Author Topic: Scratch built giant rc car  (Read 15979 times)

Offline KB

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Scratch built giant rc car
« on: September 11, 2013, 03:51:07 AM »

I haven't built any model engines lately, but I have done a bit of model engineering.

Rear differential and drive-train;













Servo saver and steering linkage;







Shocks,



















Various parts;















Coping a tube in the lathe;









Hopefully, one day, it will all come together to look something like this;










Have fun out there!

-Kevin



Offline metalmad

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Re: Scratch built giant rc car
« Reply #1 on: September 11, 2013, 04:18:49 AM »
Wow, How nice is that
Love it  :praise2: :praise2:
Pete
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Offline swilliams

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Re: Scratch built giant rc car
« Reply #2 on: September 11, 2013, 06:38:09 AM »
Innovative and cool  :ThumbsUp: :ThumbsUp: :ThumbsUp:

Steve

Offline steamer

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Re: Scratch built giant rc car
« Reply #3 on: September 11, 2013, 11:04:54 AM »
Wow Kevin!    What is powering that beast?......looks like a quad bike engine and transmission! :o

Dave
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Offline MuellerNick

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Re: Scratch built giant rc car
« Reply #4 on: September 11, 2013, 11:48:23 AM »
Quote
What is powering that beast?


Looks like a Honda Monkey (or SS 50) knock-off engine (available with more than just 50 ccm). Cheaply available from China.


Parts look very professional made!




Nick

Online b.lindsey

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Re: Scratch built giant rc car
« Reply #5 on: September 11, 2013, 12:15:01 PM »
That is really some amazing work there Kevin. Beautifully machined parts too!!

Bill

Offline V 45

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Re: Scratch built giant rc car
« Reply #6 on: September 11, 2013, 12:41:34 PM »
Again Kevein....GREAT WORK !! That will be pretty cool for your son to crash  :naughty: !! But by the looks of the construction he'll have a hard time doing it !!
  Dave
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Offline KB

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Re: Scratch built giant rc car
« Reply #7 on: September 11, 2013, 05:00:34 PM »

Thanks a lot everyone.

Yes it is a Honda clone. I believe Honda started producing these engines when they came out with the Cub or Passport. The most produced motorcycle scooter in history.
The one I have is a 70cc, 3speed auto. It came from a Chinese quad I was given. It needs a complete rebuild. (think disposable engines) I think up to 110cc uses the same crank-case.

I put a real Honda, 70cc, 3 speed, manual in this contraption;






Quote
That will be pretty cool for your son to crash  :naughty: !! But by the looks of the construction he'll have a hard time doing it !!

I'm not too worried about the car, but whatever gets hit! I'm going to try and set-up a triple redundant fail-safe/ kill switch system. 2 electronic and one mechanical.
I should probably take out an insurance policy too. It will be about 4 feet long and weigh well over a hundred pounds.

Cheers!


Offline Tennessee Whiskey

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Re: Scratch built giant rc car
« Reply #8 on: September 11, 2013, 06:57:41 PM »
Looks great Kevin. I love the "huge" RC stuff. Aircraft with 8' wing span and this kind of stuff.  Dave, this thread may need to be off limits to William. I'm waiting on a Wallaby 8)

Whiskey

Offline smfr

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Re: Scratch built giant rc car
« Reply #9 on: September 11, 2013, 07:41:06 PM »
Wow, awesome stuff!

The front end looks a bit fragile. Any reason there aren't struts across the very front of the frame? Or did you just slice off the front for the rendering?

Simon

Offline jwcnc1911

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Re: Scratch built giant rc car
« Reply #10 on: September 11, 2013, 09:42:50 PM »
This is freakin awesome!
----------
JW

Offline KB

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Re: Scratch built giant rc car
« Reply #11 on: September 12, 2013, 04:59:01 PM »

Thanks all,

Simon, You are right, there will be cross bracing up front and a bumper of some sort. I just didn't work it all out ahead of time. I want to make sure I am happy with the steering linkage before I fill it in.
Also I may need room for a battery and electronics, maybe the fuel tank as well...

I made full size templates for bending.

First set my very expensive angle o' meter;




Then set the starting point of the bend. A sample bend is marked to a corresponding mark on the benders' die. It is placed so that the bend touches the outside of the bend and the mark is transferred to the template;




Then the mark is transferred to the stock;




Then into the bender and bent to the previously set angle;




Then it is notched and back to the template to be marked for final trimming;





I don't have a proper bender, but your standard import bender for which I have made quite a few dies.


For pieces too large to fit the lathe I have this tube notcher, which I made a long time ago;






Cheers,

KB

Offline KB

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Re: Scratch built giant rc car
« Reply #12 on: February 27, 2018, 04:08:47 PM »
Well this project was shelved while I raised my two sons, racing BMX with them and doing a lot of home renovations.

It is time to get back out in the shop!









.

Offline Vixen

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Re: Scratch built giant rc car
« Reply #13 on: February 27, 2018, 04:30:48 PM »
Hi KevinB

That's an amazing vehicle. A full size racer, but in miniature.

I watched the video and have a question about that steering servo. It looks like you are using a window winder motor with a slave servo to give position feedback. Am I correct? The next question is about what are you using for the electronics module. Who is the manufacturer ans supplier?

Mike
It is the journey that matters, not the destination

Offline Allen Smithee

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Re: Scratch built giant rc car
« Reply #14 on: February 27, 2018, 04:39:40 PM »
If you're going to run it off-road won't you need a lock for that diff?

AS
Quidquid latine dictum sit altum sonatur

Offline Perry

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Re: Scratch built giant rc car
« Reply #15 on: February 27, 2018, 04:40:20 PM »
Wow what a project! I'm following  :whoohoo:

Offline KB

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Re: Scratch built giant rc car
« Reply #16 on: February 27, 2018, 07:43:34 PM »
Thanks for the encouragement.

Mike yes it is a window motor and if that is not enough I have a wiper motor. And yes the servo is there for positional feedback. It has been gutted and is essentially just a pot with a servo case for mounting.
I am electronically illiterate so I was thrilled to find this H-Bridge which is pretty much plug and play. "Servo Thor-15" at the bottom of this page; https://www.model-truck.ch/cti-elektronik-inkl-neuheiten/cti-fahrregler-mit-neuheiten/

Quote
If you're going to run it off-road won't you need a lock for that diff?

Allen, I hope not... If it starts unloading too much I can try packing it with sticky grease?

Cheers Perry,

KB


Offline Vixen

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Re: Scratch built giant rc car
« Reply #17 on: February 27, 2018, 07:57:10 PM »
Hello KevinB

Thanks for getting back.

I also made a giant servo for one of my tracked vehicles (a 1/6 scale tank) using a window winder motor slaved to a feedback pot in a servo housing. I also used the 'Servo Thor-15' amplifier. The first one smoked itself within minutes and I have a tad too much dead band on the second one I bought. The idea of maybe having to buy a third one if anything goes wrong is holding me back from experimenting with the electronics to fine tune the dead band. I was hoping you might have discovered an alternative manufacturer.

Mike
It is the journey that matters, not the destination

Offline KB

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Re: Scratch built giant rc car
« Reply #18 on: February 27, 2018, 08:25:32 PM »
Mike,

Hmm, now I am worried. I bought three. The first one I set up, was fine after some tinkering. I took it apart and some time later somebody asked how I wired it up so I put it back together and smoked it right away. I assumed I shorted the power or something. I'll fuse the power lead in the future.

There is a discussion here where someone mentions 7 points of rotation instead of 64. May be the dead spot you refer to? Love those giant RC tanks. Let's see it.

https://translate.google.ca/translate?sl=auto&tl=en&js=y&prev=_t&hl=en&ie=UTF-8&u=http%3A%2F%2Fwww.rc-baustelle.de%2Fthread.php%3Fthreadid%3D5848&edit-text=

Offline Art K

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Re: Scratch built giant rc car
« Reply #19 on: February 27, 2018, 09:12:01 PM »
Kevin,
As everyone else has said already that's way to cool. I have to admit recognizing that as a Honda 50 motor.
Art
« Last Edit: March 20, 2018, 03:14:21 PM by Art K »
"The beautiful thing about learning is that no one can take it away from you" B.B. King

Offline Vixen

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Re: Scratch built giant rc car
« Reply #20 on: February 27, 2018, 09:50:43 PM »
Hi Kevin,
I think the Servo-Thor-15 is a fragile design. There seems to be no reverse polarity protection or short circuit protection. I would advise well-made non-reversible connectors to avoid the unprotected conditions. You can understand why I was looking for an alternative. I am not sure a fuse will help, I expect the module to die before the fuse goes. Iwill check out the link you sent tomorrow.

If you wish to see my 1/6 scale StuG 111 self propelled gun go to
If you poke around the 'more' button, there are some other of my videos.

Mike
« Last Edit: February 27, 2018, 10:01:57 PM by Vixen »
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Offline KB

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Re: Scratch built giant rc car
« Reply #21 on: February 28, 2018, 01:19:11 AM »
Thanks Art!

Mike, outstanding. The V-8 alone is an amazing project. Recoil, smoke and everything.

I'll try a Deans connector or something of the like. It sure seams light for 18 amps. I was planning on mounting it to a fan cooled heat-sink.
There are arduino options but I prefer building to research...

http://www.instructables.com/id/Wiper-Motor-and-Arduino-Mega-Servo/

https://www.pololu.com/product/1392

Edit : They also say it is supposed to be short circuit and temp. protected;

https://translate.google.ca/translate?sl=auto&tl=en&js=y&prev=_t&hl=en&ie=UTF-8&u=https%3A%2F%2Fwww.model-truck.ch%2Fapp%2Fdownload%2F5587893211%2FAnleitung-SERVO%2BTHOR15%2BCH%2BServoelektronik.pdf%3Ft%3D1465139799&edit-text=
« Last Edit: February 28, 2018, 01:40:51 AM by KB »

Offline KB

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Re: Scratch built giant rc car
« Reply #22 on: March 20, 2018, 03:49:55 AM »
Spring is here and the jobs are piling up but we got a little time in.







Offline bent

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Re: Scratch built giant rc car
« Reply #23 on: March 20, 2018, 05:20:57 PM »
Dang!  Very cool, Kevin!

Offline KB

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Re: Scratch built giant rc car
« Reply #24 on: March 30, 2018, 01:17:52 AM »
Thanks Bent!

I had a little time to make this chain tensioner;


Offline Admiral_dk

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Re: Scratch built giant rc car
« Reply #25 on: March 30, 2018, 06:57:17 PM »
A good chain tensioner is a great thing to prevent problems and bad temper after the fact  :ThumbsUp:

Offline steamer

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Re: Scratch built giant rc car
« Reply #26 on: March 30, 2018, 10:40:32 PM »
Great work!     Consider allowing for adjustment of roll center   antisquat and kick up as well as provision to move the shock mounting points.     Will make set up at the track very easy.    What are you using for diff oils?
« Last Edit: March 30, 2018, 11:15:36 PM by steamer »
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Offline KB

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Re: Scratch built giant rc car
« Reply #27 on: May 02, 2018, 03:53:33 AM »
A_dk, indeed!

Thanks Dave,

The way I made the top caps of the shocks didn't allow me to have room for additional mounting points.
I should have used rod-ends on both ends
The front lowers have a few options.

I just have high pressure grease in the diff for now.

The shocks are 11/2" bore by 3" stroke, what do you think I should try as a starting point for piston holes? Do you have any recommendations for cheap shock oil?

I don't have a lot of time these days but I am starting to look at the drive train;





Offline KB

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Re: Scratch built giant rc car
« Reply #28 on: May 05, 2018, 01:47:47 AM »
Quote
I was hoping you might have discovered an alternative manufacturer.

Mike

Mike, I have figured out a higher amperage set-up;



Offline KB

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Re: Scratch built giant rc car
« Reply #29 on: May 05, 2018, 02:04:22 AM »

Offline KB

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Re: Scratch built giant rc car
« Reply #30 on: November 23, 2018, 07:09:12 PM »

Got a little more time in...





Offline KB

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Re: Scratch built giant rc car
« Reply #31 on: November 23, 2018, 07:10:14 PM »

I had a little time to play with the steering. Not sure what is going on here. The servo, by itself, is smooth acting but when it is connected to the steering linkage, it gets super glitchy, some kind of resonance. There is very little play. It quiets down a bit under load.

 I'll try a different motor....


 


Offline Vixen

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Re: Scratch built giant rc car
« Reply #32 on: November 23, 2018, 08:46:13 PM »
Looked smoother and less twitchy in your earlier 05 May posting, so it can be done.

Mike.
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Offline KB

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Re: Scratch built giant rc car
« Reply #33 on: November 23, 2018, 09:19:17 PM »
Thanks for the encouragement.

By itself it is smooth even with a load applied and yanking on it. Only when it is connected to the rest of the linkage, it is twitchy?
Im going to try a longer servo horn on the feedback servo. Also have a wiper motor to try.

Offline Vixen

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Re: Scratch built giant rc car
« Reply #34 on: November 23, 2018, 09:25:56 PM »
If it is smooth by itself and only becomes twitchy when you add the weight and inertia of the road wheels, then it sounds like a steering damper cylinder may help.

As you say, changing the servo horn length/ratio may also help.

Mike
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Offline crueby

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Re: Scratch built giant rc car
« Reply #35 on: November 23, 2018, 09:44:07 PM »
Do you have capacitors on the motor, like you would on a drive motor?

Offline Noitoen

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Re: Scratch built giant rc car
« Reply #36 on: November 23, 2018, 10:05:12 PM »
You could move the feedback potenciometer to the stearing arm itself. This could minimise the "hunting " effect.

Offline KB

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Re: Scratch built giant rc car
« Reply #37 on: November 24, 2018, 12:55:44 AM »
Mike, here is the damper/servo saver set-up. There is no resistance and little weight so I don't know, weird. I'll see if the ratio smooths it out but by itself I can wiggle the servo horn with no effect.





Crueby, this is the h-bridge; I read somewhere that the capacitors were not the best quality. I no nothing of electronics.



Noitoen, good call, I'll try.

Cheers,

KB

Online Jasonb

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Re: Scratch built giant rc car
« Reply #38 on: November 24, 2018, 08:44:20 AM »
Can you bypass the radio and try moving the servo directly just in case all those metal ball joints are interfering. Also try it with just the link to the servo saver, then add one steering rod and then the other to trace down where it starts to happen.

Also what is the red lead clipped to the toolmakers clamp doing?

Offline MJM460

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Re: Scratch built giant rc car
« Reply #39 on: November 24, 2018, 10:30:35 AM »
Hi KB, you mentioned earlier that you thought the issue might be a resonance issue.  Hard to tell from the video, but if so, it is is about the natural frequency of the steering motion.  That is determined by the moment of inertia of the wheels (about the vertical steering axis) and the springs in that servo saver.  Applying the load by hand does not replicate the natural frequency, so tends to support your view that it is a resonance.

It is easily checked by making a temporary solid replacement for the servo saver unit which will drastically change the natural frequency, and probably eliminate the problem, so confirming whether a resonance is the issue.  Alternatively it will make no difference in which case you need to look elsewhere, possibly in the servo characteristic.  But I imagine you need the servo saver on a real world track.

In that case, to change the natural frequency, you need to change either that moment of inertia of the wheels, which is not very practical, or to experiment with the stiffness of those springs.  You may need to test the system with each of the tyres you intend to use if they are significantly different in weight.

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Offline steamer

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Re: Scratch built giant rc car
« Reply #40 on: November 24, 2018, 12:59:55 PM »
Is there any control over the control loop?    Is it a PID control?     Perhaps backing off on the Proportional gain will help?

AS the Servo is a wiper motor, and pretty cheap, I might just take the servo saver out all together for the moment and only put it in if needed.

Most servo savers are of this design by the way.  The design is very damped, and quite stiff, and is a very common design amoungst most manufacturers.

Dave
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Offline steamer

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Re: Scratch built giant rc car
« Reply #41 on: November 24, 2018, 01:18:06 PM »
A_dk, indeed!

Thanks Dave,

The way I made the top caps of the shocks didn't allow me to have room for additional mounting points.
I should have used rod-ends on both ends
The front lowers have a few options.

I just have high pressure grease in the diff for now.

The shocks are 11/2" bore by 3" stroke, what do you think I should try as a starting point for piston holes? Do you have any recommendations for cheap shock oil?

I don't have a lot of time these days but I am starting to look at the drive train;






You should check out my friend Matt Olson's web page   MOD speed shop
 
https://modspeedshop.com/

His 1/8 and 1/5 scale bypass shocks are the technology you should be looking at.

His 1/5 scale shocks are 32mm bore


Dave




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Offline steamer

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Re: Scratch built giant rc car
« Reply #42 on: November 24, 2018, 01:22:40 PM »

William and Matt throwing down at the King of the Dirt after race grudge match....  1/10 vs 1/5 scale, both with bypass pistons


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Offline steamer

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Re: Scratch built giant rc car
« Reply #43 on: November 24, 2018, 01:27:47 PM »
As far as cheap shock oil, I would look at most hobby shops or online shops.    TLR and Team Associated will have the least expensive oils.

You really want a silicone based oil, and I would shoot for piston port sizes that get you in the TLR  "35 weight" range, as you will then be in the middle of their product range for oils

That will give you the most adjustability for a wide range of surface conditions.

I would start at 10 hole x 1.0 mm    You can then go up from there easily.

Dave
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Offline KB

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Re: Scratch built giant rc car
« Reply #44 on: November 24, 2018, 06:14:07 PM »
Thanks for the advice.

Jason, everything is quite free to move, but I'll try to power the motor directly, good idea.
The red lead was an attempt at grounding everything.

MJM460, thanks, the springs are quite stiff and shouldn't be a factor in a free state but it is certainly worth a try. I'll just swap out the spring cylinder for a threaded rod.

Dave, lots of good info there, thanks. The gutted servo provides the feedback. I got this radio a while ago, so that I would be able to set the endpoints. I thought that the proportional gain might make a difference, but I only just started playing with it and don't really know what I am doing.. It also has adjustable frame rate speed. The old servo is analog, so I think I am supposed to set it to the slowest?

https://www.rccaraction.com/radiopost-ts401-2-4ghz-color-lcd-radio/

I have that cam style servo saver on my T-Maxx, I considered it but got lazy.
I'll start with 10x1mm thanks, looking at those pistons the is a lot less through surface are than I would have thought.

Cheers!

Offline steamer

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Re: Scratch built giant rc car
« Reply #45 on: November 24, 2018, 06:55:03 PM »
I know that will be far too small  ( 10 holes at 1mm diameter) so just keep opening the holes up a little at a time until they work on a fairly smooth surface with 35 wt.   Then you can go up and down with oil viscosity as a tuning aid
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Offline AlexS

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Re: Scratch built giant rc car
« Reply #46 on: November 25, 2018, 05:47:46 PM »
Hi KB. Interesting construction project!
As others indicate, the vibration in the steering could be remedied by using a damper or changing springs or weight of the wheels.

It is difficult to determine whether this fully follows the natural frequency.
I saw this passing by and thought, maybe I can help somehow to draw up a small model. In order to map out the natural frequency in a simplified manner of the control device. And on the basis of this change parameters such as spring strength and or application of a damper.
This might create some insight.

As an example I have made a model in which a certain mass and corresponding radius get a corner rotation. This mass is connected to a spring (2nd model + damper) over a certain distance from the center of the mass.
This model gives an outline of how the rotation of the mass would take place with the use of only a spring or with a damper.

I find it interesting to look at this. For this I do need the masses and dimensions of the components of the steering system. And any spring constant of the mounted spring.
Let me know if this seems like something to you!

Offline Vixen

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Re: Scratch built giant rc car
« Reply #47 on: November 25, 2018, 06:40:40 PM »
If it is smooth by itself and only becomes twitchy when you add the weight and inertia of the road wheels, then it sounds like a steering damper cylinder may help.


By steering damper cylinder, I meant a hydraulic shock absorber, similar to a suspension shock absorber, between the steering arm and the chassis. I believe this would kill the inertia and overshoot and system resonance from the front road wheels. The steering servo saver is there for an entirely different purpose.

Mike
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Offline steamer

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Re: Scratch built giant rc car
« Reply #48 on: November 25, 2018, 06:47:53 PM »
Hi KB. Interesting construction project!
As others indicate, the vibration in the steering could be remedied by using a damper or changing springs or weight of the wheels.

It is difficult to determine whether this fully follows the natural frequency.
I saw this passing by and thought, maybe I can help somehow to draw up a small model. In order to map out the natural frequency in a simplified manner of the control device. And on the basis of this change parameters such as spring strength and or application of a damper.
This might create some insight.

As an example I have made a model in which a certain mass and corresponding radius get a corner rotation. This mass is connected to a spring (2nd model + damper) over a certain distance from the center of the mass.
This model gives an outline of how the rotation of the mass would take place with the use of only a spring or with a damper.

I find it interesting to look at this. For this I do need the masses and dimensions of the components of the steering system. And any spring constant of the mounted spring.
Let me know if this seems like something to you!

Also you can check out a RC vehicle dynamics analysis program on the market called "RC Crew Chief"   It's quite detailed and gives good predictions on handling changes.

Dave
 
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Offline AlexS

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Re: Scratch built giant rc car
« Reply #49 on: November 25, 2018, 07:02:59 PM »
Dave, looks like an interesting site and analysis program.

Offline KB

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Re: Scratch built giant rc car
« Reply #50 on: November 25, 2018, 09:40:26 PM »
Alex, thank you for your time and insight. Fascinating. I do have most of this modelled in CAD which can give me mass, but something like spring constant is beyond me. I appreciate your time. Let me try some simple things first.

Mike, thanks, I see what you mean. Last night I made a longer servo arm which didn't seem to help much but I turned up the frame rate on the radio system and that seemed to help some as well as a load on the steering knuckle. But I need to be 100% throwing this kind of weight around.

Dave, thanks I'll check that out.
This is the radio I have. http://www.competitionx.com/pdf/radio-equipment/radiopost-ts-401-manual.pdf
I have just started playing with it. What can I adjust to make the steering less sensitive at centre? Negative expo?
I bought this radio a while ago so that I could set the endpoints and have an extra channel for a kill switch.
Also do you know if something like the super bee failsafe would work on a four stroke?

Thanks all!

Offline steamer

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Re: Scratch built giant rc car
« Reply #51 on: November 25, 2018, 09:43:21 PM »
The link comes back forbiden.  Cant open it
"Mister M'Andrew, don't you think steam spoils romance at sea?"
Damned ijjit!

Offline KB

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Re: Scratch built giant rc car
« Reply #52 on: November 25, 2018, 11:08:13 PM »

Offline KB

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Re: Scratch built giant rc car
« Reply #53 on: December 02, 2018, 06:29:29 PM »
I ended up switching to a wiper motor and it still behaved strangely. I indexed the feedback servo horn away from what I thought was centre and it smartened right up! I think it was bouncing around in a dead zone in the pot..?



Offline Vixen

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Re: Scratch built giant rc car
« Reply #54 on: December 02, 2018, 09:36:39 PM »
Looks good.  :ThumbsUp: :ThumbsUp:

What happens when you add the weight and inertial of the two road wheels? Is it still nice and smooth, or does it overshoot?

Mike
It is the journey that matters, not the destination

Offline Florian Eberhard

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Re: Scratch built giant rc car
« Reply #55 on: December 02, 2018, 10:06:48 PM »
Hi Kevin

Looking very good! Just one thought - I think your servo is maybe a bit small for the size of your car.
Do you know about the large size servos that are used in 1/5 scale rc cars?

Florian

Offline KB

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Re: Scratch built giant rc car
« Reply #56 on: December 03, 2018, 11:24:21 PM »
Thanks Mike, I haven't tried it with wheels on. The frame jig needs to be lifted for that, (I did build a rotisserie attachment for when it comes time to weld it all out.) But it seems pretty solid.

Thanks Florian. When I started this adventure high power servos were quite expensive, they have come down in price. A quarter scale, double servo set-up might work but I would call this just about half scale. I also like the DIY component of this route.

I put a fish scale on the end of the axle, pulling more than I could hold! Could crush a finger for sure.


Offline steamer

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Re: Scratch built giant rc car
« Reply #57 on: December 04, 2018, 12:45:19 AM »
Seems to be working now.   Was it a tuning issue or was the servo too small?

Dave
"Mister M'Andrew, don't you think steam spoils romance at sea?"
Damned ijjit!

Offline AlexS

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Re: Scratch built giant rc car
« Reply #58 on: December 04, 2018, 10:20:58 PM »
Great work! If wheels add inertia and friction has also come with some overshoot, you should also try an old trunk damper.  Mount this on the steering arm. Maybe make a long steering arm with multiply holes, so you could change the radius to attache the damper so also the speed of damper movement. So you could change this to try not to much damping or over damping.
No thanks for the model. I had it already. I though it could be possible to 'copy' the steering movement shown in your video. Just to add an extra damper in the model and tune this to get the same sway movement. And then modify the second damper to get it right.
If you want to try this. I am open to try this. If you want to share your 3D modeling.
Alex

Offline Florian Eberhard

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Re: Scratch built giant rc car
« Reply #59 on: December 05, 2018, 07:08:29 PM »
Hey Kevin

Yes, the torque of your servo seems to be quite enough. I rather thought about the gears of the servo than its power - in case you have an impact. But maybe I am just a bit too cautious..  ;)

Florian

Offline KB

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Re: Scratch built giant rc car
« Reply #60 on: December 05, 2018, 08:20:25 PM »
Dave, I am not really sure. I think the feedback servo was causing some eratic signals.

Alex, thanks. There is a spring loaded damper similar to what you describe. It seems okay for now and my time is limited but I would be happy to share the model for further insight and analysis.

Florian, yes I see what youy mean. The worm wheel is plastic and as the rotation is not full, if a few teeth are broken, I could index it to a fresh set. There is a spring loaded piston damper built, in the hope of absorbing shock loads. The shock also has to be transferred through several pivot points before directly bearing on the worm. I don't know if this will stand up but If I ever get to the point of a test run, I will be testing everything until failure.

The testing facility;


Offline KB

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Re: Scratch built giant rc car
« Reply #61 on: December 17, 2018, 03:19:12 AM »
One of the test pilots checking out the roll cage.


Offline Kim

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Re: Scratch built giant rc car
« Reply #62 on: December 17, 2018, 04:58:47 AM »
Now THAT's a great picture!    ;D
Kim

Offline Chester

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Re: Scratch built giant rc car
« Reply #63 on: December 17, 2018, 07:59:14 AM »
Seems like the young fellow has it figured, I know if I get my tongue 👅 held just right, my measurements usually fall just where I need them!

Offline KB

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Re: Scratch built giant rc car
« Reply #64 on: December 26, 2018, 04:40:45 AM »
Thanks Kim, Chester, you know it, if he doesn't have it just right it never works. #1 has been working on his welds.





cut, cope, tac continue....



Merry Christmas.


Offline AlexS

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Re: Scratch built giant rc car
« Reply #65 on: January 05, 2019, 11:54:27 AM »
You are never too young to start learning welding.

And great progression!

Offline KB

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Re: Scratch built giant rc car
« Reply #66 on: January 11, 2019, 12:47:14 AM »
Thanks Alex!

I need to learn too! As you can see;

Fuel cell;















We're running out of room! Still need to build the throttle/brake/servo, mount the battery and house the electronics.

.

Offline AlexS

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Re: Scratch built giant rc car
« Reply #67 on: February 20, 2019, 09:46:35 PM »
Nice aluminium welding job.

I've tried it with some remaining staff material. But I came up with the idea of ​​melting aluminum for castings rather than welding a bit. Any hinds or tips? I did used an standard equipment for tig welding of stainless steel.

Offline bent

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Re: Scratch built giant rc car
« Reply #68 on: February 21, 2019, 08:11:58 PM »
Stainless likes dc tig, you need AC tig for alumin(i)um.

Offline KB

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Re: Scratch built giant rc car
« Reply #69 on: February 23, 2019, 07:58:30 PM »
Thanks Alex, took me a few tries to chase down all of the leaks. Like Bent said AC for aluminum.

Got the chassis up in the rotisserie to weld it out.










Offline ddmckee54

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Re: Scratch built giant rc car
« Reply #70 on: March 06, 2019, 09:59:06 PM »
KB:

Any idea what the all up weight of that thing is by now?

Don

Offline KB

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Re: Scratch built giant rc car
« Reply #71 on: March 13, 2019, 09:50:46 PM »
Hi Don, I am guessing at least 150 lbs, when all is said and done.
Going to need an insurance policy!


Offline crueby

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Re: Scratch built giant rc car
« Reply #72 on: March 13, 2019, 10:16:00 PM »
Wow! Going to need a ramp down from the back of your car to drive it. Hmmm.... open the sunroof and jump it up the ramp?!
Awesome work!