LIPOS AND MINIS - A WEIGHTY PROBLEM

Lipos, love em or hate em, there's no avoiding the fact that they are here to stay. And chances are that within a few years NiMh batteries will be a thing of the past for most of us.
While we all love the ease of use and ruggedness of the Lipos, what they do to the handling of our Minis is another matter again. Yes there are a few people who just throw them in, and somehow their car still works. Chances are however that their car probably wasn't all that quick to begin with. For anyone seriously racing an M03 though, just throwing in a Lipo and leaving your car standard just aint gonna work.

So, how much weight then? Well, most Minis will come in at around the 1350-1400gm mark ready to race, depending on your radio gear. To be honest, that's not a bad figure to aim for. Our local comp has a minimum weight of 1330 for Minis now, mainly to actually HELP the people running Lipo, to force them to put weight in their cars so that have a half decent chance of handling properly without too many dramas.

But where you actually put this weight is just as important as how much. And here's where people seem to be getting it wrong. I've had a number of people bring cars to me that have gone from being easy to drive, to being absolute disasters with Lipos.
'But I've added weight?' they say
'Yes you have, but in the wrong places…'

What happens is that people try to 'fix' perceived handling problems by adding weight where they think the car needs it. Bad, bad move… Adding weight is not generally how you fix your handling problems. And a lot of people have tried to 'improve' their handling by adding weight in a specific area - also bad… A lot of people have ruined a previously good handling by thinking that they can make it better again by adding weight. Wrong, wrong, wrong…

It's actually quite simple when you think it through. If you have a sweet handling Mini in the first place, a large part of that handling comes from the way that the car is balanced. And that balance comes from the weight distribution. So…what we need to do is find out how the weight is distributed in a NiMh equipped Mini, and then transfer that same balance to the Lipo equipped car.

Put the car on the scales with a NiMh in, and check the weights. OK, now weigh the entire car with a Lipo in and work out how much extra you want/need to add. To be legal I need 1330 grams, but if possible I'd like to get my car back up to around 1400.
So all up I need to add 223 gms. All I need to do is make sure I add it in the right places so that the weight balance stays the same.

This car has a NiMh fitted and weighs in at 1361 gms

Whereas the Lipo car shown comes in at only 1138!

Full size race cars use a system called 'corner weighting' It's not rocket science, you just put a scale under each wheel, and the weight of the car is distributed over the 4 wheels. So you can see where the weight is at its highest. You can use this technique to really finely tune a car, but on a Mini it's just not necessary. In fact you can get away with 2 scales if you want. One for the front and one for the back will do just fine. We're interested in front to back weight distribution along the centreline of the car, so that's why 2 scales will also work fine. But, I had 4 scales so I used 4 - so there. Possibly I'm just showing off....

Here's a rare sight, an M03 being corner weighted!

This is the lead flashing, around 3kg worth.

With some pretty basic maths (it needs to be basic if I can do it!) you can work out the percentages front/rear. In the case of my car it works out at 58/42 with a front bias (hardly surprising) Most minis will be within 3-4% of these figures. So now we know what we have to do.

Now you can use lead weights to do this. Stick on wheel weights from your local tyre shop are good, or some people use lead shot from a gun (a little difficult to get it to stay put), or even lead sinkers from a fishing shop. We've used all of these but have settled on something called Lead Flashing (well that's what it's called in Australia anyway). Plumbers and roofing specialists use it to seal things. We bought a sheet of it at our local hardware store for $30 Aus. The sheet was 450mm square and weighed in at 3 kilos, so it's a hefty little bugger. And to offset the cost you can cut it Now we're going to add some more weight along the batterys centreline. Cut some more pieces of flashing, this time 25mm x 45. Fold these over 3 times as shown. These ones go on top of the battery holders hard up against the chassis. Once again these are along the centreline of the battery, and also concentrate the weight on the centreline of the chassis as well which is essential for good handling. These 2 weight are attached with double sided tape and weigh in around 20 gms each.into 3 pieces and sell 2 off to your mates. I don't have any mates so I sold it to Tim and Tony P instead….

The flashing is pliable and easy to cut, you can cut it with scissors. And being only around 1mm thick it's really easy to bend and mould to fit it into almost anywhere.

The best place to start along the centreline of the battery pack. It's logical really, thats where we've taken the weight out, so we'll put it back in around there as well. Cut yourself a strip of flashing 40mm x 165mm, then bend it in half. This piece goes INSIDE the two chassis halves and wraps around the battery cavity and puts all its 100gm weight dead along the same place that it came out of. You may need to do a little extra trimming to get it all to fit but it should be close enough.

This is probably the biggest single piece that'll you'll use

I like to hammer it all nice and flat before I bend it.

And with a little bit of bending and trimming it all fits neatly in

Now we're going to add some more weight along the batterys centreline. Cut some more pieces of flashing, this time 25mm x 45. Fold these over 3 times as shown. These ones go on top of the battery holders hard up against the chassis. Once again these are along the centreline of the battery, and also concentrate the weight on the centreline of the chassis as well which is essential for good handling. These 2 weight are attached with double sided tape and weigh in around 20 gms each.

This one is set for 3 folds, but you can fit 4

Fold em over, then hammer them flat.

Then stick them on with double sided tape

Next place to start is the bumpers. You've more than likely got one front and rear, so you can add the same amount inside both and you know that the balance will stay the same. So stuff them both as full as you can. The good thing about sticking weight inside the bumpers is that it's almost impossible for it to come out too! I used two strips 25mm wide and about 50mm long. I bent these into a V shape and stuffed them inside the bumpers. Then I built a 2 thickness version of the battery holder weights and stuffed them INSIDE the V shaped inserts as well. All up weight around 28gm in each bumper.

You'd be surprised how much will fit inside the bumpers

And once in there, it can't fall out.

The last place is also an easy one, right on the battery itself. Most Lipos that fit in Minis have a depression in the top. Certainly the Orions and the Yeah Racing do. And..a strip of flashing fits right in there perfectly. Fix it in with thin double sided tape, or even glue, and you've got yourself another 45gms smack where you want it.

This is where it goes.

And then glue the label back on top again.

Total all up? 237gms (give or take a few) of extra weight added, and it should only take about 30 mins to do. We checked the car after all the work and the balance came in at 60/40 Front to Rear, as opposed to 58/42 Front to Rear initially. Thats more than acceptable and maintains a similar balance to what the car had before.

One thing of interest is at a recent big race meeting here in Australia, several of us actually ADDED weight to our standard NiMh cars at a track that was giving us difficulty. And one of these cars WON the event weighing in well over 1400gms all up. So don't underestimate - the power of the weight...

WARNING WARNING WARNING WARNING WARNING WARNING!

Lead is dangerous stuff, it's highly toxic in some circumstances, especially after long exposure, or if for some reason it gets into your system. So...wash your hands, or even better, wear latex gloves and a face mask.