Differential Drama Day
The diff on my Tamiya TRF415-msxx was a bit gritty today whilst racing, so I swapped it out after race 2 today. I put in a unknown 2nd hand diff I’d picked up, it felt okay, so went with it.
I cleaned and rebuilt the other diff, and it felt okay, so put it back in the car, but a run later and it was very notchy again, so the spare diff went back in Unfortunately, the spare diff managed to loosen itself, the nyloc nut was worn.
So I fiddled with the other diff some more, and got it smooth again, and back in it went.
Yes, you read all that correctly, I swapped diffs after every run. And in the last run, the diff failed again, notchy once more.
This evening once I got home, and messed about with all the diff parts I’ve got, and ended up chucking out 2 sets of ceramic balls (notchy, flat spots I guess), 3 pairs of plates (both sides pitted and used), 2 nyloc nuts.
I was left with a complete diff with ceramic balls and thrust, and a good enough nyloc, and it’s very nice now.
Spares didn’t quite go to a spare diff, I was a nyloc nut short of making up a spare steel ball / steel thrust diff.
I’ve ordered up some spares: a JAAD ceramic thrust, some EDIT ceramic balls, some Tamiya plates, some HPI nyloc nuts, some Tamiya sticky covers. ie Enough to make a spare ceramic diff and some other spares left over. That should get me through a good few months I think.
(And I won’t even talk about the front driveshafts… or the end result…)
Written by simon.
Futaba R603FS Receiver Repair
I was recommended Derek Bailey as someone who repairs Radio Controlled electronics, so decided to contact him to see if he could repair my broken Futaba R603FS 2.4gHZ receiver.
He was happy to have a look, so it’s on the way in a bubble wrap bag with contact details, and he’ll get back to me with a quote.
Fingers crossed.
A friend used him for an LRP Sphere repair and he only changed £15 or £20 or something.
There’s another chap who’s also been recommended, so it seems there’s hope when electronics break!
Written by simon.
HPI E-Savage 14 Cells How To – Add 2 cells!
A really easy way to go quicker, just add an extra couple of cells! The standard E-Savage is powered by 12 NiMh cells (14.4v), in 2 stick packs of 6.
I had lots of stick packs, which I wanted to keep standard, as I use them in other vehicles, and I have a balancing tray for stick packs. I wanted to run 14 cells in the E-Savage, to make 16.8v, so thought of ways to add two more.
HPI E-Savage 14 Cells How To from rcLazy on Vimeo.
The standard speed control can handle 14 cells okay, and it has two plugs on it, but effectively two of the wires are joined in a loop, so you end up with 12 cells in serial. I figured I could add two more cells to the chain to make 14.
The VERY IMPORTANT thing to consider though, is that the 2 extra cells must be of a higher capacity than the 2 x 6 cell stick pack. This is so that the 2 cells don’t dump first, when you’d hardly notice it wilth 12 cells still powering the car, thus damaging the cells.
So I had pairs of cells of 4200, 4500 and 4500, and I got hold of another 4600 pack, so split it into 3 x 2 cell packs.
Then, I made up an adaptor to plug the 2 cell pack in series with one of the 6 cell packs. It doesn’t really matter which side, as they are treated in series by the speed control.
Then I charged up all 3 packs separately, the six cell packs on the standard dual output GT charger, and the 2 cell pack on my other (Graupner) NiMh charger.
A simple bracket was made for the 2 cell pack to sit in, secured with a velcro strap.
UPDATE:
HPI E-Savage 14 Cells How To UPDATE from rcLazy on Vimeo.
After making this video, I went to the forest and tried the car, and I wacked the 2-cell bracket on a rock and ripped it clean off. I think it was perhaps too low, and that servo tape was not strong enough to hold it.
So I have to go back to the drawing board and modify my design. I figured I needed a 3 sided bracket, higher up out of the way, and fixed more firmly.
Written by simon.
Drying Waterlogged Tyres
Radio control car tyres usually have foams inside them, they are also superglued to the wheel, but they have holes on the inside of the wheel to allow the tyres to compress. When running in wet conditions dirt and water can get inside the tyre, soaking the foam, resulting in slowing the vehicle, and making the wheels out of balance.
Off-road racers routinely cut holes in the treads of the tyres, this allows the water a way out, as the vehicle moves, the centrifugal force makes the water leave the inside of the tyre via the holes in the tread.
Example Cut in Tyre
It’s easy to make these, you can do them neatly, with say a leather punch, but you need to do that before you glue the tyres on. If they are already glued on, you can make a small slit, say 6-8mm long in the tread. You can put several of these all the way around, perhaps 8 of them. You can use a small pair of scissors or a knife, be careful not to cut the foam below though.
When you run the vehicle, the water should be expelled as you are running, it’s a good idea to finish off the run with a quick blast with all wheels off the ground to get the maximum out.
If you want to wash the wheels, you can, and yes, the foam will fill up with water.
You can expell this by mounting an old axle in a cordless drill, put a pin in it, put the hex on, and bolt the wheel down onto the axle. Then, and this is very important indeed, put the wheel horizontally into a bucket, or the bath tub, and power up the drill, you’ll see an amazing amount of (usually dirty) water hitting the sides of the bucket very quickly indeed.
When you’ve finished put them somewhere warm to try and dry them out some more, they actually have a chance of drying now there is some way of the moisture getting out.
Written by simon.
Tamiya M03 Mini Build Tips
After weeks of my mini being a bit slow, I rebuilt it and I think I’ve cracked it. Went racing last night, and it seems a lot quicker, and I was a couple of laps up on people I was struggling against in the last couple of weeks.
It sounded a lot different, eager to accelerate, and it really sang at top speed, it sounded smooth and sweet.
One secret I didn’t tell you in the rebuild post, in case it didn’t work… I used GT85 on the bearings and on the gears, it dries to leave a PTFE coating, and I reckon that’s why it was sounding real nice.
It was handling a lot better too, more predictable, and stable, the suspension moving correctly helped, and I think the smooth ball diff helps it keep the speed in the corners.
Build tips:
- Make sure gearbox is free, give it a spin after every screw in the chassis, make sure it’s as free as possible.
- Take o-rings out of diff outputs, make sure gearbox spins at all points of suspension travel
- Build ball diff nicely, diff grease on big balls, graphite or anti-wear grease on thrust.
- GT85 all bearings and gears, no other grease on them
- Anti-wear grease on rebuildable UJs
- Clean your motor in coca-cola for 2 mins at 3v, wash with water, then motor spray, dry thoroughly. Oil both bronze bearings with very light oil.
- A drop of comms drops on each brush, make sure you let them soak in and power it up for a few seconds on the way to the line.
I just hope I’m now on the pace on Friday nights again, it’s been embarassing the last couple of weeks!
