LR636 Track loader build

[Blender]

I need an easy one, so this is a kit. It won't be stock, but core parts won't be too different. Getting burned out on the long projects.

Enter the Lesu 636 track loader. Looks to be based off Liebherr. I was looking for the smallest machine with the biggest bucket since everybody bought giant dump trailers. Here's the plan:

• Swap all the electronics.
• Swap the hydraulics. They look OK, but ive been wanting to try a specific pump/valve combo. Kampshoff mini pump and Fumotec valves are going in. I've been trying to get one of these pumps in the US for years without success. Luck would have it a newer vender has a few here.
• Add 1x aux valve
• Rebuild electrical tray to maximize battery size. Long run time is the goal. ~90 minutes ideally.
• Jeti radio with the usual telemetry.
• Paint in Sunbelt Rentals livery

Hydraulic system comes pre assembled. Lame. I'll be rebuilding this bracket to hold everything is approximately the same location

Fumotec valve is supposed to use an HS81 servo. It's still pretty big. MKS HS75H has same or better torque and i suspect it will recenter a little better. This is key on a hydraulic valve.

New bracket from 2mm stainless sheet. Tack welded to test fit. Reusing the kit's tank for simplicity. I don't like how high the pressure relief valve's return is. Might foam the oil. I'll add a port to the tank if needed after running it.

Comparison to original layout. Slightly smaller, noticeably lower.

Fit check is ok. in the chassis.

laying out to figure out battery size. Most of my equipment runs on 3S 5000mah lipo. Unfortunatly that won't fit here. Would stick past the front of the seat.

Undercarriage is built box stock. A little paint and swap the kit screws out for better ones. Relaxing to put together.

My favorite ESC. Integrates wth the Jeti transmitter for live setting adjustment via radio. No programming cards or BL Heli firmware flash. Also has live telemetry such as motor rpm, current, voltage, etc The downside is the thing is giant for a 40A. technically it's not even continuously rated 40A. LMR is limited motor run. Very modest. I unwrap it, desolder all the huge 14 awg wires and replace with 18 awg. Power switch was also bypassed. wrapped in Kapton tape which is thinner.

Battery goes here. The included electronic tray blocks half the door which limits this to a tiny battery. I'll fix this

Rough model of the guts. No need to go too crazy. Dropped some sketches to guide me around the chassis limits. If i angle the top of the electronics tray i can fit a 3S 4500 mah 21700 Li ion pack. I've been slowing going away from lipos when possible. XT60 panel mount connector and lots of faces underneither to mount ESCs and the reciever. Doesn't look too bad. Need to notch a few aluminum parts. I've never seen an XT30 panel mount connector. I'd rather use that does anybody know if they exist?

Battery and sheetmetal are on order, then i'll zap it together and see how it fits. Lots of painting to do still.

 

[ddmckee54]

Alibaba has them, and there's also a version on Printables.

 

[RexRacer19]

Cool project. Thanks for posting and sharing on SBG. I recently picked up one of the BMG C308s and discovered your mods thread on RC Groups. I will likely be doing a few of those myself.

Anyway, looking forward to the tracked loader build.

 

[Blender]

Thanks for the tip @ddmckee54. I grabbed a couple via slow boat and we will see how they look. Going to stick with giant xt60 here to keep the momentum

@RexRacer19 Glad to see somebody benefited from that overhaul. I am curious if your machine has all the same performance limitations mine had, or if it's a simple luck of the draw kind of deal. If you have any questions I'll help however I can.

Knocked out the battery holder and electronics tray. My tub measurements were spot on since everything looks to fit as expected. Notched the aluminum body ahead of time on the mill, but I could have gotten away without. Might be able to fit a 3S2P pack in there if I need it.

I was able to find a discharge curve for the Molicel 21700 cells. Being lithium ion they voltage is a bit lower. Full discharge is 2.5V/cell. If I use a 3.0/3.1V cutoff I'll be sitting at ~4000mAH. Still not bad.

Otherwise lots of painting and sanding going on. Able to start some wiring in a bit.

 

[Blender]

Hit the electrical bracket with some black steel-it. Ordered carbon steel parts by mistake. Also did a first pass at wiring. So far so good. Need to adjust some cable lengths.

Fuitek Python motor cables use JST PH3 connectors and the battery port uses PHR-2 both links will also show the right contacts. Still looking for the servo input connector.

Ended up making my own Y coupler for the boom cylinder. Being able to unscrew then to remove the hydraulic power pack will be nice in the future. Bummer is I am out of the right banjo fittings. I could use the kit's included fittings, but I'd rather not.

Test for with some threaded elbows which are taller than the banjos. Fitment is good under the cab.

A couple of the cylinders would bind when traveling through their range of motion. A little bending/prying/filing makes it all smooth.

 

[RexRacer19]

@RexRacer19 Glad to see somebody benefited from that overhaul. I am curious if your machine has all the same performance limitations mine had, or if it's a simple luck of the draw kind of deal. If you have any questions I'll help however I can.

It was a nice thread, and I was happy to see it as build threads like that seem to be a dying art. Not to hijack your loader thread (which is looking great) but I will share my experience with the C308 so far. It is my first hydraulic machine, so I don't have much to compare to. I have the 4-valve machine with the thumb on the stick. I can say that the pump motor gets hot really quick, and has to scream when moving multiple things at once. The boom cylinder moves well, and seems powerful enough, but the stick and bucket move pretty slow. They do seem to have decent power, but to be fair I haven't had the time to really put them to work. Jury is still out on whether the slew will work well as it came or not. Right now, I am thinking of changing the pump motor and redoing the hard lines up the boom to get better flow and a motor that isn't overworked. Where did you source your 2mm barbed fittings for the lines?

 

[Blender]

It was a nice thread, and I was happy to see it as build threads like that seem to be a dying art. Not to hijack your loader thread (which is looking great) but I will share my experience with the C308 so far. It is my first hydraulic machine, so I don't have much to compare to. I have the 4-valve machine with the thumb on the stick. I can say that the pump motor gets hot really quick, and has to scream when moving multiple things at once. The boom cylinder moves well, and seems powerful enough, but the stick and bucket move pretty slow. They do seem to have decent power, but to be fair I haven't had the time to really put them to work. Jury is still out on whether the slew will work well as it came or not. Right now, I am thinking of changing the pump motor and redoing the hard lines up the boom to get better flow and a motor that isn't overworked. Where did you source your 2mm barbed fittings for the lines?

Thanks for the kind words. I too love old school build threads and realize I also need to create some content of my own. I'm still bouncing around forums to find the one that best matches what i actually build.

A little derail is good. I'll take any chance to talk-toys:
Bummer your C308 has the same flaws, must be how they all are. It's a really easy machine to work on though. Sound like you have a good grasp on what it needs. Grap a pressure gage from Mcmaster or the jungle site. It'll really help with troubleshooting. Since it is your first hydraulic machine I will emphasize the importance of a properly configured radio: Valve servo should be well centered with just enough servo throw. A custom curve will minimize the inevitable deadband before the valve actually opens. This can make any valve function to the best of its ability.

Here are the supplies for the 2mm hardlines:

• 2mm Barb fittings best attached with plain leaded solder via an iron. I did add external Flux to really flow into the seam. Didn't bother brazing.
• Brass Tube which bent well by hand
• I've been using this 2mm OD line even though it's not technically rated high enough. Matching fittings here and straights are available too.

For anyone else wondering what we're talking about here is the link.

 

[RexRacer19]

I hear you on the challenge of forums. Even FB groups which killed forums struggle to have good places for actual builders to share. RC Trucks & Construction seems to have died on the vine as well. SBG is generally pretty active but with a small number of construction based builds. I've got a few construction related projects with threads that I need to get going on again as well as making a thread for a CTL that I recently finished.

Anyway, thanks for the additional info about the C308 and a big thanks for the links. I ordered the solder-on fittings last night with some other things I needed for a separate project.

 

[Blender]

While paint is drying it's hydraulic day. The aluminum service disconnect I made for the boom circuit turned out great. Naturally I made a replacement manifold to include the bucket and aux circuits.

DRO made it way easier and faster. I'm no machinist, but it turned out well. Aux circuit (small lines) will be capped at the manifold for now.

The MKS servos are a smaller spline than the stock HS81 so the included coupler was of no use. I originally turned some delrin press on horns , but the square hole was a struggle. Cutting a square on the mill resulted in corners too rounded. Cleaning it up with a file distorted the square. Couldn't find a 3.5 mm square broach, so I cheated and printed these. Nice tight fit on the servo splines and the valve's square drive with a little tapping to get it to seat

Test ran the pump outside of the loader chassis. Motor has a 5:1 reduction instead of the usual direct drive. Pressure relief valve was easy to set. System builds full pressure at 180-230 rpm. Holds steady above. Set at 200 psi here, then I bumped it to 250 psi. Current draw is always a huge concern and the secret to long run time. This pump at low idle pulled ~1 amp. Saw a peak of 2.8A, but I'm unsure how high it actually needs to rev for sufficient flow. Pump will run on-demand once settings are dialed in. Valves hold center well enough to not dripple oil with open ports.

Lunch break now, then plumb the cylinders to the manifold. Should be fully functional later today. May need a little play time as a bare chassis.

 

[zabco]

Really looking good Blender, love the way your fitting everything together. Did you model all these components into CAD to figure all this out or just play around with the parts on your workbench.

I too have been looking for a forum site. I've about decided to make it this one. I started years ago with the old RCT&C web forum which was great. Talk about a wealth of knowledge! Then FB came along and everyone wanted to be able to post photos and videos instantly and the old web site fell into disuse and, I think, is now gone for good. Shame, I have a huge 3-ring binder full of tips and techniques I copied and saved from that forum for future reference and ideas. FB is just not conducive to multi-step build threads. Some guys tried but gave up and the FB RCT&C page has turned into nothing but a sales venue and guys hyping their youtube channels so they can make money on your visits. I still visit just too see show postings but couldn't tell you when I last posted anything. Other sites I've looked at are all also lacking in participation anymore, probably also due to FB.

 

[Blender]

Really looking good Blender, love the way your fitting everything together. Did you model all these components into CAD to figure all this out or just play around with the parts on your workbench.

I too have been looking for a forum site. I've about decided to make it this one. I started years ago with the old RCT&C web forum which was great. Talk about a wealth of knowledge! Then FB came along and everyone wanted to be able to post photos and videos instantly and the old web site fell into disuse and, I think, is now gone for good. Shame, I have a huge 3-ring binder full of tips and techniques I copied and saved from that forum for future reference and ideas. FB is just not conducive to multi-step build threads. Some guys tried but gave up and the FB RCT&C page has turned into nothing but a sales venue and guys hyping their youtube channels so they can make money on your visits. I still visit just too see show postings but couldn't tell you when I last posted anything. Other sites I've looked at are all also lacking in participation anymore, probably also due to FB.

First I mocked up with physical parts to ensure it was close, then I blocked out key parts in solidworks and created the sheet metal parts. The tub is very rectangular, so I use a few simple sketches as a visual boundary.

Bummer that the hobby is biggest and most accessible as ever while interaction is at the lowest. I have been slowly learning German to take part in the European forums. Initial response is favorable, but I'm a long ways from writing about technical subjects. "Der hund ist sehr groß." 'Das essen ist heiß." My Spanish is much better.

I did get the machine running last night. Valves are nice, their quality is apparent. Same with the pump, although I'm not used to the high motor rpm sound due to the 5:1 gearbox. I did find a flaw the in Z bar mechanism. When the bucket is curled back and the boom lifted or lowered through a specific point the system can bind. Each linkage independently moves smoothly independently, but a few combinations require the bucket cylinder to relax or drift.

In my case the bucket cylinder line blew out while the boom was lowering. Never seen one of the 2.5x4mm nylon lines go like that. The strength of the twin boom cylinders induced super high pressure against the bucket's closed valve. Squirted directly into the pump ESC, but it survived. I was wondering why the kit comes with a secondary double pressure relief valve for just the bucket cylinder. This is downstream of the system pressure relefe valve. Now I know this was added to allow the bucket cylinder to move despite the valve being closed. I'm not going to add this parts in, but instead attempt to actually solve the geometry shortcomings.

B1 through B4 ports are the secondary PRV. I suspect it simple bypasses into the other line to allow the piston to drift as needed.

Ended up making a wrench to get the cylinder apart. Normally they are not that tight and can be disassembled without special tools. Smaller hole pattern is for the boom cylinder caps.

After removing the hydraulic valves and hand cycling the boom I settled on adding a 4.5mm thick brass spacer to the bucket cylinder. It's installed here. Further hand cycling looks like this helps, but I'll need to re assemble everything to test. Doesn't reduce bucket curl when the arm is low since the cylinder was capable of over traveling. I will loose some curl at high boom positions. Full dump travel is preserved.

Long term I'd like to measure the mechanism well enough to create a 2D model and look for a true solution maybe a different rocker in the Z bar system.

Still cleaning up all the oil that is everywhere

 

[Schneegeist]

Your solution to take apart the cylinder is smart. I'm sure someone makes a tool just for that, but it's probably at least a boat across the pacific away. I'm curious if rc hydraulics require a lot of tinkering to keep running nicely. I see all those tubes and hoses and fittings and I see potential problems, but I'm a noob in equipment.

 

[Blender]

Your solution to take apart the cylinder is smart. I'm sure someone makes a tool just for that, but it's probably at least a boat across the pacific away. I'm curious if rc hydraulics require a lot of tinkering to keep running nicely. I see all those tubes and hoses and fittings and I see potential problems, but I'm a noob in equipment.

Thanks. I knew I had one pin wrench, but it was way too big. The usual vendors didn't have the right size either. Took under an hour to make.

If a hydraulic system is well paired and consists of high quality components it can go years with no issues. Just needs the oil changed regularly. One of the local guys has a rc wheel loader that is over 20 years old. All original hydraulics with just oil changes. My excavator only 4 years old, but has been solid so far. On the other side of things I've had an import no-name pump that was burned up in a few months.

The hoses are a pain since everything is barbed and has a collar. They must be cut apart. That's the main reason I use banjo style 90 degree fittings. They are able to be unscrewed without twisting the hose. Great for service. I try to organize the model interiors to keep the electrical above where any oil would collect. You'll also notice I didn't paint the inside of the track loader chassis because I like to use brake cleaner to break down spilled oil. Hydraulic is a pain at times but the performance is worth it.

 

[Schneegeist]

Thanks for the great explanation! It's always fun to learn new things

 

[Blender]

Got more of the body together. Nothing interesting there, it's box stock. I did look into the Z bar performance a bit closer:

• At low boom position max curl back is ~35deg. As the boom goes up this increases by 7-8 deg. That's fine.
• If the bucket floor is held level at low boom position the bucket will uncurl by almost 20 deg as the boom raises.

The z bar does not work as well as the much smaller MCL8's linkage. It will hold the bucket curl steady through full range of boom travel, at least to visual accuracy. This is much easier and predictable to operate. Adjusting the linkage performance is now my next task.

 

[zabco]

Linkage systems can be very tricky to design. Change one length or angle here and it throws off another over there. It's a balancing act. There is some free software available that I have used a couple of times that is designed for creating linkages. It is called "Linkage Mechanism Design and Simulator" written by a man by the name of David Rector. It has not been updated is a few years but it still works fine. Takes a bit of a learning curve and I always have to take time to remember how to use it as I don't use it often enough to remember how it all works. I have it installed on a Win 11 pro laptop and it runs fine. Has a number of sample files so you can see how it works. Very interesting to watch the animations it can create. Available at: https://blog.rectorsquid.com/linkage-mechanism-designer-and-simulator/

 

[Blender]

Linkage systems can be very tricky to design. Change one length or angle here and it throws off another over there. It's a balancing act. There is some free software available that I have used a couple of times that is designed for creating linkages. It is called "Linkage Mechanism Design and Simulator" written by a man by the name of David Rector. It has not been updated is a few years but it still works fine. Takes a bit of a learning curve and I always have to take time to remember how to use it as I don't use it often enough to remember how it all works. I have it installed on a Win 11 pro laptop and it runs fine. Has a number of sample files so you can see how it works. Very interesting to watch the animations it can create. Available at: https://blog.rectorsquid.com/linkage-mechanism-designer-and-simulator/

Looks like some neat software. Free too which is great. I'll be doing the manual method: Plotting out the design graphically in SolidWorks. At least to start. A quick drag through the range of motion. At work I'd spend a day or two and write equations to track critical points through 2D space, then calculate lift and curl force every 1 degree. And make graphs, that nobody looks at except me.

Side note, there are two rc truck shows coming up. California trucking show, and a digging event in SLC. I'm super excited even if it is a lot of time in the car. More playing than building for a few weeks.

 

[ddmckee54]

Took me several days and many 3D model designs to get the door hinge to have the proper range of motion and still fold into the available space on my RT7R. I'm running an older version of Alibre and if it has the ability so show interferences I haven't discovered the secret handshake yet. Gonna hafta take a look at that linkage program.