DIY crawler for me & my kid

[trewq]

Hello chaps,

I've set my mind on building a two seater electric "crawler-buggy" for me & my little one.
Well, not quite a full capable crawler as I'd start with RWD for the sake of simplicity, but it might end up being a 4WD at some later stage. I was thinking of making a 3D model which would have front drive and just omitting that in the build...

Well, to start of in self motivating my "easy to lose interest ass" I've already purchased Turing Rotomax 50cc motor which should be good enough to move the car. Matched to it is 8S 200A ESC which is designed for 1:5 RC cars. I know it is only 8S but that should get us moving for the start. At the time this one was the biggest available ESC which was not designed for aviation and I've picked it up for the project.

And just in case you guys think that this will not be motivating enough, I've also picked up an ZX45 mill and C6128 turning machine. Well that should give the project a nice push and some motivation I reckon

As this is my first build from scratch and far off from a model kit that I used to build until now, I would ask for some suggestive help on sourcing some of the components.
In particular I'm looking for an open differential that would be big enough to handle 300kg of vehicle. If you know of anything that would do I'd really appreciate it.

Please feel free to comment, suggest and be constructive!
Cheers

[trewq]

Huh, I've got some time to post the picture of my machines that I'll be using in this hobby.

The plan for the mill will be to convert it to CNC at some point, but I'd reckon only after we make the buggy.


This one might also get few automated functions. Primarily depending on need for automated machining. There are no plans, but there are few ideas of that would be cool to have...

Cheers

[Noll11]

"only" 8S??? This is going to be great!

[twissted]

I would look at the Losi 5 diff gears with a cnc diff housing and case. Spendy but your project will need it.
Also look at the Losi LST design on the diff mounting. This will help you make it a 4x4 that is easy to work on and use the same parts.
What wheel base are you looking for and what Transmission are you planning on using?
Do you have a body style that your looking at or is it a custom cage that you plan on using?
I have built a custom one off 8s 4x4 SC truck using the Losi cage and a carbon fiber body. It is very fast and bends drivelines like crazy.
Good luck with your build.

[trewq]

Originally Posted by Noll11

"only" 8S??? This is going to be great!

Well, that will get us going, but ultimately we should look for something like 14S to use max potential of the motor. the only bottleneck right now is the ESC which is limited to 8S
It is still to early to think about that.

[trewq]

Originally Posted by twissted

I would look at the Losi 5 diff gears with a cnc diff housing and case. Spendy but your project will need it.
Also look at the Losi LST design on the diff mounting. This will help you make it a 4x4 that is easy to work on and use the same parts.
What wheel base are you looking for and what Transmission are you planning on using?
Do you have a body style that your looking at or is it a custom cage that you plan on using?
I have built a custom one off 8s 4x4 SC truck using the Losi cage and a carbon fiber body. It is very fast and bends drivelines like crazy.
Good luck with your build.

Hi Twissted, thanks for the pointer on the Losi 5 diff. I'll look in to it!

Well, the scale factor and the dimensions are not determined now. There are couple of factors which I'll need to account for. One of these factors would be the narrowest point in the only possible drive way to reach my shop. So I reckon I'll make a wooden frame first and see if I can pilot it in before we cut and weld anything.
Yes, the frame would be tubular to begin with.

My primary goals would be to have the buggy built to be able to carry two grown up persons or to be operated remotely via FPV link. Ant then we could add some tools to it

Would you like to share few photos of your rig?

Cheers

[twissted]

There is no point in showing you a diff that I have or of any RC that will do what you planning to carry people. You need to look at the diffs from a Subaru. In fact I would look into getting a hole car.
Also a ATV diff be a good choice. The ATV my cost you more though.

[Mike Flea]

I thought you were talking about a toy, you're talking about carrying 2 grownups, this should be in the 1:1 section.

[trewq]

Originally Posted by twissted

There is no point in showing you a diff that I have or of any RC that will do what you planning to carry people. You need to look at the diffs from a Subaru. In fact I would look into getting a hole car.
Also a ATV diff be a good choice. The ATV my cost you more though.

Hi,
Well I'm on a slightly smaller scale than the whole car.
Yes, the ATV's dif is something that I'm considering to use in the project, providing that I can source the axle at lower than rip off price.

The alternative to the rear (and front too) dif would be to use independent motor for each wheel. We'll see if the dif can be sourced or built first.

[trewq]

Originally Posted by Mike Flea

I thought you were talking about a toy, you're talking about carrying 2 grownups, this should be in the 1:1 section.

Well, depends how you look at it. I've got few 1:1 scale toys and I'd like a smaller scale one

I didn't post it in 1:1 section as the rig I plan on building will be a lot smaller than 1:1 vehicle, and it will have manual and RC controls.

[MountainStorm]

I would go with the hub motor idea. For the size you are thinking hub motors from mopeds would be ideal. Then the rest is just engineering a suspension that socks up to them and does what you want. Then the option to go to 4WD is easy.

[Mike Flea]

A couple years ago, Cabela's was selling a 4wd electric side by side golf cart with a motor on each wheel. You could go with something like that.

[trewq]

Originally Posted by MountainStorm

I would go with the hub motor idea. For the size you are thinking hub motors from mopeds would be ideal. Then the rest is just engineering a suspension that socks up to them and does what you want. Then the option to go to 4WD is easy.

There are positive and negative sides of hub motors. Technically they are desirable but when it comes to vehicle dynamics (if you wanna drive quick) then the hub motors are not that good.
I'll look at what is available and maybe we could make a comparison and test the urban talk... That would be cool. I'll look in to that.

Originally Posted by Mike Flea

A couple years ago, Cabela's was selling a 4wd electric side by side golf cart with a motor on each wheel. You could go with something like that.

I was also thinking of individual motors to eliminate the diff. The only thing that I'd like to add then is the possibility to couple the two sides together to form a "locked" diff which would be useful in some occasions. Something like a dog latch should not be that hard to machine... The only thing is, I need another motor, ESC and for all the extra power I'd need some more batteries too

[67mustang]

First post you start with "easy to lose interest". Aint gonna work out. Economics will be hard to overcome. If the little one is 10-13 go buy a geo tracker or suzuki samurai. Or a razr. Spend more time with your kid and less time building and engineering. Teach him to drive. If the little one is 8 or so....do a go kart build. You dont want your electric buggy getting spanked by a 2 seat 5hp murray.

[trewq]

Originally Posted by 67mustang

First post you start with "easy to lose interest". Aint gonna work out. Economics will be hard to overcome. If the little one is 10-13 go buy a geo tracker or suzuki samurai. Or a razr. Spend more time with your kid and less time building and engineering. Teach him to drive. If the little one is 8 or so....do a go kart build. You dont want your electric buggy getting spanked by a 2 seat 5hp murray.

Well you have nailed that one down in one line
Little one is 2. While playing with small carts I've noticed that he likes to drive or be driven around, and I simply had to start this project. I mean, I'd like it if my father did it while I was small kid. So, because I don't wanna scare him with otto engines I decided to pull the project from scratch and employ some BLDC motors to do the job.

Because of my work I am at home for only 5 months a year and while away I am planning to source the components needed for the build.

We'll see where we will finish with this project.
At present I am looking for complete rear axle assembly. From there we should start the design of the chassis and the suspension.

[trewq]

Well, I'm still far away from home, but eBay was good to me so I have bought a Hyperion EOS 0720i dual charger. This should keep the battery banks balanced and ready when we'll need to pull some current.

I have also bought 4 of LiFePo4 8,6Ah 4s cells.
I'll have these configured as 8s to begin with the project, and I hope we will find an ESC capable of working on 12S for later upgrades.

First rough sketches of the universal transmission have been made. There is lots of work to be put in to this before we get a functioning unit. I want to have independent motor drive for each wheel and to have an optional "diff" lock. Idea is to use that in very low gear to aid in climbing if that will ever be a problem.

I should be at home in a week time and then I'll have to hit the shop first, as there is a lot of unfinished business.

Cheers ;)

[spookyseven]

Some zero turn lawn mowers like the brand grasshopper have a shaft driven deck. You might be able to find a ring and pinion from one of these for a reasonable price and build the axle housing around it.

Edit: I didn't see you are looking to use a motor on each wheel instead of a straight axle.

[trewq]

Hello folks,
Thanks for guidelines!

Today I've visited few car scrapyards in the area. The catch of the day was 4 of shafts marked with number 7 on the following picture:


Not sure if it will be capable to act as a half shaft for the rear independent suspension, but it was worth $45US as it might be good for custom made prop shafts for a bit larger scale RC car. Tomorrow I'll have a look at some 55hp FIAT half shafts & hubs as these might be good source of raw material for the build.