Michigan T-24 project

[jerry56]

Ok it's time to try this one.
I think I know enough to be dangerous so here I go...
I have a couple of these I've been picking up over the last few years and this one was the worst of the bunch so I picked it to be my prototype...
There was no way I was going to be able to clean it up enough to paint without a sandblaster and even then I'm not sure how it would look... SO I'm going with "patina" on this one...



First thing I did was get it stripped down


To make it manageable I divided it into three or so pieces, the carrier, the crane house and the boom and buckets. I'll probably do a dragline bucket and attempt a clam bucket....
But first the carrier....
I'm going to use WPL axle assemblies and a 3d printed dual motor mount.
But first I need to cut away these two stiffing rails because they are about 6 or so mm to close together




I went with this stye because to me they looked beefier than the regular WPL axles






I did a sort of walking beam type suspension vs leaf springs because I figure this is going to weigh around 20lbs and figured the springs would just bottom out. I don't think I'll need a lot of flex since this isn't a rock crawler


This is the basic layout, I cut some aluminum angle to fit around the different ribbing and joints in the carrier frame. The rear walking beam sits just outside the toys frame stiffeners so I bolted it all up to my new frame rails and set it in place. The motor mount is the same width as the WPL running gear so it all lined up...
The problem came with the front axle it mount on top of the frame rail unlike the rear that mounts between it.
So I cut it down to the size I use for my Tonka trucks and turned the angle over and bolted it thru the existing metal in the front there is enough room to bolt thru the frame

The motors are 500rpm feeding thru the WPL axles which are 2 to 1 ratio that gives me about 250 rpm at the wheels

I haven't decided which wheels I'll use so I just stuck some on it so I could see how it sits.



I need to figure out how I'm going to wire this thing up, but I'll work on that this week...

[frizzen]

Are you sure sandblasting is NOT supposed to be part of the rc hobby? (I like using Black Diamond slag media)

I'm really digging the looks of those axles under the carrier! Good call on walking beam, your going to want all the stability on axles for swinging a boom around unless you also add a set of front or midship outriggers.

Looks like you're on a really good path, I'll definately be taking notes on many parts of your conversion.

[jerry56]

Typically I would clean it up and paint it, but this one was really bad it would be pretty pitted. When I pulled the rusted up headlight button it just crumbled ....
I started to use the WPL springs I even doubled them up but you could tell the truck was going to be way to heavy and it just wobbled around the walking beams are way more stable. I used springs on the front but they are stiffer and seem ok so far... I toyed with the idea of adding another set of out riggers but it was looking a little to involved, maybe on the next one...
The carrier is coming together faster than I thought it would... LOL.. notes on my conversion...I've studied yours and RVjim's builds for a couple YEARS still stealing ideas... as you will soon see

[frizzen]

Well yeah, if any of us were that concerned about sharing ideas, we'd be those racers at the tracks who never pull the body off so you don't see their winning secrets.

I had a cunning plan: Start a toy conversion, document heavily in hopes someone is eventually inspired, get stuck, let them hopefully figure out the parts i stumbled at, and try to ride their coat tails to victory

Since some of yours crumbled, the Headlights are "chrome 1/2" hole plugs" many hardware stores carry them. I believe Doepke fire trucks used same size if you wanted new reproductions with the lens part cutout for adding lighting.

For the front end I had wondered with the expected final weight, if something like 1/14 Semi truck leaf helper-springs added on your wpls might help?
Maybe 4-link with something like fueltube or stack of O-rings acting as elastomer springs?
Cross drill a 4-link mount and hang from ballends for pendulum axle like original toy had?

[jerry56]

Well I hope I can inspire you to get some running gear under yours..LOL
Yeah I knew about the hole plugs, but I'm going to make some head light buckets I hope... then use wiggly eyes for the lenses.
I doubled up the front springs and they are pretty stiff, if they still seem wobbly I'll probably just mount them solid

[ddmckee54]

Fuel tubing is do-able as a spring, but it's a lot stiffer lengthwise than you might think. When I built the rotary valve for my dust collector I was using springs 3-4mm in diameter to keep the vanes pressed against the valve body as the vanes rotate, wasn't stiff enough. Then I also got the bright idea of using silicone fuel tubing. I found out that if you don't support it properly that crap will just fold sideways. Took a couple of redesigns of the vanes and rotor to get it right.

Once you get the tubing restricted so that it has to compress lengthwise that stuff is remarkably stiff. I had to limit it to about 2mm of compression lengthwise. Any more than that and my motor couldn't turn the valve anymore. A couple of pieces of telescoping tubing the right size and you might be able to make a "shock" that's actually the helper spring.

Don

[jerry56]

Hmmm not sure I'll need to go to that extent for this one but I like the idea, I can see where it might come in handy....

[jerry56]

Ok.... I got the steering worked out, I used a short 12kg servo that mounted up all the way up front and pretty much stays hidden behind the front bumper.



The motors were sitting a little low making the driveshaft angles a little steep so I just made some mounting plates to lower it a little.



The layout is pretty clean... until I start running wires all over


View from the front, looks pretty good I think.


Now here's the plan... I'm using the Huina 1550 slew gear setup with a 4 wire slip ring, I'll have 3 functions in the carrier, steering, fwd/rev, and lights.
I'm going to have separate power for the carrier and the crane house. I'm going to power everything in the carrier with one (or two)battery and just run the signal wires and a ground thru the slip ring to the receiver. Then power everything up top with another battery or two. I connected all the signal wires thru a terminal block to the slip ring then connected it all to the receiver on the other side


I did a quick test and it all works, so far so good. It drives and steers so the carrier is figured out just need to finish up and clean up the wiring.

Now time for the house.. Like I said I'm using the huina 1550 excavator slew gear and slip ring set up, I like this one because it has a wide flange for the house to bolt to making it really stable

But first I need to get some stuff cut away, I drilled out the spot welds and then used a chisel for the tough ones

The slew gear has a shouldered section that needs about an 1 1/4 hole so I just used a hole saw and cur it out






Now the back cover needs to come off, again I just drilled out the spot welds and took it apart.


I only got carried away with one weld...


The shoulder on the slew gear came out past the front of the house just a hair... in later versions I may try and move it back.. but one has to be careful because if you go to far the counter weight will hit the cab.


The nice thing is with the gear installed the house sits at the same height as the original toy..



I 3d printed a simple dust cover for the slew gear, it doesn't seal it up but it should help keep dust and dirt from flying into the gear.



it also cleans up the area underneath.


This is moving along pretty well, I haven't had any major problems so far...Thanks in large part to you guys that have already done this and gave me great information to get me started.
I do have a question though.. I want to be able to run 2 batteries both in the carrier and the house. The house will be capable of running 2 4200AH Nimh batteries. But underneath I was going to run 2 LiOn ( not LIPO) I don't think it will matter but since LiOn use a balance plug for charging can they still be wired in parallel. I'm pretty sure it won't make any difference to the battery but wanted to ask.

[ddmckee54]

Using two different flavors of batteries you'll have different discharge curves. I think you'll need to tie the commons (-) of both battery packs together so all of the electronics will have the same zero reference. Also be absolutely sure that only the signal leads are shared between the house and the chassis electronics. Otherwise, as the packs discharge the higher voltage pack will try to charge the lower voltage pack through the electronics. This usually results in letting the magic smoke out of something.

[jerry56]

ddmckee54... Thanks...I was just making sure..
The batteries in the carrier are the same, both LIon both 2000mah.
I only have signal wires going from the carrier to the house and a single ground wire from the esc, When I was experimenting with this I found that it won't work unless you run a ground back to the receiver from both circuits.
The batteries in the house are 4200mah Nimh they are kind of heavy so I use them as part of the counter weight.
Both sets of batteries are paralleled into a power block so each circuit should only see one power source from their respective batteries.. if that makes sense

[frizzen]

Great looking progress!

That's a really slick idea with the seperated power sources sharing signal through a slip-ring! I don't remember seeing any crane models done that way. I knew you needed to bridge the Ground so the Signal pwm has a solid reference value.

With this size machine I wasn't sure how much you'd really want/need to intermix your drive and crane functions? Might get interesting without having powered outriggers.

[jerry56]

Yeah Frizzen...
When I first tried it I hadn't used a ground wire and it doesn't work it has to have the ground reference.
That intermixing was the problem, I steer with ch5 on a rotary switch on the I6 ( an old smallhaul trick) but I use ch2 for forward and reverse. But I needed a boom up/down so I put it on ch9 on the 3 position switch since it doesn't seem to get used that much once you are set up. Slew and load up/down are on the other stick so far it seems to work for me...
Ahhh the out riggers... I just haven't come up with a simple way to do them ( and I'm all about simple)... If I figure something out I might just use a key fob for the outriggers

[ddmckee54]

The outriggers might not need to be powered, just pull out and crank down? But they definitely need to be functional and not just a pad resting on the ground. Otherwise things could get a little tipsy, and not in a fun way.

[jerry56]

Agreed ddmckee54 it would be tipsy...lol... they will work but they will be manual. I thought about some kind of rack and pinion to move them in and out but then you have the issue of how to make them go up and down.... and how to keep the wiring for that from getting cut up or rubbed bare just more than I'm going to tackle at this point.
I double checked and the motors I used are 6v 200rpm so running at 7.4 that should be close to 250rpm with the WPL axles at 2:1 that gives me about 125 at the wheels... not super fast but in real life this thing never was...

[jerry56]

I worked on the cable drums and boom this week...I built a drum assembly like Frizzen and RVJim and it went in with out a hitch.... sort of ...



Both of those builds used a large diameter slew gear that put the slew motor further off to one side so it didn't interfere with the drums.... I used the Huina 1550 slew gear that is way smaller and it put my slew motor in way closer, actually the only place I could put it was dead center under the drums.
This didn't leave any room for the lower front drum I tried grinding and sanding the motor case down but couldn't get enough clearance. Then I tried moving the lower drum up but as it goes up it also moves back so the clearance got worse. I even tried making the drum smaller but it just wouldn't clear. So I figured I would move it forward and down... I printed some plastic angle the same dimension as the aluminum I'm using so I could cut/drill/tap it so I didn't waste my aluminum and it's way quicker to cut...Once I got the postion right then I cut my aluminum and mounted everything


So moving it down and forward got me enough clearance for the lower drum but if I left all three together the top drum was way to far down and forward so I had to split them up


I put a bar across the bottom to help stiffen the whole thing up


Then made a new mount for the top drum so it would sit where I wanted it to for my boom hoist.



So once I had the drums mounted I cut my hole for the boom cable and made the support brackets for my pulley assembly. You can see the slew motor in the center. I'll have to cut the front lip of the cable house down a little so the cable can feed out when it has a dragline bucket on it.
I'm planning on an 8 part line to a pulley block then just single cables on either side out to the boom tip.

[frizzen]

That really sucks about the slew gear motor. Going by the slipring cutout, I thought it could fit over on left side of machine in the engine / counterweight area? Also depending on your cable drum servos, you might be able to get some extra space by relocating the pcb and trimming away some extra plastic

All the rest of it looks like you're making awesome progress!

[jerry56]

I angled things and trimmed plastic off stuff and sanded and grind-ed on the slew motor case... I angled stuff there was just no other place to put it then right in the center... Which by the way has a "hump" pressed into the metal on the bottom of the toy so that had to be cut out so the slew motor would fit flat... Luckily so far this has been the only real issue I've run into....
And your right this build is coming along way faster and way smoother then I thought... so far...

[jerry56]

Well now that holidays are over and I'm getting back into finishing this project up.
I needed to get the boom cleaned up, the pins were really sloppy and I wanted a dual sheave in it. The pins in the boom are about 3.7 mm so I drilled out the two boom pins in the middle, the pin in the boom tip and the one in the base to 4mm and made pins for them so now it was nice and solid.
For the boom tip I made some spacers. They wont have a torque or pressure on them so I just took some plastic sheet (1mm I think) and drilled 2 4mm holes in it and simply cut them out then cleaned them up a little, they won't be seen so no need to get to crazy whit them


Then I laid out the rest of the pieces I put some flanged bearings in the PLA+ sheaves. Then I used some 18ga wire ends for the 2 main cables running back down the boom... I spread the wire ends open enough to get the Kevlar string in them then soaked them in super glue and closed them up then gave them another soaking then trimmed them up. They are rock hard and no way will they pull thru.




I gave the boom a quick coat of blue paint and did the tip in Chrome yellow


This was before I cut the pins for it.


I got these at Hobby Lobby to connect to my cable block




And these for the cable loops.

These were to soft to hold under any stress so I just put a little dab of solder on each one.
So now were getting ready to string this thing up.... I made a riser for the 4 cable pulleys that's just a little taller the the stock toy .



Looking down the boom ..


and another shot..


I'll get some more pictures in a little bit... But everything on the crane works I just need to get a dragline bucket put together ( have all the parts I need) and I want to get a clam shell bucket working...just need to get the mechanics worked out..I've been studying what you guys have built....Then I need to get the lights and some other small details made and put in....

[frizzen]

I really like the cable bridle on the boom luffing cables, that looks sweet!!!

Great idea using ring-terminals! If feeling really crazy you could probably make those into a Wire Rope Wedge Socket, so the free end hangs out away from the eye.

Don't let lack of a digging bucket slow you down, you can throw a headache ball & hook on there and start lifting stuff right away.

[jerry56]

I was really happy with the way the cable bridle came out and the way it looks.
I could have left a little string hanging but I trimmed it up close... no real reason, I just did.
I got the same RC4wd hook you did and a lead fishing weight, just little details I need to get finished up... I also have a reproduction Tonka drag line bucket and all the parts to get it strung up.... I'm close...Also looking for something "different" to lift....not sure what yet.