Poor Man’s Dyno or Motor Checker
http://www.vimeo.com/3160587Poor Man’s Dyno or Motor Checker Video
I wanted to compare some motors, and wanted a simple way of reading RPM. So I needed an RPM counter of some sort. I thought about making one, but I quickly came across some on ebay.
I ordered one up, and it’s quite a bit bigger than I expected it to be, but that’s not a big deal.
It works very simply, you stick some reflective tape to whatever is rotating, and shine the laser on it. The reflective part needs to be less area than the non-reflective part. It then just counts the reflections and displays the RPM.
Brilliantly simple. Sure, it doesn’t check anything else, no torque measurements, or current measurements etc, but for a quick and dirty comparison it’s great.
It is of course important when checking motors to ensure that the voltage is similar on all of them. So use a fully charged race pack, and test them all at the same time, one after another.
I could even go so far as to test them under load, such as fitting them into a car and using the drivetrain as a load, as long as it’s the same conditions for each motor then it should be consistent and useful.
Written by simon.
Connectors for Fans etc. on Radio Controlled Cars
I picked up some of the small 2mm ‘Corally’ type banana connectors, off of ebay [search for: 2mm gold connector], these are ideal for use connecting fans, UBECs, LiPo cut-offs, etc.
http://www.vimeo.com/2991381In my e-savage I had two fans and a UBEC I wanted to connect direct to the battery voltage. I connect two wires, one to each of the +ve and -ve on the Deans battery connectors, and run them to where I want the sockets of for the accessories.
Then, I soldered three of the 2mm sockets in a small triangle, and onto one of the power wires. So 6 2mm sockets in total, 3 +ve, 3 -ve. Heatshrink around each triangle of three, gives a nice neat 3-way socket.
On each fan/ubec I have a 2mm plug on the power wires, heatshrink them again and plug them into the socket.
It’s important that there is no bare connector showing, especially as the +ve and -ve are often positioned next to each other.
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.
RPM Bumpers for HPI E-Savage
The VERY FIRST TIME I used my E-Savage I broke the front bumper, I tried superglue to no avail.
I discovered that RPM had produced some bumpers that were claimed to be unbreakable, and they had shiny nudge bars too. I ordered some up and they weren’t cheap at $17.95 each, cost me £20 shipped…
They arrived, and look great, they’re solid, well made, the usual good RPM product.
One nice feature is that it moves the switch from the rather exposed position on the standard bumper up onto a nicer position on the rear shock mount.
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.
