Excavator side project

[Mcgyver]

Nice work Chris.  What did you do for drawings, or reference from which to create drawings?  To me that is one the great challenges with these projects.....I always wondered how the plastic model companies manage to fairly accurately it seems model so many and different items.   I also thought they might be a good to source to reverse engineer from

[crueby]

Nice work Chris.  What did you do for drawings, or reference from which to create drawings?  To me that is one the great challenges with these projects.....I always wondered how the plastic model companies manage to fairly accurately it seems model so many and different items.   I also thought they might be a good to source to reverse engineer from

I went just from the diecast model that I found, is in the pictures under the boom. I put it across the room and took pictures from top/side/ends with the camera on telephoto range, then used those as a background canvas in Fusion 3D and traced around the shapes to get the curved sections. Some of the parts were also measured with a caliper and scaled from.  Not a millimeter-level of accuracy by any means, but good enough for a stand-off scale working model that will be used to play in a dirt pile. For my other builds, Marion and Lombard, I had access to full size machines to measure. There are bound to be some of these excavators around here, but it was not worth trying to get access to one.

I am getting the base for the booms pieced together - from the weight of the boom assembly, I am wondering if I'll be able to use the same gear motor for it as I did for inside the booms, given how heavy the parts are. Even with the two cylinders, I may need to go to a larger/more powerful motor for this last one, but fortunately there is plenty of room inside the cab block. May wind up with a car seat motor or something like that. Possible that just another gear set will do - the two cylinders need to be kept in sync, so will be driving both from one motor with a line of three gears, motor on the center one. That gear set could be a 2 or 3:1 combination.

[crueby]

Been doing some work on the excavator the last couple of days, got the base for the boom assembly put together, enough to test the action on the two cylinders that raise and lower the whole thing. Bottom line, I am going to switch out the 4-start leadscrews in those two cylinders to single-start acme thread leadscrews. The weight of the booms/bucket is just too much for the fast-travel screws, and takes way too much torque, too much stress on the u-joints and/or flex cable. So, got some 1/4-16 parts coming in a couple days, wont take that much to retrofit the cylinders to the other parts - can reuse all the cylinder/end parts.

[J.L.]

Hi Chris,

I haven't been on the site for quite some time, but upon returning, I cease to be amazed at your creative skill.  You are a natural as I have often said with metal.

No wonder you participate one several sites. New ideas and projects just flow out of you! 

Take care as we continue in these troubling times.

Cheers...John

[crueby]

Okay, catching up on this side project build - been busy setting up a new computer, and all the time that always takes! Will be better suited for all the CAD work I am doing these days, so well worth the time. Anyway, I got the part in to switch the cylinder pair that holds up the entire boom assembly over to single-start Acme threads vs the original 4-start threads, which were just too aggressive on the movements. Here is the base assembly:

Each cylinder has its own drive shaft - in the picture the one on the right has a small drill chuck on it to make it easier to turn by hand. With the new leadscrews I can turn the shaft and lift/lower the booms with just one cylinder and a reasonable amount of force. Before, that was very difficult. The two shaftws will come back to a common drive gearmotor, have not decided if I'll do a gearbox to link them or use a small chain drive (leaning that way at the moment).
Here is a picture showing the entire assembly, bucket lifted off the table - stays there now, before it could spin the leadscrews and lower itself back, which meant that it would have been putting constant strain on the motors.

Lots of spare shafts and couplers in the foreground from figuring out the whole thing.
Here is a shot showing the part for holding and spinning the cab - there will be a lot of side force at times, so I wanted a strong way to connect things. Wound up with a spare set of tapered roller bearings from a trailer - figure it will be more than strong enough! The gear will be mounted to the track unit underneath, and a motor drive gear in the cab will engage it and turn the cab. There is a slip ring unit there to take the motor leads for the track drive motors down from the cab to the lower unit, but still allow the cab to turn as many full circles as it wants. The spindle will be home made, hollow unlike a normal car axle end to allow the wires through.


I had started this thread a week or two ago when the RC Truck and Construction forum went down - just noticed today that it is back up, but I'll continue here for a little time to seee if they stay alive. Also, the Mann steam truck design is still progressing part by part, got the front axle assembly and boiler modeled up, about to start on the cab and the engine. More on that as it progresses later on.
 

[cnr6400]

 

[Johnmcc69]

 
 Very cool stuff Chris! Keep it coming!

 John

[Roger B]

Another interesting project to try and keep up with     

[crueby]

Thanks guys!
The other forum seems to be staying alive for now, am going to go back to posting progress there again. Will revive this thread if needed - could be their server threw them out since the traffic got so high with everyone staying home and surfing the forums more.
 

[Vixen]

Hi Chris,

It would be great if you could find the time to post here on MEM as well as on the other site.

I think there are plenty of other members silently following your progress, it would be a shame to cut us off.

Mike

[crueby]

Hi Chris,

It would be great if you could find the time to post here on MEM as well as on the other site.

I think there are plenty of other members silently following your progress, it would be a shame to cut us off.

Mike

Fine by me - I didnt want to include a build thread here that was not an engine, but we do seem to have a few going now. I'll copy things in here too...   

[Dreeves]

I for one would like you to post updates here as well. keep up the as usual great work

Dave

[vcutajar]

I'll copy things in here too...

Thanks Chris.

Vince

[crueby]

Sigh. I KNEW I should not let the shop elves near the new computer. They saw the posts about Surus, and taught my old office guard to watch over my bar stock racks. Now I need to give them all Oreo cookies to get another length of bar out.....   

 

[crueby]

Got the sprocket assembly for the chain drive started - using some .250 pitch chain and sprockets from Servo City for these, nice fine chain for small spaces but plenty strong. They sell the master links and link pin removal tool too. I am going to use the same chain for the track drives too. So far have the sprockets on hubs, next will make up a support to hold the sprockets. The output of each shaft will go to one of the cylinders on the main boom via a shaft with universal joints. The input will be from a gear motor onto one of the shafts. So, one motor will frive both cylinders at a matched speed and direction.