Go Back  R/C Tech Forums > General Forums > Rookie Zone
How to make a custom build for robot? >

How to make a custom build for robot?

How to make a custom build for robot?

Old 05-19-2020, 12:12 PM
  #1  
Tech Rookie
Thread Starter
 
Join Date: Jan 2020
Posts: 3
Default How to make a custom build for robot?

Hello all!

I'm working on a open source sidewalk/delivery robot and was wondering if I could get some advice on the RC design side of things (I'm a lot better with software than hardware).

The current setup is with a Redcat Shredder V2 which has worked OK for testing but has a few serious shortcomings:
1. It comes with a sensorless motor/ESC. This makes it really hard to control at low speeds.
2. The springs for the shocks buckle/fully compress when cargo (such as a cooler) is added and I have to replace all of the shock springs with stiffer ones (not the end of the world)
3. It seems to rust with prelonged use.

Of those problems, the sensorless motor/ESC is the one that causes the most issues because it's nearly always operating at low enough speeds that the controller is having issues. Since it's an RTR kit, if I have to replace the ESC/Motor I will have to pay for essentially two motors/ESC ever time I make one. If I may ask, does anyone have any advice on how to get/make something but with a sensored motor/ESC at a reasonable price? Alternatively, is there any practical way to fiddle with the gearing to make it do more turns at low speeds? It really doesn't need to ever go faster than a light jog.

Thanks!
Charlesrwest is offline  
Old 05-19-2020, 08:17 PM
  #2  
Tech Addict
 
Join Date: Jul 2018
Location: Florida
Posts: 713
Default

why is it hard to control at low speed? cogging? cogging is less of an issue at higher rpm. if that means twice the speed to you then double the ratio so you use more of the motor rpm.

it ill probably cog less if the magnets are weakened. but then you will lose torque. heat weakens magnets.
Bry195 is offline  
Old 05-20-2020, 11:26 AM
  #3  
Tech Master
iTrader: (9)
 
IndyRC_Racer's Avatar
 
Join Date: Jul 2006
Location: Indianapolis
Posts: 1,937
Trader Rating: 9 (100%+)
Default

Here are some quick suggestions...

1. Sensored brushless motors OR brushed motors should provide better low speed control. You may also want to look into sensorless rock crawling motors.

2. Could mountain bike suspension/springs be used or modified to work on that vehicle? Don't limit your options to r/c parts as they may not be strong enough for your application.

3. You may need to replace hinge pins and screws with stainless steel. You could also coat the metal parts with paints that will help with rust/corrosion. Companies such as Krylon or Rustoleum sell inexpensive paints designed to prevent rust.
-The corrosion you are seeing may not actually be rust but it may be oxidization. If your parts are made from aluminum they can experience corrosion from exposure to salt, oxidization from exposure to oxygen, or galvanic corrosion which occurs when 2 dissimilar metals come in contact. There are 3 simple ways to protect aluminum which are painting, powder coating, and anodizing.

(4.) A RTR kit by definition is Ready To Run. These kits typically include items such as motors. If you want to choose your own motor, there are plenty of kits by various manufacturers that you have to build yourself or kits that do not include electronics. You can always contact the r/c manufacturer and see if they could build out a vehicle to your specifications, but I would assume that you would have to purchase a large bulk order (expensive)

(5.) Gearing on almost all r/c vehicles is something you can adjust by changing the spur or pinion gear. You may be physically limited to the size of the gears you can use depending on how much space you have available.

----------

What I'm going to type from this point on is not meant to discourage you from your project. You have admitted that you are a software guy, so don't try to reinvent the hardware. Just make existing hardware work better with your software. By doing a quick google and internet search I found several examples of remote controlled coolers. I've also found several designs that can be sat on and driven. I would suggest looking at the platforms that these vehicles are based and see if they could be perhaps modified for your purpose. What I think you have already discovered is that most hobby grade off-road r/c vehicles are a poor platform to use for hauling weight. This is mainly because these vehicles are designed to be as light as possible. Their suspensions are designed to handle the weight of the car only as it goes over bumps and jumps. While these vehicles can always be modified to perform differently, too often the time and cost involved could spent on a better platform. However since you didn't give us the exact weight or volume of your payload, an off the shelf r/c vehicle may very well be suited to solving your need.

Based on your post, it sounds like you want to have your payload on the actual r/c vehicle itself. Is that the only option? Could the r/c vehicle act as a tow or push vehicle? Could you tow a 2 wheel rolling nylon cooler easier than placing it on top of an r/c vehicle? What would the challenges be for mounting a tow hitch?

My final suggestion would be to look at existing vehicles or platforms that could handle the maximum weight of your payload. It may be far easier or cheaper to add r/c controls to a scooter, go kart, or push/pedal toy than to modify an r/c vehicle to haul heavy objects. You should consider looking into motorized wheel chairs or mobility scooters as these types of vehicles have powerful motors and rechargeable batteries.

I may be over-thinking what you are trying to do. Please feel free to provide any additional information and I'm sure someone in this community might be able to offer additional suggestions.

Good luck and I hope this information helps.
IndyRC_Racer is offline  
Old 05-20-2020, 06:58 PM
  #4  
Tech Rookie
Thread Starter
 
Join Date: Jan 2020
Posts: 3
Default

If I could get hardware that would "just work" and let me focus on the rest of the system, I would love that. Don't worry about injuring my pride!

I followed up on the RC cooler suggestion and the main entry I found was C3 RC coolers. They look really interesting, but I'm not sure how well they would hold up to actual continuous daily use. I intend to reach out to ask them some questions regarding their platforms and possible partnerships though (thanks!).

The original intention was to have the payload on the RC vehicle so that one platform could be used for different purposes (the training data is somewhat vehicle specific). The other concern is that a tow arrangement might have more trouble with uneven/off road paths (the golf course I've been testing at has some deep puddles and bumps).

The main problem with going full human capable vehicle is expense and added hazard if something goes wrong and it hits someone. The control electronics are only ~$200 or so once all is said and done, so I was hoping to keep the construction cost of the mechanical/battery side of the vehicle down to ~$300-$500 for a sale price of around $1000.

Is there any established path to getting something like this designed?

I'm hoping to scale my capital outlay as I reduce uncertainty concerning if I can sell/rent these things... Target: one on a golf course, five on five golf courses then something professional enough that someone else can use it without me having to personally oversee things.

Also, thank you!
Charlesrwest is offline  
Old 05-21-2020, 11:01 AM
  #5  
Tech Master
iTrader: (9)
 
IndyRC_Racer's Avatar
 
Join Date: Jul 2006
Location: Indianapolis
Posts: 1,937
Trader Rating: 9 (100%+)
Default

I'm just brain storming, but why not consider using an electric kids ride in or on toy as a base for your vehicle? The bodies on these vehicles are made from plastic, are powered by 12volt batteries, and can normally accomodate a rider of at least 50lbs. In the past week I saw one of the local kids in my neighborhood riding his electric tractor through the sloped grass area by a local pond (he was being supervised by an adult). I have no idea what the range is on these vehicles, but they have a very limited top speed. They are also noisy enough when running that most people would be able to avoid being hit by them. Many of these vehicles already have steering wheels or mechanism that should be able to be modified to use a steering servo. You can find plenty of videos online of these types of vehicles being modified. While these vehicles have limited suspension travel, they do come in variants such as golf carts or monster trucks and off-road vehicles that sit higher off the ground. The only challenge with these vehicles is that they have plastic wheels that might not perform well in low grip situations. You can purchase these types of vehicles online or at most Wal-Marts stores for under $300 USD.

Another platform that I've thought of is electric powered skate boards. There are various versions of these types of boards including offroad mountain boards. They also sell electric conversion kits for existing skateboards that have the electric motors contained in the wheels. This type of platform might give you some ideas how to design your own system.

One final thought for now is using PVC pipe to build your own DIY vehicle. The below video is an example of someone who built an electric "go-kart" using PVC and wood.
IndyRC_Racer is offline  

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are Off


Thread Tools
Search this Thread

Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service - Do Not Sell My Personal Information

Copyright 2018 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.