RC India

Hi people

So i decide to get me a crawler and i wanted to start cheap, and i wanted the thing modular. Maybe i will go for ali stuff later i get hooked on to it.  

I get it out of the box and it crawls very nicely indeed, but i am a tinkerer... a wrench monkey so here is the evolution of my car...

Stage 1
Stock
(http://i877.photobucket.com/albums/ab336/abhisheknakhwa/1-2.jpg)
I forgot to photograph the thing so i am using a stock photo.

I heard the drive train and the servos are not the most durable. So i went easy on them.


Stage 2
Metal gears for the front drive train. Sorry i don't have photos of this but the logic was that i changed the front plastic gears to hardened metal before they went crunch. This way i have a spare set when the rear drive-train gears die.


Stage 3
Bent rear links.
(http://i877.photobucket.com/albums/ab336/abhisheknakhwa/DSC_5606.jpg)
(http://i877.photobucket.com/albums/ab336/abhisheknakhwa/DSC_5611.jpg)

Scratched my head a bit for this. I did not want to grab them in a vise and yank with pliers. That would leave a kink on them. So i made me a tool. Basically a stupidly simple arrangement of 3 3/4 inch pipes welded / bolted together. Got a chance to brush up my welding skills as well. The thing did not work as i thought so i used a C clamp to put accurate pressure. The result was pleasing.

(http://i877.photobucket.com/albums/ab336/abhisheknakhwa/DSC_5612.jpg)

This increased the ground clearance by a LOT! Can now go over things it used to high-center on.

(http://i877.photobucket.com/albums/ab336/abhisheknakhwa/DSC_5609.jpg)


Stage 4
Bent front links and Lowered Body

(http://i877.photobucket.com/albums/ab336/abhisheknakhwa/DSC_5615.jpg)
(http://i877.photobucket.com/albums/ab336/abhisheknakhwa/DSC_5614.jpg)

The lowered body makes it look much better. Some benefits for the CG too. Had to trim quite a bit of bodywork to make it fit and not interfere withe the wheels at full articulation. Had to chop a bit from the body posts to get it to fit properly.


Stage 5
Front servo

(http://i877.photobucket.com/albums/ab336/abhisheknakhwa/DSC_5618.jpg)

Dropped in at THS last evening and picked up the MG 10.2 kg servo. Its way better than stock 6kg Lansu servo. I got only one because i may do a rear steering lock-out also i now have a spare stock servo if the rear one dies. This servo has a larger throw so i get more steering angle... Great! but the front suspension mount hits the tyre... not so great. So i go back to scratching my head...

Options tried:
1. Relocating the suspension mount: Makes the front of the car stand on stilts... no good for CG.
2. Relocate the suspension from both ends: Makes the front go too low... no good for ground clearance.
3. Droop setup at the front: Makes it a floppy piece of s#it.
4. Reversed front links + relocate the suspension: Works!

(http://i877.photobucket.com/albums/ab336/abhisheknakhwa/DSC_5616.jpg)
This makes the front softer than the rear and it seems to work a bit better this way... win win!

(http://i877.photobucket.com/albums/ab336/abhisheknakhwa/DSC_5617.jpg)
Perfect clearance for everything.

Stage 6
Power connectors

(http://i877.photobucket.com/albums/ab336/abhisheknakhwa/DSC_5619.jpg)
Go those, cables and the heat shrink from THS. Don't know what type they are called and i forgot to ask. Felt better than Deans for some reason but it might just be my feeling. Soldered them all last night. Much better than the stock flimsy things.

That is it for now.

Future upgrades...
Will definitely be doing a wheel weight mod. I don't want to pour too much money into this, i have my RD350 cafe racer (and my wife too) for that. So it will be a homemade mod for that.

Had a tense moment last night; The rear steering servo started glitching and steering on its own when i throttled up. Front was fine. Connected the old servo at the front and that started glitching again. Did some digging on the net and learn that maybe my battery was going flat. Today morning i charge it and its all fine now. Thought for a moment i would have to go for a new receiver.

Will try to keep you folks updated
cheers

Abhishek

Sweet job man. I finally found someone who can use this video...
http://www.youtube.com/watch?feature=player_embedded&v=E95xT4NN98Y

Thats a really good and easily doable method. the only possible problem is the drill going in slanted and breaking off from one side. but its solvable.

thanks

If you have a jig like he has, it shouldn't be much of a problem.

Ya, the jig is critical. i think i will make one. i wish i had a lathe. wont be too hard without one... the outside doesn't need to be round and maybe i will integrate a way to clamp the link to it while working.
The thing is the links are ok for now. eventually i am going to do a new chassis, and that will need all this.

For now i am scratching my head for the wheel weights.

Lead weights? You can ask places where they balance tires. They should have some. I think golfers add lead weights to their clubs as well. You can try a place that sells golfing equipment.

Golf! never thought of that one.
The issue is that i read on the net that people usually add about 7 to 9 oz to each front wheel. thats at least 200 gms. even if i can manage to fit 6 20 gm weights in each wheel, i am only running with 120 gms per wheel.
Its a good start though.

was thinking of turning a steel disc: 48mm OD, 20mm ID, 10mm Thick. but that would only give me approx 120 gms. Your lead weight idea is much better.
Thanks.

You're welcome. I believe lots of folks use lead weights. RC specific ones are overpriced, IMO.

Stage 7
Wheel Weights

(http://i877.photobucket.com/albums/ab336/abhisheknakhwa/DSC_5621.jpg)

So went out and bought some 'sticker weights' as they seem to be called from a nearby tyre shop. Bought 3 strips of 60 gms each.


Now to figure out how to get them on the wheels. I did not want to get them inside the tyre because it will compress the foam and make it stiffer.
so this is what i did:

(http://i877.photobucket.com/albums/ab336/abhisheknakhwa/DSC_5626.jpg)

But that was a no-go. interfered with the knuckles, so option 2 was to fit the weights inside the tyre. thankfully the foam is so soft, it doesn't matter if it gets compressed a bit. Also the wheel weights fit perfectly:

(http://i877.photobucket.com/albums/ab336/abhisheknakhwa/DSC_5629.jpg)

I got 80 gms in each front wheel. That's less than i thought i would use but i can always add more later.
It crawls a bit better but not a very big difference. I am a bit reluctant to add weight at the back because its my 'weak' (stock) axle. I suppose i need to do something about that. Anyway, at least it definitely is not worse.

I am planning to go to the rc meet at Baner this Sunday. not entirely sure what kind of terrain i will find there but will try to chat some rc folks up.

cheers

That looks like a great build! Have only seen a handful of crawlers in India. Very few build crawl builds on here, as compared to regular builds. But that was expected, I guess, as lots of us like speed :)

cant blame you for that!
i have my bike for my occasional fix. ;-)

I like crawling because i find it very technical. a brain thing more than anything else.

Stage 8
Relocating the suspension on the axle.

It was on the links and that was fine for straight links. the links started flopping around too much after i bent it. so found a donor bit of metal and made a bracket like i saw somewhere else on the net. Made it larger than necessary but i can trim it down.

(http://i877.photobucket.com/albums/ab336/abhisheknakhwa/DSC_0151.jpg)

(http://i877.photobucket.com/albums/ab336/abhisheknakhwa/DSC_0152.jpg)

(http://i877.photobucket.com/albums/ab336/abhisheknakhwa/DSC_0154.jpg)

(http://i877.photobucket.com/albums/ab336/abhisheknakhwa/DSC_0163.jpg)



Made them for both axles and had to bend them to got them to fit.
Improved the predictability of handling quite a bit.


Stage 9
More center clearance and tuning.

The bent links worked good but there was scope for improvement. so bent the rear links more and bent the front links in another plane to clear the motor better.

(http://i877.photobucket.com/albums/ab336/abhisheknakhwa/DSC_0158.jpg)


Stage 10
Clocked axles corrected wheelbase.

Tried a steering pin castor. needed to relocate the upper links for that and there were no holes on the chassis plates for that. so made some.

(http://i877.photobucket.com/albums/ab336/abhisheknakhwa/DSC_0156.jpg)

It was all good but the rear motor hit the obstacle in some cases and the wheelbase was less than 12 inches. Competition rules allow 12.5". so went out and got long nuts, long grub screws of various lengths to extend the wheelbase.

(http://i877.photobucket.com/albums/ab336/abhisheknakhwa/DSC_5636.jpg)

could really tune the chassis using those nuts. used then to extend the rear suspensions too. now the whole chassis and body sit bar ahead and that is great for CG.

(http://i877.photobucket.com/albums/ab336/abhisheknakhwa/DSC_5631.jpg)

Present iteration:

(http://i877.photobucket.com/albums/ab336/abhisheknakhwa/DSC_5630.jpg)

(http://i877.photobucket.com/albums/ab336/abhisheknakhwa/DSC_5639.jpg)

(http://i877.photobucket.com/albums/ab336/abhisheknakhwa/DSC_5638.jpg)

You can see the scratch marks on the body in the last pic: proof its being used as intended.

Next stage, custom aluminum body-less chassis. but that may take a while. need to find time to do it up on cad, then get it laser cut.

Till then, cheers!