[1gor]

I think first one is the best 

 

[cloud]

While I wait for the wheels and various parts to arrive for the tracks, I've tackled the boom drive problem.

At least for now anyway it feels much stronger.

[1gor]

Usually double acutators are much stronger than one, so this is defrnetly improovement

[cloud]

35 minutes ago, I_Igor said:

Usually double acutators are much stronger than one, so this is defrnetly improovement

I had two actuators before, but was driving both from one side without splitting the power. Now it splits in the middle and is more reliable.

[ginger-snapped]

I love the linear actuator idea. I might have to try that in one of my MOCs. Also, I think the first option for the front sprocket would blend in the best with your creation. Looking forward to more progress! Good luck.

[offroadcreations]

I think you should use either of the tires on the left or right for sprockets, but not the middle one. Keep up the good work on this, I'm excited to see it complete.

[BusterHaus]

@Zero (Zblj) used linear actuators in a very similar way, and the result was not pretty. The plastic piece on the end of the metal rod became disconnected. Ymmv. 

[cloud]

9 hours ago, BusterHaus said:

@Zero (Zblj) used linear actuators in a very similar way, and the result was not pretty. The plastic piece on the end of the metal rod became disconnected. Ymmv. 

That could be. The torque is not normally applied to them this way. On a previous version on my A40F I had them joined on the rod ends in the middle and free spinning on the drive end achieving the same extension result, but ultimately that has the same problem because of the need to have one end free to spin.

I would love to see any problems with this type of setup. Do you know roughly what topic this was under so I can narrow my search?

 

On an update note, http://cloudslego.blogspot.ca/2017/07/ec750e-boom-drive-part-2.html has another iteration of the LA drive gear sets as the one from yesterday was too wide.

Looks like this now:

15 hours ago, LvdH said:

One thing I am afraid of with that (genius) way of extending the LAs, is that under load the turntables and the 12T gears might skip gears.

I haven't had this problem with the new design as long as the small gears are well braced on either side and unable to pull away from each other the split sides with drive in the middle has worked.

A final play test carrying a full bucket load at full extension will show any remaining faults.

[BusterHaus]

@cloud Here you go:

 

[steph77]

Hi

looking at your build it seems to me that you don't have solved the major issue of this actuator setup.

Actually the whole wheight of the boom apply a pression on the axle who make your mini turntable rotate.(at the level of the technic frame, the axle with the tan 20T gear and the connection with 12T gear on turntable).

In my opinion there are no chance for this to work proprely due to friction, or you will encouter phenomenal losses of power at this point.

I do not know the solution but it seems to me that the axle of articulation of the turntable and the axle of the rotation imput have to be two différents one.

Even if it was,  it will remain the issue of the friction at the level of the turntable. You still will loose lot of power at this point. Normaly you would have to inject the maximum power with minimal friction directly at the point where your mechanism of lifting has to take effect. In your case all the power do pass through 'hard points' in the structure that are stressed under wheight.

At this point and even if this is a great  setup idea i think that custon made actuator based on cables or worm gear would give way better results.

I hope this can help you.

Keep it up!

Steph.

 

Ps sorry for my English level, i hope it still understandable for you :)

Edited July 13, 2017 by steph77

[cloud]

7 hours ago, steph77 said:

Hi

looking at your build it seems to me that you don't have solved the major issue of this actuator setup.

Actually the whole wheight of the boom apply a pression on the axle who make your mini turntable rotate.(at the level of the technic frame, the axle with the tan 20T gear and the connection with 12T gear on turntable).

In my opinion there are no chance for this to work proprely due to friction, or you will encouter phenomenal losses of power at this point.

I do not know the solution but it seems to me that the axle of articulation of the turntable and the axle of the rotation imput have to be two différents one.

Even if it was,  it will remain the issue of the friction at the level of the turntable. You still will loose lot of power at this point. Normaly you would have to inject the maximum power with minimal friction directly at the point where your mechanism of lifting has to take effect. In your case all the power do pass through 'hard points' in the structure that are stressed under wheight.

At this point and even if this is a great  setup idea i think that custon made actuator based on cables or worm gear would give way better results.

I hope this can help you.

Keep it up!

Steph.

 

Ps sorry for my English level, i hope it still understandable for you :)

 

Thanks for the comments Steph. The turntable spins with the XL motor and the boom plus arm stretched out all the way, but it does require a higher gear ratio. I'm hoping to carry a full bucket of small bricks and that will add a lot of weight. I will try a full load test soon to be sure it behaves as desired with the XL motor.

 

10 hours ago, BusterHaus said:

@cloud Here you go:

 

 

Oh dear. That is exactly the setup I have isn't it. Hmmm I must have gotten lucky to not have the rams spin the plastic bit around the end. Is it possible that the newer LAs have better internals for this connection? When the paired LAs reach their limit the internal limit clicks are heard just like the Volvo loader when it reaches its limits. There is also a small difference from that diagram and how I have them setup and that is that the plastic end is entirely locked in the direction perpendicular to the turntable which hopefully keeps any wobbling to a reasonable minimum.

I had rebuilt the gear set for the boom cylinders yet again and just got it to fit:

 

 

I'll reconsider the LA drive system. Maybe I can get the double length LA in some other way while still using LAs. Maybe driving them from both sides using the stock brackets like on the Volvo loader. That at least would remove the turntable friction.

I still can't imagine that the LA wasn't designed to handle rotation of the head since the head rotates when run without being connected. TLG must have considered this since the new ones have an internal clutch that I don't think can be defeated, but I'll be cautious and run my own tests first. If I destroy an LA it is better than all 8.

 

[cloud]

Recently it feels like a bit of stagnation on my part while thinking about several problems with the model.

I put several pounds of weight on the front of my BWE's arm to stress the LAs and they held up fine so I'll continue to move forward with my doubled LA design cautiously and do another weight test with the real thing later.

The problem with the turntable being too small is currently being solved by using a second turntable stacked under the first to pull up on the X frame as well as a brick-built "washer" like ring to spread the weight out more. Something like this is what I have in mind:

The turntable ends up being a hybrid of system and technic bricks/beams to spread the weight out and hopefully help with the model's presentation to look more realistic. What do you all think?

I just noticed that in the image above the center 11L beam is horizontal. It should be vertical.

 

Another problem to tackle is that I want to implement a 2 speed system in the shoes just like the real thing. I think I will do this with a CVT as it would be nice to have a smooth power out. The problem here is that existing designs loose all power when the output shaft rotation is stalled because they function on internal gear friction. I'm making a version with one way gears on the ratio side. I'll let you all know if it works or not.

Edited July 20, 2017 by cloud

[cloud]

Here I discuss my take on implementing a Lego CVT

It boils down to this in each shoe:

Dark azure is motor in, light azure is output. Green gears are low gear(1:30), yellow gears are "high" gear(1:4).

[1gor]

So far it is not possible to make proper LEGO CVT for Industrial purposes based on available parts...If you do not believe me, please first look at videos of CVT principle and how does CVT works on www.fendt.com. I know what is disappointment when you realize tjat CVT is not functioning in LEGO world  
 

[Jeroen Ottens]

56 minutes ago, cloud said:

Here I discuss my take on implementing a Lego CVT

It boils down to this in each shoe:

Dark azure is motor in, light azure is output. Green gears are low gear(1:30), yellow gears are "high" gear(1:4).

That is some out-of-the-box CVT solution. Do you have a video of it? The use of womgears is a stroke of genius

[BrickbyBrickTechnic]

15 minutes ago, Jeroen Ottens said:

That is some out-of-the-box CVT solution. Do you have a video of it? The use of womgears is a stroke of genius

I would love a video of the CVT! Very innovative.

[cloud]

13 minutes ago, Jeroen Ottens said:

That is some out-of-the-box CVT solution. Do you have a video of it? The use of womgears is a stroke of genius

Thanks, it is simply an analysis of the problem and it happens that Lego does have a solution.

This will be by basis for the shoes. I may still add a friction gear to the low range gear set in case the two L motors don't have enough torque to drive the full weight on flat once it is all together. The friction gear will only bias the gearbox to high gear by default and be overpowered once a real driving friction is encountered.

[cloud]

55 minutes ago, I_Igor said:

So far it is not possible to make proper LEGO CVT for Industrial purposes based on available parts...If you do not believe me, please first look at videos of CVT principle and how does CVT works on www.fendt.com. I know what is disappointment when you realize tjat CVT is not functioning in LEGO world  
 

I see you have reservations about this working, but could you please explain the problem with my CVT design.

In the link I posted to my blog I discuss the problems with the design commonly attributed to nico71 and propose a solution. I have built many of these to test out the idea so I am quite confident that it works. I just haven't built a good structure for it yet so I have no video. I plan on posting one once I have a more complete bottom end for the excavator. 

[suffocation]

3 hours ago, cloud said:

Here I discuss my take on implementing a Lego CVT

 

This is terrific! I'm struggling to wrap my head around it so I'll have to build it; but it looks like it should work once you figure out how to properly brace all the parts.

[cloud]

2 hours ago, suffocation said:

 

This is terrific! I'm struggling to wrap my head around it so I'll have to build it; but it looks like it should work once you figure out how to properly brace all the parts.

The photo of the excavator shoe implementation is coloured the same as the example photo from the blog. I've included an excerpt for explanation. 

Power from the motor turns the 16 tooth gear that drives the pink differential that drives a grey shaft and a black shaft. The grey shaft drives the yellow gear set for roughly a 1:5 ratio. The black shaft drives the green gear set for a ratio of 1:13. The two gear sets recombine in the purple differential and outputs to the blue 16 tooth gears.The output power equals the motor's output power at all times though the speed varies within the given ratios. In practice the whole system has a problem with using the low gear side even if the motor could drive the high side exclusively because the low side is easier to drive. A simple solution to this is to add a small rotational resistance to the low ratio gearset(green) before it enters the purple differential. The resistance needs to be equal to the gear resistance of running the high side(yellow gears) so that the green side is not used unless it is truly needed because the motor can not drive the high side.

[Saberwing40k]

The CVT sounds like a good idea in theory, but I think in practice and in terms of realism you'd be better off using a definite 2 speed gearbox, as done by @Sariel in his Brickshelf gallery. Also, I think your gearbox is not actually a true CVT, but an implementation of an automatic gearbox. Again, it's a great theory, but I feel it adds needless complexity, and it ends up being more of complexity for the sake of complexity. But, if you really want 2 speeds, Sariel again has a much simpler automatic gearbox, or a much stronger remote operated one.

By the way, I'm not trying to be down, but I've built stuff like this, and it sometimes doesn't work the way you want. Also, not having these mechanisms interconnected could be a problem in a skid steer vehicle.

[1gor]

7 hours ago, cloud said:

I see you have reservations about this working, but could you please explain the problem with my CVT design.

In the link I posted to my blog I discuss the problems with the design commonly attributed to nico71 and propose a solution. I have built many of these to test out the idea so I am quite confident that it works. I just haven't built a good structure for it yet so I have no video. I plan on posting one once I have a more complete bottom end for the excavator. 

@Saberwing40k just explaned very simply and with good intentions.

CVT is like when you leave water when you wash your hands; there is no precize ratio on watetflow, just two extreme states fully open or fully close and there are no steps between.

Differential compensate difference in between rotation factor on shaft or axles; eyample why do we need differential on driven axles - to compensate different wheel speeds in corner because outer wheel travels longer way...so CVT is something completely different. I've spent lots of conversation with good friend of mine who is ing.at CLAAS (and LEGO enthusiast) but true CVT is not possible...

Sorry to dissapoint you, when you look on my (old) Brickshelf folder, you'll understand my dissapointment

 

Edited July 22, 2017 by I_Igor

[cloud]

I'm quoting Wikipedia here:

A continuously variable transmission (CVT) (also known as a single-speed transmission, stepless transmission, pulley transmission, or, in case of motorcycles, a twist-and-go) is an automatic transmission that can change seamlessly through a continuous range of effective gear ratios.

 

If we look at how various CVT implementations work (Toyota, motorcycles, Honda, industrial tractors) there is such a large difference in internal design that one transmission can not be compared to another except by generic definition of a CVT.

I have looked at every Lego CVT that I can find including the un-translated slavic ones. The problems that I found were partially addressed such as in Nico71's use of flywheels. The solution to power loss that I came up with completely solves the problem. The remaining problem of gear range selection depends on the speed and torque of the motors as well as the weight of the vehicle since it is a mechanical speed control. 

I fully accept the burden of proof on me. I will make a video to show it working. Unfortunately it won't happen soon because I'm gone for most of August and September is always busy with the new school season. 

[1gor]

24 minutes ago, cloud said:

I'm quoting Wikipedia here:

A continuously variable transmission (CVT) (also known as a single-speed transmission, stepless transmission, pulley transmission, or, in case of motorcycles, a twist-and-go) is an automatic transmission that can change seamlessly through a continuous range of effective gear ratios.

 

If we look at how various CVT implementations work (Toyota, motorcycles, Honda, industrial tractors) there is such a large difference in internal design that one transmission can not be compared to another except by generic definition of a CVT.

I have looked at every Lego CVT that I can find including the un-translated slavic ones. The problems that I found were partially addressed such as in Nico71's use of flywheels. The solution to power loss that I came up with completely solves the problem. The remaining problem of gear range selection depends on the speed and torque of the motors as well as the weight of the vehicle since it is a mechanical speed control. 

I fully accept the burden of proof on me. I will make a video to show it working. Unfortunately it won't happen soon because I'm gone for most of August and September is always busy with the new school season. 

I agree partially but you have to realize that machinery uses hydrostatic cvt, with one hydraulic pump and one hydromotor. As a professor I give you one homework - study how hydrostatic cvt works