Starting a new build... something...

[ChILd_ReBoRn]

So. After a long, long time tinkering with various cable driven machines, and finally setting up a small utility vehicle that I called a Poor Man's Dozer, or PMD for short, i decided to embark on a long journey called RC tech. I have absolutely no experience in RC technics, so I'm a total noob in everything related.

I've decided to build another all purpose vehicle, with a blade, and with a 3 point hitch for some implements. Speaking of witch, I just realized I forgot to order a 3rd ESC for the implement motors. Blah.

So, what do I have already:

flysky 6 ch remote
2 ECS's
2 drive motors (40 RPM worm gear, hopefully enough torque)
4 10 kg servos (metal gear)

I still need 3rd ECS, 11,1V LiPo and some kind of drive train.

My current dozer has heng long plastic tracks from a panzer III tank. They work great, have enough grip, but look silly with a narrow footprint. I found some new ones, rather cheap, plastic or metal ones with a 45mm width, but I'm not sure what sprockets they need.

If I managed to connect everything as it should be, in my head, this setup should work:

blade servo to one channel
3 point hitch servo to another channel.
Left motor to ECS, and ECS to servo and battery.
Same for the right motor.

That leaves me with 2 free channels

One channel would go to another ECS and a jack port for implements (a mower, logging winch and a tipper), and that leaves me with one channel. I think I'd use it for lights or something. How do I connect the lights? is there any kind of an interface or do I directly plug them in into the receiver?

And last thing.. how do servos work exactly? are they always self centering, or are they reliant on the TX stick position?

for an example.. if I put the blade control on a non spring loaded lever, and push it all the way one side, would the servo move to one side and stay put? Would it stop in all positions respectively of the lever position? When I push the directional stick forward, does it work like a throttle? slight push motors moves slowly, bigger push motor runs faster? same as a potention meter regulated PWM?

thank you for now.

I have no fancy tools, nor any money, so this will be a simple build.. no fancy milling and expensive parts, but.. to each his own. As long as it's pushing dirt.. I'm happy :)

PMD V 1.0 (https://www.youtube.com/watch?v=L9XyuhGEYVI&t=67s)

PMD V2.0 (https://www.youtube.com/watch?v=WY9KaVNXOp0)

https://scontent.fzag1-1.fna.fbcdn.net/v/t31.0-8/22792127_10212563336991970_8873083040223601001_o.j pg?_nc_cat=105&_nc_ht=scontent.fzag1-1.fna&oh=8bb5a9f9d5e0bf255416a141370eb576&oe=5CC4A11E
https://scontent.fzag1-1.fna.fbcdn.net/v/t1.0-9/22687840_10212543236809478_3960744273342727284_n.j pg?_nc_cat=104&_nc_ht=scontent.fzag1-1.fna&oh=712fe6206e96769fa55a88cffeb29bf9&oe=5CD10059
https://scontent.fzag1-1.fna.fbcdn.net/v/t31.0-8/22713519_10212543250409818_818527340645652199_o.jp g?_nc_cat=109&_nc_ht=scontent.fzag1-1.fna&oh=143b5dc55061d6bc838bdff263f132dd&oe=5CC85AA6

https://scontent.fzag1-1.fna.fbcdn.net/v/t31.0-8/22791891_10212563336951969_9126727941658940461_o.j pg?_nc_cat=108&_nc_ht=scontent.fzag1-1.fna&oh=4020b56b58715bb32e18264347bf2110&oe=5CCC9984


video (https://www.facebook.com/ChILd.ReBoRn/videos/10212584519801527/)

everything is rather crude, but it's functional. As I said.. only basic tools used :)

[Wombii]

Looks like a fun project! I especially like that control box.

For your servo questions:
Servo angle = stick angle. The servo will move proportionally to the stick. Move the stick to 40% and the servo will move as quickly as it can until it reaches the 40% position and stop. It does not self center unless the stick self centers. If the servo is connected to a channel controlled by a 3 position switch instead of a stick, the servo will move to the 0% position with the switch down, 50% position with the switch in the middle and 100% position with the switch up (The exact positions can usually be adjusted in the transmitter setup with trim, dual rate, mixes and End Point Adjustment).


Bonus technical answer:
Internally, a servo is a motor, ESC and a feedback potentiometer connected to the output gear. The feedback pot works in the opposite direction of the signal from the receiver. If you open the servo and mechanically disconnect the pot from the gear, you can actually control the speed of the motor either with the stick or by adjusting the pot. If you use glue on the pot or replace it with fixed resistors it will work exactly like an ESC and motor. When the pot feedback and stick signal cancel each other out the servo motor stops.
In other words: If stick signal is lower than pot signal then spin motor left. If stick signal is higher than pot signal then spin motor right. If signals match then stop.
Because of this a hacked servo can be used as a motor/ESC combo or a PWM dimmer for lights.

To control lights from a receiver channel you'll need a control board of some kind. This can be a hacked servo, an Arduino, an RC light kit like this (https://www.amainhobbies.com/yeah-racing-dark-drifter-6slot-led-light-kit-w-lights-yea-lk-0002/p632383) or an RC switch like this (https://www.banggood.com/Two-Channels-Controlled-Switch-Remote-Control-Receiver-Switch-For-RC-p-1201647.html?rmmds=buy&cur_warehouse=CN). Frizzen has a great servo light controller hacking tutorial here in the electronics section (http://rctruckandconstruction.com/showthread.php?t=12930).

I hope this helped, but I'm not always good at explanations outside of my own head, so feel free to ask more

[skeeter]

I love the PMD! It's a neat lil budget friendly machine!

[frizzen]

Very cool project! That looks fun.

Each track drive motor only needs an esc, it doesn't need a servo also.

If you want the lights on any time the models turned on you can tap RX voltage and not use a channel to turn it on/off. If you want to switch lights on/off from the remote, check out the links wombii posted.

This will be fun to watch

[ChILd_ReBoRn]

Thnx guys. Can't wait to get the stuff, and start building

[ChILd_ReBoRn]

So, after a lot of thinking, I decided my build would go something about this:

https://www.riverlandequipment.com/uploads/products/518/original/4660.jpg

I really can't fathom why did they make the track setup the way they did, but, since it will put the motors in the back, it will leave a lot of space up front for electronics, servos and battery.

I have a few questions:

1. How do you calculate chassis size? I made it 33cmx16cm, but when I placed the idler wheels I had as spares... they looked ridiculously small, so I downsized the chassis to 24x10cm. That looks small, but since the tracks are 45mm wide, that would give me an overall width of 190mm which is enough, and with the blade up front, it will be around 30cm long. Since my motors are only 8kg/cm (stall torque) better to keep things in the right size department.

How do you make your cabs? I saw people using styrene, but that's way to brittle. How do you mold plastic? or is there another way I'm not aware of?

[Wombii]

I love these forums. I feel like I learn about new machines every week. That is the fastest dozer I have ever seen. https://www.youtube.com/watch?v=N3K9-Mwhd6M

I know nothing about building scale construction equipment from scratch, so I can't help you with the chassis, but I'm curious as to why you feel styrene is too brittle. In my experience it's a very good mix of flexible and strong. I could probably stand on some of the pieces I've made for my fire truck from 2mm plates.

[ChILd_ReBoRn]

um.. when I type sytrene in google, it gives me a lot of sytrofoam links. Including food trays and stuff. That all looks very soft, and breaks easily

[ChILd_ReBoRn]

ok.. I've googled a bit more.. and found what you guys are talking about.. it's some dedicated modeling plastic... that styrene... not sure where to acquire that here...

[ChILd_ReBoRn]

As I said, finding plasticard here in Croatia is near impossible. I'll either order it or make do with something else. It's really expensive for a piece of Styrofoam.

I managed to get the chassis assembled and motor brackets mounted. I can't really do anything else until sprockets and tracks arrive. I will try to figure out how how to make track tensioners.

http://i68.tinypic.com/e7b9d3.jpg

[Wombii]

Ahh, yes. That would explain it. These polystyrene materials are chemically the same as Styrofoam, but completely different in structure. They are not a foam at all. More like a credit card. I've only tried Evergreen (https://evergreenscalemodels.com/), but Plastruct (https://plastruct.com/) is another popular hobby brand. You may be able to find the same material in large sheets from a plastics material distributor or a store for construction materials. I like it because it's easy to cut (score with a knife, then bend to break it off) and makes a very solid bond with a solvent based glue. I don't have experience or a suitable work space for working with metals, but you seem to be good with it. I'm sure you can make a very nice metal cab if you prefer that. Brass is a popular material for detailed work as it can be soldered with normal tools.

This is a good intro to working with styrene: https://www.youtube.com/watch?v=uJQ71o1qqWw

[skeeter]

What You've got made so far for the chassis looks pretty good.

[ChILd_ReBoRn]

Ok. MY Tx came extraordinarily fast. It even avoided customs, so it was really cheap. I managed to mix the channels so moving the stick up both motors drive in one direction, moving the stick down, they both reverse. When moving stick side to side, motors work in alternating directions, so I can steer on a dime. I will see if the need arises to lower the response of individual motors to simulate better steering.

I made the rear idler wheels, and now I have to tackle the front ones. They should be able to tension up the tracks, so they can't be fixed. I'll see will thgey be tensioned by screwing them or with spring loaded system like my old PMD has...Really cant make much progress until my tracks and sprockets arrive. Keep you posted...

http://i67.tinypic.com/2j0not2.jpg

The axles will be shortened when I see the exact track position.

[ChILd_ReBoRn]

Blah. I don't like it. Will redo it. I have a vision.. :D

[ChILd_ReBoRn]

http://i63.tinypic.com/2eoy3ye.jpg

I like this way better.

There are 3 road wheels going between the idlers. Still haven't sourced them..

Will see if they can get some sort of suspension, or will they be rigid.

[ChILd_ReBoRn]

I think the last one is to far to the front. I'll have to move it back and possibly add another road wheel

[ChILd_ReBoRn]

http://i68.tinypic.com/23h0qc6.jpg
http://i68.tinypic.com/15xtvfo.jpg

So, prototype chassis is done. Have to thread the axles when I cut them to size. Decided to go full rigid, like a normal dozer.

[ChILd_ReBoRn]

Weeee.. Got the esc's, Tx, LiPo and xt60 connectors.

Voila.. My first ever RC vehicle.. Lol

http://i65.tinypic.com/311klxf.jpg

My new motors still didn't arrive, so I had to jack the PMD v2.0 for testing.

Reverse is slower that forward movement, and because of the brake, there's a delay while operating motors. A bit annoying. I have to double tap the stick to move the motor in reverse..

[skeeter]

The PMD is looking pretty good!

[ChILd_ReBoRn]

thank you. It's still early to give it true judgement ;)

[ChILd_ReBoRn]

Um, guys.. I need help.
I got my servos today. 10kg/cm. They will be plenty strong, but I'm not sure how to fit them, so could use an idea...

I have several ideas, but not all fit in visually, although mechanically some sound better than the other.


http://i65.tinypic.com/2akbmef.jpg

first option is to place a servo on the side of the chassis, and use a simple lever to lift one blade arm. Both arms would be firmly connected, so when one moves, other one follows. I could add a bogey arm on the other side just to keep the symmetry.

Second option would be to place 2 servos (one for each arm), and splice the wires from one onto the other (Since I don't have that bridge thingy for connecting multiple servos), But I would have to swap the polarity of one servo so both arms would move in opposite directions. That would give me symmetry, double the lift power (massive overkill), and I would mess up my servo cables.

third option is to place a single servo in the middle of the chassis and use a lever system from servo arm to the middle of blade arm connection. So it would pull on the middle, and lift both arms simultaneously


P.S.
How to slow down the servo? I have a feeling it will work way to fast. I saw some speed reducers for servos.. is that the best option?
What do you think?

[frizzen]

That's pretty wild looking.

I'd try to go #3. It won't try to torque it funny like #1, or trying to balance servos or program digital ones like #2. If you want to have blade roll as a feature, then option 2 on seperate channel with mix options.

Many radios have servo slowing as a built in feature, but it's often hidden deep in the menus as a gear or flap thing.

Servo slow
https://hobbyking.com/en_us/turnigy-3-channel-servo-speed-direction-regulator.html?___store=en_us

[ChILd_ReBoRn]

Yeah.. it's wild looking.. I'm making it up as I go. No CNC or a lathe.. so all options are open, LOL...

Ok.. will concentrate on option 3

[ChILd_ReBoRn]

https://youtu.be/DQl8bhZe0uU

I must say that I am very pleased with the servo speed. I limited the range on my flysky, and everything works great. Plenty of torque in that little servo.

edit:

Although this works, I really don't like how it looks. I think I'll go with the 2 servo option. It will look much cleaner, and it will alleviate the need for a big slot on the front of the dozer for the arm to move...

[frizzen]

I was thinking more like blade servo tucked down low between the bogie wheels. Replace nut/bolts holding the blade arms with a T shaped cross-rod, with the center leg of 'T' as an arm close to servo horn length for linkage mount. Maybe square drive / keyway / weld on the ends that the blade supports. Removable bushing plates for the rod if the cross rod is permanent mounted to blade supports.

*i don't know how to build bulldozers*

[ChILd_ReBoRn]

The idea has merit, and I was considering it, although I was opting for a classic round rod to hold the blade arms, and a servo linkage brazed on. That would be clean, but it would put a lot of strain on that little servo.

[ChILd_ReBoRn]

I've gone with the 2 servo option. One servo got "hacked". Resoldered the motor and POT to invert the direction, and I like this much better. More power for the blade...

double servo blade lift (https://youtu.be/nDD0XmpN0nM)

I've added another servo to the back for a 3 point hitch, But since I managed to get the blade rather clean, I really don't like the 3 point look . It's just.. messy. Still not sure will I leave it or not. If I stick to the original M105, I'll lose it and add a winch...

We are now at healthy 1500g without the battery..

[ChILd_ReBoRn]

http://i68.tinypic.com/246mn2q.jpg

http://i64.tinypic.com/htemc5.jpg

[ChILd_ReBoRn]

motors mounted, and mixing tested (https://youtu.be/4lWiOEwhAQU)

Still missing the hazard light, side lights and unfortunately.. Tracks. They are running late.
I've decided to loose the 3 point hitch. Possibly make a winch...

[ChILd_ReBoRn]

Made the blade today. Missing the support struts, and the blade is way to deep. Have to make it shallower. Burned my fingers, and mangled my diy spot welder..

http://i65.tinypic.com/4limc8.jpg

http://i63.tinypic.com/33nf4sg.jpg

http://i65.tinypic.com/1441ylz.jpg

http://i66.tinypic.com/9tij2u.jpg

http://i63.tinypic.com/116o0te.jpg

[Wombii]

Nice compact layout. Looks like a solid shovel lifting mechanism. Good job on the servo reversing too. I didn't think of reversing the motor wires inside.

[ChILd_ReBoRn]

thank you. The tracks came in the post 2day.. finally. Will pick them up, and luckily, mount them 2morow

[ChILd_ReBoRn]

I've cut the blade, and shortened the blade arms. Made some blade supports, had to cut them in half, mounted only on per blade arm. When I fit the tracks, I'll see how much free space I have, so I'll either mount 2 per arm, or make some thinner ones.... I'm off work for 2 weeks, so I'll have to pause the build until then...

http://i67.tinypic.com/nm0too.jpg
http://i63.tinypic.com/i1e9hl.jpg

[ChILd_ReBoRn]

oh the agony.... the sprockets don't fit the tracks... goddamn. I've ordered some custom built... hope they fit...

[ChILd_ReBoRn]

So.. It's been a while. The sprockets were made by a friend. but alas, don't fit. I believe I can grind them to fit, but free time is really an issue last weeks.. so ... easy going...

[ChILd_ReBoRn]

Started on the shell. What can I say.. it's a learning curve. Still a lot of way, and a lot of putty to go....

https://scontent.fzag1-1.fna.fbcdn.net/v/t1.0-9/52047725_10215861648927707_8696776705261436928_n.j pg?_nc_cat=102&_nc_ht=scontent.fzag1-1.fna&oh=454fa1f8bc32570b9edc0efc1e95597a&oe=5CEAF114

[ChILd_ReBoRn]

slowly getting there...

https://scontent.fzag1-1.fna.fbcdn.net/v/t1.0-9/52776058_564009617434529_3989241001200844800_n.jpg ?_nc_cat=102&_nc_ht=scontent.fzag1-1.fna&oh=f83f7bb0213d141e65a457ad863acd41&oe=5CE91428

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[ChILd_ReBoRn]

It lives!

https://youtu.be/VJZ-yw8Kmtc

[ChILd_ReBoRn]

https://scontent.fzag1-1.fna.fbcdn.net/v/t1.0-9/fr/cp0/e15/q65/53194169_571132460055578_214709276302639104_o.jpg? _nc_cat=102&efg=eyJpIjoidCJ9&_nc_ht=scontent.fzag1-1.fna&oh=5b409eb4f78ab803dd181878ccd1a621&oe=5D1C30A1https://scontent.fzag1-1.fna.fbcdn.net/v/t1.0-9/fr/cp0/e15/q65/52967881_571132443388913_7573361763417063424_o.jpg ?_nc_cat=104&efg=eyJpIjoidCJ9&_nc_ht=scontent.fzag1-1.fna&oh=7ef4110ffc0dbe2cac2dc259f052c240&oe=5CE20F6F



I think I have to lower the motors. That will be hard because the mount is fixed, and there's not much free space, but I have to try.. The drive sprocket is a bit too far...

[ChILd_ReBoRn]

https://scontent.fzag1-1.fna.fbcdn.net/v/t1.0-9/53111246_573364439832380_1671730820701749248_n.jpg ?_nc_cat=103&_nc_ht=scontent.fzag1-1.fna&oh=984fc314fbea97366bb30d3b93a8d92b&oe=5D1B8099
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https://www.facebook.com/RCiler/videos/566313257219508/

[ChILd_ReBoRn]

windows are up next, then trims and decorations

[ChILd_ReBoRn]

I might not be a fancy CNC operator, but I try my best using only basic tools...

https://scontent.fzag1-1.fna.fbcdn.net/v/t1.0-9/53619762_577041899464634_4197627892370243584_n.jpg ?_nc_cat=102&_nc_ht=scontent.fzag1-1.fna&oh=b54fb86841289087f0c490723fcde603&oe=5D257F99

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[ChILd_ReBoRn]

https://scontent.fzag1-1.fna.fbcdn.net/v/t1.0-9/53862927_577041939464630_4274895419177172992_n.jpg ?_nc_cat=100&_nc_ht=scontent.fzag1-1.fna&oh=82f50c1a40f664563dfc11023e4bc8f8&oe=5CDBE3F4

[sparkycuda]

Very well done!

Ken

[ChILd_ReBoRn]

https://scontent.fzag1-1.fna.fbcdn.net/v/t1.0-9/53891084_577620609406763_2407114171935096832_n.jpg ?_nc_cat=108&_nc_ht=scontent.fzag1-1.fna&oh=95ad80aa5a33ed51cb1dbd2c62af3b9f&oe=5D1F4B10

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[ChILd_ReBoRn]

https://youtu.be/6RZI0wxy3Wo

https://youtu.be/qbccgrftphQ

I'm not happy with the performance. Reverse speed is way to slow, meaning I need better ESC-s, or even esc and 4s battery. Or try brushless.. Or maybe better quality 370 motors.. If there even is a difference between brushed motors. It has enough torque, but 40 rpm is a bit low with current electronics. 50/60 rpm and dual rate would work wonders.. Just not sure which motors to use. I'm limited to 370 size because of the mounts and worm gear bore...