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

[jotta93]

I hope you can solve this problem, this is a very interesting build and one I'm very much looking forward to seeing the full MOC 

[1gor]

Do not worry, perfect moc takes a lot of time...it is something that you can not force and do not pay attention to time otherwise you will end up in frustration. Just take time that is necessary.

[Rudivdk]

I always end up rebuilding any moc several times from scratch, just to make it cleaner and implement all kinds of improvements. That's why I switched to digital building, much easier to change stuff and in the end only one rebuild is needed. But nothing beats building it with bricks, for the exact reason you encountered...

[MangaNOID]

Thank you for the input @Rudivdk @I_Igor @jotta93 all comments help a lot (whether praise or criticism )

 

The re build has been going well, although I have only been concentrating on the upper body not the undercarriage.

The battery box will be directly under the driver seat. All controls are in quite accurate position of the real one. scale is about 1:6 so I'll have to get some cheap 12" action figure to sit on here for the next update maybe 

 

I had to move the turntable forward in the model 2 studs (unfortunately for scale purposes) as that helped reduce lean when the arm was in the extended position. The mini excavators do not have much rear body on them that is behind the turntable to help balance the weight unlike other cranes or excavators. 

This caused all sorts of headaches with the track gearbox and coaxial positioning for me. There was not much room left upfront  but after a LOT of thinking I jumped on LDD and mocked up the chassis and found an answer fairly quickly. the end result looks simple of course but that's usually the case no doubt. I haven't tested the tracks under power yet though  but the sticks feel great. actually all the controls feel like they will be very intuitive (if they actually work!)

 

Structurally I am very pleased so far. It is quite rigid and the extended arm puts virtually no flex through the chassis.

left right arm movement is a few degrees off from the real one each way but I'll live with that.

I also managed to move the left right controls of each stick inboard which looks WAY better than having them outside. I am struggling with the aesthetics side of things but hopefully this will help me out with more external space. I do not think there will be many if any panels used on this model though and may try keeping it more open in looks.

 

 

 

the rear shot shows hopefully enough room to have a motor, double small pump and some gears etc.I am still hoping to activate the variable tracks from in the cabin somehow but that dream is fading.

Another problem which I haven't really tackled yet is where to put all these hoses! I have been keeping it in mind but I may get a 'oh crap' moment when I try and actually hook them up.

weight of the model so far with full battery pack is 1080g

 

[jotta93]

Looks very interesting! I can't offer much help other than suggest that you use flex-axles and hoses to build the body rather than panels, build it old-style  I'm really impressed with what you have achieved, way better and more complex than anything I could have ever done!

[MangaNOID]

I was thinking old-style @jotta93 but to me that’s studded stuff 

anyway I lost a little mojo on this so I’ll leave it for  a while and go on holiday for a couple weeks, but here is a shot of scale with a 12” male model to show its all fitting nicely.

the roofline is definitely borrowed from 42054 (with a Volvo sticker) but I hope I have captured the dorky look of these machines. 

Hopefully over the Christmas period I will get some motivation to shove a motor and some pumps in to see if it all works mechanically.

 

 

[1gor]

Shape looks OK, but you will probably make it sturdier in final version, so it could Christmas present for you (from yourself) 

[MangaNOID]

Thanks @I_Igor but looking at it today it seems a little off in the direction the aesthetics are going. 

I seem to struggle combining the 3 main elements of building a good model but ok at having 2 elements. We shall see what happens but I’ll have a building break on short holiday and then finish the functions before further tackling the aesthetics again which I seem to find the hardest part to do.

[1gor]

I know the feeling...that is why I use "blueprint" to check every height, width...angles are sometimes impossible 

I have decided to use ordinary steering in my latest project because under compressed suspension wheels are turning, an not to mention the slack...

Regards

[MangaNOID]

I had a bit of a break from this and went on a nice holiday to Tasmania but now back with not too much time to spend on it yet but I did play around with getting the motor in and hooking up some power to the drive and slewing systems.

a lot of problems trying to get the right speed to both as simply as possible without using too much space as there isn't much of that left.Also the two axles for the drive and slewing are only 2-3 studs away from each other. I tried using a worm gear but that did not work out at all with the drive system.

There is really no reduction in the drive system until the last cog set near the tracks either and the slewing needed to be really slow of course compared to the drive. the drive is a bit 'sticky' at the moment but hopefully that will sort itself out when I do a final build and keep all tolerances for free cog movement.

(slewing cog missing in below photo)

 

another thing I spent some hours on was thinking of a way to get power from the cab to the lower chassis to power a pump for the track width variation and the linear actuators for the front plowing blade/stabilizer thing. 

In the photo below you can see that I placed a few gears hanging down below with a clutch/gear set.

The idea being that the LBG 16T gear next to the red clutch gear spins freely until one of the red 16T are selected. this LBG 16T would then drive another gear set built in to the lower chassis (when directly facing forwards or backwards) and then drive the linear actuators (forward facing) but would power the pneumatic pump down below for the tracks (backwards facing cab)

Now this was all good and I was plenty happy with myself until I realised that the upper LBG cog when sitting on top of the lower chassis cog will be just that, sitting on top of it and not held to it in anyway! 

so I think that powering the lower chassis functions from the upper chassis/cab is finished unless I can come up with a way to quickly pin the upper and lower parts of the excavator together when wanting to use/demonstrate those functions. Is that worth it?

 

 

Also started fleshing out a bit of body work. nothing new or cutting edge here, and I will not be covering the whole body up, but just a few edges smoothed out for pleasant visual benefits and to provide a bit of defined shape

 

 

[MangaNOID]

I am getting a little bit confident that I can get all this to work. 

I have rearranged the drive gears/motor (several times) and think I have a winner now. Although I will not be able to use the standard Technic Battery box as its too big to fit in the desired space. but I think its OK as the smaller lighter box should still provide enough balance for the arm after putting in more of the rear cogs gearbox motor etc its getting heavy. slewing is nicely slow and drive is a good speed and managed to keep it quite compact. not sure of ratios.

 

 

the drive to the undercarriage for the stabilizing blade and hopefully the pump drive for the variable tracks width is put in place and will hopefully work well. Although the excavator has to line up directly forwards or directly backwards depending on which function you want.

the small pneumatic cylinder (below pic) will pull the axle down into the blue clutch gear. the clutch gear can then be driven in either direction with another switch/clutch lever setup, when this axle is in place which will then turn the axle.

 

 

at the bottom of that axle there is a Tri point axle thingy that will connect to the undercarriage gear drive (below pic) when that pneumatic cylinder drops. then a perpendicular axle goes through the undercarriage chassis to the front to operate a small LA for the blade up or down (that bit not made yet) I still have to get the drive to that system yet though which is where the DBG and red placeholder cogs are at the moment (below pic) as I am waiting for the right parts to get here next week to hopefully finalise it.

Also (hopefully) at the front, but just behind the blade will be the pump for the lower carriage pneumatics that will be driven by the same system when the excavator faces backwards. So I mean that there will be another  version of the Tri thingy below (with the blue axle pins) at the front, connected to that pump for the Tri thingy to drop into.

 

 

 

there is seven controls on the upper carriage. Not in a totally realistic positioning for some of them but is the best I could do and should be great for play-ability. If all goes well there will also be one more pneumatic switch in the undercarriage that will have to be manually switched for the tracks in or out function.

 

 

how its looking overall below...messy

obviously lots of bracing to do on the lever and lots else to do.

 

 

[jotta93]

I am seriously and eagerly looking forward to see the end of this! It's way too complicated for me to get how all of it works (despite the great description). If it all works and hopefully it will, this will be one heck of a MOC, one of the very best I have seen! Keep it up 

[MangaNOID]

big call @jotta93! thanks for adding that pressure  not sure it will be that good, but love your support   I find myself thinking of you as I build 

but I am getting a little excited each time a problem is solved.

Anyway, cant make a post without a photo, so here is some bodywork attempt seeing as I am getting closer to have the upper carriage functions finished. Love working in LDD in conjunction with the real build. It helps so much.

 

 

[BrickbyBrickTechnic]

This is a super nitty gritty build with some ingenious mechanisms. Well done and I can't wait to see the end result!

[kieran]

Very impressive pneumatic functions look really well done 

[MangaNOID]

I won’t hide my disappointment. This has turned to a fail. 

There are a couple clicking gears for the tracks in the upper chassis part where the  stick selecters are. I cannot fix this no matter how I try. 

if I had the MOC on a stand as a ‘show’ MOC then it would be ok, on the ground though it’s not happy turning. It is ok straight - forward or backward tracks going the same way, but I cannot live with the gear clicking.

its a real shame for me as I worked on the aesthetics and came up with a compact design I was very happy with.

This even had the 4x5x8 battery box squeezed in as the seat base.

so my next plan might be to ditch the single motor idea and have 3 m motors. 1 for each track and a third for the pump and slewing etc. I can possible put the 2 drive motors where the gear selecters were and have 2 PF switches right under each track stick. 

its not brilliantly technic but it’s a way I might be able to get this to function and keep the looks that I’m happy with.

and uh yea, maybe I need to build more official sets...

[pleegwat]

I've had similar experiences motorizing tracks with my BWE mod. Moving both tracks in the same direction would work fine, but moving one and keeping one stopped was iffy at best, and running both in opposite directions was a no-go. However, since I had separate motors on sbricks, I could also do things like run one motor at 50% and the other at 100% which worked excellently

[Lipko]

So it's not a failure, you just have to change some concepts. That's perfectly normal design process (at least for me)

[MangaNOID]

Your right it’s not a total failure I should have just checked the gearbox a long time ago! Still trying to figure out why, where exactly it’s clicking.

Also I’ve been fiddling about in LDD and have managed to fit the m motors and switches almost exactly where the gears were. I have ordered two switches to hopefully come next week.

if this works it will leave a little more room in the back... for something...or just a little more room.

so I’ll probably not post on this again until it’s finished as it’s been dragging on for anyone following for almost 6 months now So hope I can get it right.

[jotta93]

On 2/12/2019 at 5:15 AM, Lipko said:

So it's not a failure, you just have to change some concepts. That's perfectly normal design process (at least for me)

Exactly! It's part of the building process. It happens to me countless times.

And it has not been a bummer to follow this, quite the opposite 

I will eagerly await for the final MOC!

[MangaNOID]

On 2/13/2019 at 8:55 PM, MangaNOID said:

so I’ll probably not post on this again until it’s finished as it’s been dragging on for anyone following for almost 6 months now 

Sorry, im posting an update as it keeps me motivated.

the transplant of the m motors and polarity switches has been quite successful. Although they are very visible in the current position. 

 

I had to move them from being directly under the tracks  levers as the throw on them is too much with the long levers, so I put them off to the side with a liftarm setup connector to decrease the throw by about half.

reverse sticks...

Forward sticks...

 

The tracks drive really well now. No clicking through the coaxial etc. I hAve a worm gear setup with 8T for final drive to each track though.

I connected the arm pneumatics and all is working well! I am hoping one small pump feeding an air tank will be enough for continuous ‘play’.

[1gor]

Now this is what I call improvement 

Very good idea how you operate polarity switch.

Finally project is on rolling again and this time I think in good direction.

[Phleep]

Desperately want to recreate the finished article when it's ready. Thank you for sharing the process.

[MangaNOID]

7 hours ago, I_Igor said:

Now this is what I call improvement 

Very good idea how you operate polarity switch.

Finally project is on rolling again and this time I think in good direction.

Thanks! I hope this is on track too! This feels better solution when using the tracks for sure, really solid feeling and can stall the motors without clicking if I put my hand in its way, but still a little disappointed with this solutions lack of Technic’ness.

4 hours ago, Phleep said:

Desperately want to recreate the finished article when it's ready. Thank you for sharing the process.

Thanks! I’m building an LDD file as I build and would like to make instructions for this even if it’s just for me to re build one day (if it all works in the end that is) but I realise how difficult instructions are and what with pneumatic tubes going everywhere it could be well beyond my abilities. We shall see.

 

And I can’t post without a picture so here is how the tracks sticks work to the polarity switch. Its not a solidly connected connection but it works a treat. Although the feel of the switches is not as nice as the gears and clutch parts from before that click in place.

 

Also (because we all like pictures but with fear of over saturation) there will be a couple of built versions of this (in the digital world anyway) one version will be built with the Lego rechargeable battery box as the seat base and the pneumatic tank outside the body behind the driver seat.

 

The build I will do in real bricks will have ‘loose’ single 9V or Li-po battery under the seat with the pneumatic air tank hidden under the seat also to keep the outside look a little cleaner. Each version is easily changeable to the other with no real chassis modifications needing to be made.

 

 

[MangaNOID]

small but significant update is that I have finally sorted out the pneumatic setup for the upper chassis. This proved very frustrating to me.

I have settled with 2x 6L pumps driven by one XL motor, which also drives the slewing and lower chassis stuff like dozer blade and tracks expansion (if they work as I haven't made that circuit yet)

one pump drives the main boom the other pump drives all other pneumatic functions. I started off with an M motor for all of this but when pressure built up in the lines when the pneumatics were not being used the motor slowed and stalled untill the pressure released by using the functions. that meant no slewing could be done either so I had to go back to the XL motor, but that was a lot slower than the M motor in RPM so I used a chain drive to speed the pumps up a little. 

It works quite well but all a bit in slow motion. maybe that's normal for Lego pneumatics though. I tried double pumps on the one circuit but I just could not make that work under load 

I have done away with the air-tank too as that hinders rather than helps in this setup for some reason. I guess the small pump takes a long time to fill the tank, to then send that pressure to the cylinders rather than straight to the cylinders.

 

 

 

I re worked the rear section many times to get this setup below that seems rigid with the chassis and good enough for splitting one motor into high speed pumping and very low speed (~5rpm) slewing

 

 

without the air-tank I should also be able to put the battery box 8x4x5 (even though I wont be using it I did want to make it pure Lego build in theory.

big relief to get this part sorted so i can work on the undercarriage blade and single pump now.

the controls are very nice to use, very intuitive, just like the real compact excavators!