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

[MangaNOID]

hey all

thought I would start a WIP of my new project which is a generic Mini Excavator. Although it is loosely scaled on a TYM TE1800.

what started this is the Calypso helicopter I built. I was a bit disappointed to have not used any swashplate technic awesomeness that @steph77 was so helpful to help me understand. so I have taken the swashplate operation part and decided to use these as the controls of the excavator. In the correct place (cabin) and set up like a real Mini excavator iso controls (as best as I can of course)

• Left hand left = cabin slew.
• Left hand right = cabin slew.
• left hand forward = Stick Boom (Dipper) away.
• Left hand back = Stick Boom (Dipper) close.
• Right hand left = Bucket curl in (closed)
• Right hand right = Bucket curl out (dump)
• Right hand forward = Main Boom down.
• Right hand back = Main Boom up

the idea for these swashplate controls is hopefully to have a bit more control over the pneumatic movements with the new axle hole switch. the switch will effectively be geared down or the movement halved so at maximum operator stick angle there should only be half the pneumatic switch angle operation. So hopefully slower, finer control of the cylinders...we will see.

now it all looks pretty untidy at the moment with lots of extra bits sticking out for support whilst I work on placing all the functioning parts.

it is going to be pretty compact in there if i can get it right at this scale. I have had a lot of headaches already just getting to this stage.

tracks are not to scale and will not be the ones used. they are just holding everything up at the moment.

 

this is the slewing which is connected to the gear clutch

 

the pneumatic switch will be connected to the black axle sticking out. The axle will be solidly connected to the 7L beam when finished instead of the 1L bush 

 

this will hopefully be the track controls. space is real tight so i am trying to control the gear clutch with the 3L bar. it does work but the lever arm has to be 'held' in place with the cabin floor to stop it popping out of the clutch.

 

very long way to go!

 

 

 

 

 

 

Edited September 19, 2019 by MangaNOID

[1gor]

It looks interesting, but i would Rather use new treads and sprocket wheels. I'll peek from time to time to see how your project develop 

[mpj]

Yes it is interesting for me too, even if at the moment I can't understand how it will work, so I'm looking forward to see the progress 

[nerdsforprez]

29 minutes ago, I_Igor said:

It looks interesting, but i would Rather use new treads and sprocket wheels. I'll peek from time to time to see how your project develop 

Again, helpful to read entire post.  OP already mentioned he will not be using tracks shown 

[1gor]

21 hours ago, nerdsforprez said:

Again, helpful to read entire post.  OP already mentioned he will not be using tracks shown 

I understand but I have just wrote what I would do...

[MangaNOID]

So I have had to almost start again. The first version left no room for the coaxial drive from the cabin so version 2...

I started with the coaxial drive and then implemented the slewing as that took up a lot of room. It’s much better now, less room. All on one side direct under the controls with drive coming from the rear where the motor will be. Here is a short vid of it operating (slewing speed is too high but it is just a demo.

I’ll have to get some new pneumatic switches now but they should fit in nicely where I left room and operate off the forward and backward stick position (on this left side control)

im not sure what the scale will be but I am trying to stick to 17 studs wide for the body.

tracks are roughly to scale of final.

hopefly I can add to the chassis easily and strengthen.

plan is for 1 motor to power everything, pneumatic pump, 3cyl engine etc. hope there is space.

[1gor]

Now it looks promising, what I like is a "framework", well probably because I use frames 5 X 7 and 5 X 11 as much as I can, they are relatively light and construction is very stiff. Usually this kind of machine use 6 cylinder engines, sometimes 4 but I could be outdated, so you will know what is best solution for your MOC 

[MangaNOID]

Yes I now have a whole bunch of black frames so I will use those as much as possible too.

Pretty sure this is 3cyl with .993 displacement. 

And just read this TYM 1800 has expanding tracks width! Not sure I’ll be able to implement that especially controlled from the cabin but I’ll keep it in mind now...even though this is a generic excavator I’m up for a full challenge...then scale back to what reality can handle 

 

[1gor]

I'll keep my fingers crossed 

[steph77]

You CAN do it

Just build the second controler and go :)

 

You have build a perfect proof of concept actually, the hardest par is done.

Looking at your model i Wonder if it wouln't be better keep the gearbox behind the controler not one up the other to maintain a good scale proportion.

And by the way this configuration is perfectly adapted to....linear actuators

And at last, you need to fix quickly the position of the battery box

Keep this up!

Edited September 4, 2018 by steph77

[MangaNOID]

thanks for you encouragement Steph77 although I am not sure the hardest part is done...

 

I decided to work on the under carriage for a bit and try and work on expanding tracks. what a pain in the bum.

to take the load of the excavator (about 1-1.2 kg tops) I decided to use pneumatic cylinders (after trying a whole bunch of stuff) as they had less flex than anything else I tried.  They also fit in to the scale that I wanted.

I built a fairly awesome solid chassis with coaxial drive to suit that is also fairly compact. took ages but I am happy with it and its dimensions which suit length and width/s of tracks.

now as this is supposed to be a pneumatic model then using these cylinders to expand the track also is obvious. except that I can not get them to open evenly. Even just on one side. some cylinders slide easier then others and they end up opening wonky and then become parallel when the end expansion point has been reached of course. maybe I'll have to live with this.

I thought about linear actuators to expand the tracks which would (possibly) work but there is not much room and they look a bit ugly.

a pneumatic tank hooked up helped a lot but is still not perfect and they open very quickly ruining the spectacle of the opening.

I also tried lift arm 'guides' through the chassis but there is still some wonkyness due to Lego gaps

desperate to try and keep the cylinders to do the opening so if anyone has any suggestions about even opening rates it would be great full. I've tried quite a few things but I am lost.

 

 

 

 

 

 

 

[Seasider]

the problem with pneumatics (even in the real world) is they often don't work smoothly especially if you have multiple pistons pushing at different points to extend something.

remember they're all about pressure and friction

i know you said you dont want to use them but linear actuators would be better or how about using some gear racks ?

[MangaNOID]

Gear racks just won’t fit. Well they would, but they would be well visible and messy looking and unsymmetrical etc as far as my thoughts go anyway.  I’m really trying to have a neat looking MOC as well as a technical one this time. 

Small LA’s are a similar problem but I may have to live with them and try hide them where the pneumatics are now and move the pneumatics out (to hide the LA’s)

 

the thing is I can’t see any other way of connecting the tracks to the chassis without the use of pneumatics cylinders as the cylinders slide, and hold the weight of the model. Small LAs don’t do that.

another thing is that i really wanted the control of this to be in the cabin, which could make gear connection and LAs better...I may have to re think my plans a little and compromise  I have one last idea to try when I have time to get the pneumatics working, then rebuild time if it’s a no go.

[MangaNOID]

Needs some tidying up but it works with pneumatics and feels pretty solid.

will finish it off when back from holidays in a couple weeks. 

Very happy so I’ll leave it on a good note for now.

 

 

[MangaNOID]

so I'm quite happy with this outcome of finishing the variable track width pneumatically even though my grey matter is absolutely fried because of it.

these are the first tracks I have built and I got to say it was difficult  (The video in the previous post above just had placeholder tracks for dramatisation) even though this is supposed to be a generic mini excavator I ended up trying to build to the right scale of the TYM1800 and in the end it paid off with the length, height, ground clearance and both widths being pretty much spot on. Although maybe 20 hours! was spent making the tracks (not including the chassis that is)

the pneumatic hoses have yet to be put in properly so they are just hanging out at the moment. Hopefully the plan is to have the pneumatic switch manually operated in the lower chassis with the small 6L pump in the lower chassis too but somehow operated from the cabin with a drop down gear or something when the cabin is in the right (forward facing straight on) position...we'll see how that one goes.

there is some colour discrepancies which will be fixed on the final version.

this is what the real machine looks like by the way that this is loosely based on.

 

my tracks...yeah I'm not sure about the red knob either.

 

 

 

scale is pretty good with rear of the tracks 1 stud longer than the front like the real one is slightly offset

and the two widths line up nice with 2 studs variation of track width for each side so 19 studs width in and 23 studs width out.

 

 

The Technic bricks you can see in DBG with the LBG tile on top are the guides to keep the tracks as parallel as possible when they move out. they work quite well held in place by the 'T' pieces.

 

 

The blue half lift arms etc below are the 'stops' for the pneumatics as I had to only have 2 studs of travel but of course the pneumatics have 5 studs or so of travel. also the drive shafts cant handle anymore than 2 studs of lateral movement.

 

 

 

Here is a vid of them being operated and also showing how fairly structurally sound they are with 1kg of weight put on top which is more than what will be on top from my calculations of one Li-PO battery box, one XL motor etc etc.

you'll notice that one tracks side comes out before the other and not coming out together, but that is how the real ones work too from all the videos I have seen so I am OK with that.

 

 

Edited September 30, 2018 by MangaNOID

[MangaNOID]

first up sorry for the colour vomit. it doesn't seem to photograph well for showing things but it is easier to build without thinking of colour schemes until the model is finished of course.

 

Unfortunately when I tried the new pneumatic switches in the controls it didn't really work so well. there is a lot of force needed to turn the axle hole. I tried increasing the leverage as in the photo below which has 7L leverage but that then limited the movement of the switches to very little, very slow cylinder movement. please not that this is a quick mock up for the photo as I had taken it apart in disappointment before I thought of taking a photo. but it should show the gist of movement to the switch from the stick, swashplate then through the horizontal 7L?

 

 

so this is what I have now, which is ...OK. the only drawback is that it is swinging the hoses when the switch moves left/right. Hopefully that will be ok. I think there are softer hoses from earlier sets like 8459 that I recently bought. hope it works or this project is cactus. Control over the forward backward of course is superb.

 

 

otherwise overall everything else seems to be going OK. i have the track controls somewhat sorted which are the two sticks comming up from the floor of course. the floor of the cabin should be (for accurate scale) the top of the black  technic bricks between the sticks but i may need to add one plate height on top like the 1x8 system bit there to cover everything nicely.

the right control stick (on the left of the photo) controls another pneumatic switch lower down for the left right action.

 

 

I had to lift the pivot point up for the track control but that helped reduce the arc movement of the top of the sticks which will hopefully be good for playability.

 

 

 

 

It sitting higher off the tracks than it will in the end as I just didn't want to mate the top and bottom together yet whilst still working things out.

 

[1gor]

It looks very interesting with this variety of colors like you own 42082 set. I like undercarriage 

[MangaNOID]

Indeed hideous colouring like 42082, Can't really bring myself to buy that one, and rather, I cannot afford official sets these days with young family etc, so I must bricklink all special bits that I need such as the 20T clutch gear above and the pneumatic switches. 

18 hours ago, I_Igor said:

 I like undercarriage 

Thanks! I am quite happy with this, although the other day when I was putting a lot of pressure through the model unknowingly they half 'popped out' as they are really only held on by 2 pins each side, on the ends of the pneumatic cylinders. It was a lot of force but I may need to revisit that. We shall see how the models weight and playability end up. plenty of room for fixing that if need be I hope.

 

[Jurss]

This becomes very interesting

[1gor]

Perhaps you could use linear actuators (they are more smooth when operating) instead of pneumatics on undercarriage (but fir this you would need additional axle to go to undercarriage...). You'll see what is the best. If you managed to make it work it would be better than original tracked loader / excavator...now when I see original I must admit that it is great MOC (despite still in development) 

[MangaNOID]

Have been working on the arm attachment and stiffening up the upper structure recently. I found it quite hard to add the arm and have it turn left and right as well and not bend the whole upper structure out of place with the weight of the arm at reach. I am using plates to hold eveything back to the center or rear part of the upper structure as there is not much room for anything else to be used. that is working well though and will help when adding some detail to the cabin area later.

 

 

But with the weight of the arm (arm is unfinished) on there now the problem of a twisting undercarriage is showing itself.

in the photo below you can see a slight slant downward left to right on the middle part of the undercarriage where the turntable sits. I think it is because the only real attachment points to the tracks are through the pneumatics which are roughly attached where the two yellow lines are. which means they are very central to the structure leaving a lot of slop when weight is put on any far points length ways to the chassis.

there is no triangulation stuff going on to stiffen things up that is.

I may be able to rebuild the chassis and widen the pneumatics, but only on the side where the plow, or stabalizing thingy (left of picture) is. there is really no room on the side where the drive goes to the tracks.

 

I may indeed have to completely rebuild the undercarriage and setup a different drive system. I don't want to give up the variable tracks just yet as it would be a great feature to retain.

[MangaNOID]

so I'm probably not going to win any award for accuracy with the digging arm motion, but this is not an exact scale model of course, and its not too far off?

If its clear in the photo, I highlighted in pink the motion of the original to compare where my bucket arm sits. A little bit more work to get it better but I'm quite happy. The arm will drop a little more as there is a technic brick to be relocated that hits the first cylinder stopping it from reaching full downward vertical which will get it more closer to the line.

I lined the overlay image with the body and pivot point of the arm and not the tracks of course.

 

 

 

 

 

 

the arm is 3L wide but having the hoses clamped on the side make it 5L which is too wide and impedes operator view, but I'm struggling a little to hide them any better so far.

also a little concerned about needing two battery boxes to balance it but i guess its not finished and there is the gap and two turntables to get rid of between the tracks and upper body.

[MangaNOID]

Disaster has struck my build with me not knowing the parts well enough.

after having the arm on the excavator the weight shift/slop through the whole chassis and body was so annoying that I could not continue. 

After close inspections of where the wobble or slop was coming from I realised the parts in LBG (photo below) that I have connected to the turntable (both top and bottom are connected like this) have less friction than standard friction pins making these parts slip/slop loosely. There appears friction lines only on one end of each pin.

So on to a major rebuild. 

 

 

[Rudivdk]

I found myself that adding a friction pin through the center holes of the crossblocks helps a lot (but in this case won't really help on the turntable itself....) Do you need the vertical pinholes for your build? Otherwise just replace them with beams and frictionpins. Or put just 1 crossblock with blue 3long frictionpin in the middle, in the three holes of the turntable?

[MangaNOID]

thanks @Rudivdk I did need those vertical pin holes as that is where the pneumatics in the undercarriage were attached too.. I thought I was being smart using the cross blocks. I may try your Idea of one crossblock in the middle for when I re build the undercarriage as that sounds like a good starting point and would still work with where the pneumatics attach, thanks!. At the moment I am starting with the upper body.  I am not too disappointed in a way, as I have learnt a lot and felt like the build was getting rather messy and make do in many areas so I will try to avoid that this time.

very much still enjoying this build despite setbacks.