[WIP] Pneumatic Mini Excavator - almost finished but on hold

[ben20]

Aewsome model and functions. The goal for a good compressor is high rpm and  two pumps for a good air flow in your model is more then enough. An air tank is only good when you need no contol over a cylinder, otherwise you have or no volume in the circuit or to much

[MangaNOID]

that make sense the way you say it for sure. In fact you gave me an idea of how I may be able to speed it up (just the pumps) a little more. I'll see if it helps any.

another thing i forgot to mention is that i had to take apart the cylinders to get them working smoothly. Even though they were not used much at all from 42053. I added some vaseline to the bore and seal which worked a treat. instead of taking 40-50 pumps of the small 1x6L pump it only needed 15-20  to extend a large cylinder. much more efficient.

[jotta93]

I'm glad you've solved the pneumatics.

I don't have much time for LEGO right now but I'm still following with care this and can't wait to see the final model in action 

[MangaNOID]

Thanks for the enthusiasm Jotta93! I hope you get some hobby time soon! I get about 5 hours a week at the moment. plus some thinking a doodling time at work of course 

 

So, I’m getting a bit hesitant about whether the expanding tracks (especially in this non manual form) is worth it or not. It is compromising the structural integrity of the undercarriage. Mostly when doing the ‘excavator trick’ below though, so I will continue, everything is working…Just!  but this certainly would not make an official set with this setup. I’ll hopefully explain as I update.

 

One of the main things I wanted this excavator to do is be able to lift itself off the ground, to then be able to expand its tracks. Just like the real ones can do. I do not think this is entirely necessary on a real one (or this one on a smooth surface) but is a neat trick.

 

I just finished with the front blade (almost. it needs a little cosmetic tidying). It is ‘upside down’ compared to most setups as the drive axle comes through the very bottom of the chassis from the rear, so had to put the LA’s at the bottom. But this blade is driven from the upper body and can, so far, lift the excavator.

 

 

After that you have to slew the upper body around 180 degrees (it only just manages to do this…just, because of the slope angle of the body) and use the digger arm to push into the ground to lift the whole thing up on only the bucket and the blade. Unfortunately the small pumps are nowhere near strong enough to do this on their own so I have to switch (pneumatic switch) the main arm cylinder over to a large manual hand pump to pull this trick off. There is still a little more weight to go on the model such as small battery, roof and operator seat but hopefully it will all still work then 

 

 

 

In this pic below you can hopefully and rather unfortunately, see the weight pressure on the turntable with the undercarriage quite angled compared to the upper body. only one side of the upper and lower parts take the weight which causes this squeeze 

 

 

 

So I also admit I have to get some threaded axles to keep the blade held in to the chassis at this stage as any wobble or sudden movement can, at the moment, pull the LA’s out and everything collapses. I have one from my 8851 set but need another on my next brick order.

 

[Kio Liex]

Really great work. It is impressive how realistic it is, with all the levers and functions.

Sorry for asking (I have not read all the posts), but are you planning on making instructions?

What about using the big LEGO Star Wars models as driver? I belive that they can be modified to look like a worker.

[1gor]

Perhaps you can copy turntable solution from Liebherr or make something similar to prevent squeezing...

[MangaNOID]

Hey @Kio Liex thanks for your comments! I hope the end results will be impressive...we shall see  good suggestion about the star wars figures and i wanted one for the model photo shoot in the last pages but I do not think i'll be adding a driver. maybe for some still photos but the extra weight may make this a failure 

Good suggestion @I_Igor and I actually do have a small 'brace' thing on the front and back of the turntable. it helps a little but I think in the above photo the flex might be exaggerated do to the flex in the blade support...hard to explain but I have re designed a new blade support that may be stronger (yet to build it) we shall see. no matter what though I will not eliminate the flexing. I did try another support much further back but the weight going through it pulled some of the upper chassis loose! I may just need some more of those threaded axles.

below is a look at the new blade setup. hard to see probably but anyway, the green axle is where the threaded axle will be. the pink thing floating is the drop down drive that mates to a turny thing below to drive the small blue pump for the track extenders. there is of course as mentioned another turny thing the other side of the lower chassis that drives the blade LA's up and down

 

 

 

 

 

Edited April 7, 2019 by MangaNOID

[MangaNOID]

6 steps forward 5 steps back so I haven't updated much as I'm just tweaking what I have really. I wont list all the tweaks there is too many.

highlights though so far are that I am less negative abut this build after realising that 5 of my 7 small 1x6 pumps don't work very well. i do not know why but i will try to clean them? they work an unloaded cylinder but will not work on this model which was obviously annoying until I realised this.

so now using the 2 good ones I have the model can indeed lift itself up  using  the main and secondary arm (and the blade of course). it takes a little time but none the less, it makes me happy.

this now still leaves room for a LEGO battery box which I am happy about indeed!

testing all the functions now seems positive so I am now doing open undercarriage surgery to place all the pneumatic hoses for the tracks expanding. it is VERY tight for space so I have to have no slop in the hoses and be as neat as I can. I only had some yellow leftovers to use as hose which looks awful but it shouldn't be seen in the end at least.

 

 

 

 

 

 

 

after testing this it really should (hopefully) be just a small bricklink order for some parts for the seat and other cosmetics and a couple more threaded axles.

 

[1gor]

I hope that you are right. Your work on pneumatic excavator gave me idea to make my Fastrac with pneumatic 3 point hitch. I can not complain on one thing - I would make it yellow.

Regards

[MangaNOID]

thanks @I_Igor seeing others builds sure does get your own ideas flowing. speaking of which I had some inspiration from this build below.

 

it was the only mini excavator that I found on the net and wanted to proportion mine similarly. which is also why mine will not be yellow of course. I rather like the red and white of the Japanese Takeuchi brand. anyway I hope that colour will be the only thing to procrastinate on with this model if it all comes together.

[1gor]

@MangaNOID I have a plan to make more JCB machinery in future and one of them is JCB Excavator, but for now I'm Concentrating on systems tractors and telehandlers...

Regards

[jotta93]

Looks really good! I'm glad you solved the pumps issue and hopefully you can minimize the flexing of the chassis. I cannot stress enough how excited I am for the end MOC 

[MangaNOID]

Hold your excitement @jotta93, that only leads to disappointment!

 

-This thing is getting heavy and almost too heavy for the two M motors to move it.

-The track expanding pump spins so slowly that it takes a whole minute for the tracks to expand or retract.

-There is gear slipping when slewing left.

-The drop down mechanism to drive the lower chassis functions has to be very aligned for it to drop into the lower chassis drive thingy’s. Slewing to those points is a bit frustrating.

-The blade moves faster going up than it does going down.

-The tracks are a little flexible as said before, as they are only secured on by two pneumatic cylinders each side.

-The drive wheel in each track rest on the ground (instead of usually lifted up a little) so the drive movement is very bumpy as the wheel ‘climbs’ over each track segment,

-maybe some other stuff...

I can fix maybe one or two of those things above but to fix all of them I do have to get rid of the expanding tracks. They are the trouble maker in this build. I will finish the model with them and post a video but after that I will no doubt build a model without the expanding tracks which will be way lighter, more playable, more structurally robust and just better all round I think. too much stuff going on maybe ruins a good model.

 

call me Mr Fickle with this build. 

[jotta93]

I'm sorry to disagree with you! Sure there may be some problems with this model, but that's the fun of LEGO. Nothing is ever really fixed, everything can be endlessly improved 

I'm hoping to se the finished MOC with the expand tracks. And I'm sure you'll be able to fix some of the issues you mentioned. And if you decide to take away the expanding tracks please do me one favor: at least make a video on how they work, take some good detailed photos of them and maybe one day you'll come back to this MOC and have an Eureka! moment. But, please, don't give up! I am seriously waiting for he end of this

And no disappointment for me, only genuine interest and admiration from someone who also loves LEGO and struggles (a lot, really) with his MOCs 

[jorgeopesi]

I learned a lot from Lego and one important thing was to give up before starting, it is not a MOC that you should not have started but it will teach you limits for the next ones, we are all on that learning path and the good thing about these mocs is that you can always approve ideas for others. Looking back there is more than one MOC of mine that I detest and before it seemed unbeatable. I admit that my Lego sense told me that this MOC was impossible but we can always wait the best, with more space you will do awesome things.

[MangaNOID]

14 hours ago, jorgeopesi said:

I learned a lot from Lego and one important thing was to give up before starting

Haha! If only we all had the willpower to do that. Your whole post is one of reverse psychology inspiration for sure I know this won’t be the best build but if it works without falling apart and has the functions I originally wanted (operated from the cabin) then I’ll call it a success. I am being positive today (after last night-see below) as the only flaw I see in it is the slight flex in the tracks in relation to the undercarriage chassis. I’ll make sure to show this in the video for anyone interested.

 

Once again @@jotta93, Thankyou for poking me in the ‘continue’ direction. There are so many times I have been disappointed and just wanted to do something more simple with this but I do find it hard to give up ideas (even if the end result is a little compromised) there will be a video on this for sure even if it does end up highlighting the inadequacies of this build

But, I did have a good 45minutes last night to test some thoughts and test the operations again and it was looking rather good after a couple changes! So I’m Mr happy today.

I didn’t think they would fit so I never put them on but after trying last night the little round wheel things for the tracks do indeed fit and make the drive much smoother! I can have 3 each side.

I also reverted to a previous setup (I’ll spare the boring details) that allowed the tracks expanding pump to be almost twice as fast. So much better.

So a couple items scrubbed off the list from above.

I’ll try not to overwhelm the airwaves here. I’ll wait for my bricklink order. Fix another two items from the above list, Shoot a video and come back with it all done soon I hope.

[Kio Liex]

Fantastic that you keep working on it. I have also experienced that some ideas seems impossible to implement, especially with my Volvo front loader, but after several redesigns and test it somehow turns out okay. My kids think that I am a little crasy rebuilding the same part/idears 10-20 times, they can't really see the small differences. At the moment I am struggling to get room for the motor and the shifting parts for a 4 speed gear box in my current MOC, a Volvo FH truck.

One thing I do that helps me is to put the project a side if it seems that I am not having any progress, then after some weeks I take a look at it again and then it seems a lot easier to continue.

Keep up the spirit.

[jorgeopesi]

30 minutes ago, Kio Liex said:

Fantastic that you keep working on it. I have also experienced that some ideas seems impossible to implement, especially with my Volvo front loader, but after several redesigns and test it somehow turns out okay. My kids think that I am a little crasy rebuilding the same part/idears 10-20 times, they can't really see the small differences. At the moment I am struggling to get room for the motor and the shifting parts for a 4 speed gear box in my current MOC, a Volvo FH truck.

One thing I do that helps me is to put the project a side if it seems that I am not having any progress, then after some weeks I take a look at it again and then it seems a lot easier to continue.

Keep up the spirit.

I do exactly the same.

[Arnoob]

I am a complete newby  in Lego Technic (haven't been playing with it for decades until my grandson urged me to buy and build the 42055 excavator) but I am absolutely stunned by this build! Not understanding half of what I see here I hope my understanding of your complexit MOC (what is the meaning of all abbrevs on this site ...?) even comes a little bit near yours.

[jotta93]

13 hours ago, jorgeopesi said:

I do exactly the same.

That makes two of us. But one thing I do not do is take apart a failed MOC so than I can always get back to it in the future if I have an epiphany.

@MangaNOID, You don't have to be thankefull, I meant every single word and I'm happy that you solved some of the issues 

[MangaNOID]

Thanks for the comments people. Sorry it’s been a while to post here (but I’m sure you carried on with your normal daily business whilst waiting ) I’ve been waiting for parts and building time!

More importantly I have changed how the tracks expand.

This is due to changing from 2 studs expanding to 3 studs expanding each side, so 17 studs wide to 23 19 studs wide to 25 studs wide. I did this because I could barely see 2 studs difference when they expanded and after measuring them 3 studs was more accurate in scale of 1:6 compared to the real ones so I had to fix that…at a cost…

 I have done away with the mechanism that dropped down from the cabin. Although it worked it didn’t work that well as said before you had to be right on top for it to drop down and connect to the undercarriage part. Also after going 3 studs expand the flimsy track connections made the whole excavator wobble around a lot. It would have been great if this model just sat on a stand as a show piece, but you know…

Below is the tracks at 3 studs and how flimsy the connection is. Remember the tracks are only held on by two pins either side at the extended side of the pneumatic cylinders. They take the weight of the model really well but anything off balance creates leaning issues.

 

 

So now I have two pins either side at the back of the tracks (the red ones in the above gif) that you pull out and push back in to make the tracks more rigid. A little fiddly but works well especially when the front blade is on the ground!

Also at the back now (below pic) is the pump for the tracks which is manual operation and under that is the now manual cog that controls the front blade up/down  

So not everything controlled from the cabin now which is a pity but compromises had to come.

Getting rid of that stuff has allowed me to get the XL motor buried deep in the body with the 2 main pumps low down also which now allows room for a 3 cylinder engine and some small engine bay details which perhaps makes the model more complete?

 

Edited May 31, 2019 by MangaNOID

[Mechbuilds]

XL TORQUE!! 

It's getting better and better. 

[jotta93]

It was tough call I bet! But if by making everything in the undercarriage manual you can now make a more detailed model, I'd say it was a good choice 

[MangaNOID]

it was a tough call especially after its been about 7 months of very slow building time! (anyone still following is bored of these updates no doubt ) I still think this will end up better overall though with it being closer to a scale model (with the extra width of the tracks and engine)

really not much to go now. I have an engine bay with chain driven engine and the radiator 'fan' should turn when everything is operating

 

last big thing though is to see if I can make  better boom arms as its looking a little...rough/un-neat. I want to try getting the main boom cylinder on top of the boom arm instead of the usual underneath, as some of these compact excavators have that setup.

[MangaNOID]

this project is on hold for a short time for another project (Lego) 

A few things to finish cosmetically (seats) and it works as it sits but still not great with the tracks widening so also thinking about going back to original setup with all controls in the cabin and just mounting the whole excavator on a small stand (so the track still touch the ground) and have it as a working display if that makes sense.

as she sits right now with tracks in wide position.