Artificial-I

iTrader: (17)

Yeah I knew there was a 3.0 , reason why my lhs had a ton of them and I would always sift through and say. Where are the 3.1's.

Had to go out and order one.

ProE

for the guys that using the 2005 kit. what battery do you use and where do you fit it onto the car.

With the stearing servo that moved to the centre now, the battery could only go where the serve use to be. ????????

Is the battery heavier that a servo, and wouldn't that transfer the weight more to the side of the car?

Rapid Roy

The battery has been moved to where the receiver box used to be. You want to use a light weight AAA pack in a 3/4 configuration. The HPI one has about the best capacity as well as being a bit lighter then others. The receiver mounts where the servo used to be.

Chris West

omg , if you click on the details and scroll down for the 200mm version its got 3.1 there is no 3.0 for gas it even says 3.1 on the body bag

AMGRacer

Yeah I thought long and hard about this for the same reason. You cannot use the "old" battery type, the AA style, it has to be the AAA style in the 2+3 hump pack type of configuration. The instructions say to tape it to the extra bit of carbon on the top deck, I glued mine to the chassis.

You are right about the battery being in a "worse" position, here are the weights of the items in my car:

Sanyo 900mah pack - 68g
9550 servo - 40g
9451 servo - 58g
Receiver - 11g
Fuel tank full of fuel - ??g

If you look at the new design closely it moves the 40-60g (depends on what servo you use) steering servo dead centre, BUT also lowers it right to the chassis. Other designs require the servo sits 2-3mm higher than the chassis bottom to prevent it scraping during cornering. The battery pack is now off centre, its where the receiver used to be, but it is only 10-15g more than a servo AND is much closer to the centreline than the old steering servo was, so there is an overall net gain. The battery is also right on the chassis plate.

The throttle servo remains in a similar position as before, and the receiver now is possibly a little further out (not much) than before, but mine weighs only 11g.

Another gain from the layout is the fuel tank is now further forward making it much easier to fit any motor to the car (there is heaps of clearance now), adding more weight over the front wheels and also the bulk of the fuel now sits below the chassis. The tank from the top looks about the same, but whereas before there was only a small area that wrapped around the battery, there is now about 50% of the total tank volume (perhaps more) below the chassis plate, a significant gain in lower cg. The tank weighs at a guess 5g (i am purely guessing here) and given 1 cc of water weighs 1g (approx) the full tank is around 80g. Getting 40g under the deck rather than say 20g is going to help.

Lastly since the top deck is now bolted together with a plate it is overall more rigid than it was with the receiver box in place, and the lower chassis is also much more rigid since it is a single continuous piece of alloy. It is also more narrow by around 2-3mm where it tapers towards the front of the car.

B.LaFrance

Where can you get the HPI AAA battery?

Artificial-I

iTrader: (17)

Very good evaluation of the car , enjoyed reading that.

ProE

It doesn't make any sense at all if you look at the changes. The engine sits mainly on the left side of the car. Now the battery that was positioned in the centre of the car is also moved to the left of the car. The servo is moved to the centre.

So what they've done, was to move everything to the left of the car and the only thing that is still on the right side is the one servo and your receiver, which is the smallest of all these items.

The fact that they changed the shape of the fuel tank to lower the centre of gravity is also going backwards. With this change to the tank the battery needs to be of a different shape. The old battery was flat with all five cells in line and on the floor. With the new design the battery will have to be a 2/3-configuration battery, which mean that two cell move higher up in the car, moving the overall centre of gravity up again. These two cells definitely weigh more than the volume off the fuel that was moved to the bottom, as the density for the battery material is much higher than the density of the fuel.

Its more of a scenario where they tried to make it more easier to work on the car, instead of taking the actual vehicle dynamics of the car into consideration.

For the guys that are the experts on set-ups I have the following question.

IS IT BETTER TO TRANSFER MOST OF THE WEIGHT OF THE CAR TO THE LEFT HAND SIDE, IF MOST OF THE TURNS ON THE TRACK ARE RIGHT AHNDERS?

I would actually like to know what HPI’s response would be. (From the technical department and their sales departments b..l s….t

Rapid Roy

Here is the HPI pack

Rapid Roy

Now are you basing your opinions on the actual left to right weignt distribution of the original R40? Does the original design have more weight on the engine side? I am curious to know if you have done this. Also, how does removing the battery door and wedging everything under the top deck make it easier to work on?

HarKonnenD

iTrader: (23)

Hmm. I must find out the rating on my trinity pack I posted. Having a hard time trying to find it. Sucks for them not to lable the capacity on it as a reminder.

ProE

No, dont get me wrong here. Im not bashing this car. You guys convinced me to buy this car over other cars. So then I must like it better. I asked these questions (more made statements) about this 2005 kit. As all the previous info that I recieved and search for on the internet convinced me that this is a good car. Or up to what ever version you guys are using.

Lets say that the previous versions before the 2005 kit was perfectly balanced. Why would they move all the stuff around.

Im still building this kit (90% there). only need to fit the engine. I've placed my car on a balancing device, and it tend to lean to the left already,without my engin and pipe fitted.

If you read my last line again you would see that it is actually the same as your comments. (sorry, left the not before sales department out) HPI claims that all these changes will make it easier to work on car.(marketing stuff) I've seen the previous versions, and build this version and I would say(my opinion) that it is defenetily not easier to work on. What is your opinion to this?

What is the run time on that HPI 800mAH pack. Will on off them last for the whole day?

Rapid Roy

Hmm... I've gone back to look at the build pictures on the previous page, and from the picture of the bottom of the chassis, it looks like the bulk of the tank has been shifted over towards the steering servo. If you look at the bottom view, you can see how far over it is. This, along with the lighweight receiver pack should balance things. Sorry about my other post, I get a bit snappish when too much bench racing is happening. It would be great, as you posted, to hear from HPI about the new weight distribution. Maybe Thad is lurking around here somewhere.

ProE

You might be right about the fuel tank. Had another look at mine. It is about 33mm wide.

The offset from the left side of the tank is about 8mm. So if I do my maths correct that is about a third of the tank to the left of the centre line.

So lets say we take symetry into concideration, that third would balance the middle third out. So we are left with a third of the tank starting at about 8mm offset from centre.(about 5/16 of inch).
If the tank carries 75ml, a third of that, 25ml( lets say 25g estimated) of mass will be distibuted from one side of the car to other in going from full tank to empty tank.

I did try to balance my car with an empty tank, so I guess that that would change if I fill the tank up.

Still sound scary. Maybe someone in this forum with both models can try and compaire these cars for us.

AMGRacer

As you clearly dont believe my posts I will also not waste any further of my time answering your speculation while I actually have both chassis to measure and 2 years experience racing them. I would suggest finishing your car and balancing it like I did.

Let me just also add that I have put my car on balancing posts (as I always do I am not a n00b) and surprise suprise the car is almost perfectly balanced down the centreline in fact better so than the 2004 was.