Chassis thoughts... vertical, or horizontal batts

[zeropointbug]

Hey, im almost done designing my new chassis. I was wondering on one thing though...

DISREGARD THIS MESSAGE, measurments were typed in wrong... right measurements on my next reply!

I could have horizontal batts (A123 cells), and make the chassis plate ~240mm wide (also more plate material), or stand the cells on edge close in next to the braces and the total width would be 165mm.

My question is do you think 240mm is too wide? Will this hit the ground if landing at an extreme angle, or bottoming out? The 240mm one will have a lower CG, while weighting in a little more, the 165mm will have higher CG and lighter (not by much). Anyways, like to hear any experience or thoughts about both setups.

BTW, its 5 M1 cells per side, 10 total (700 grams)

[BrianG]

It's hard to say really. I would mock a bad landing by compressing the suspension at the max angles (side to side, front to back, etc). Just protect the bottoms and some of the sides and you should be all set.

Another thing; you mentioned standing them up. I was thinking of doing that for my Revo but not sure if the CG would be too high. Something to think about...

[BP-Revo]

Well, lay down would mean a lower cg, but a less centralized one. The closer the weight is to the centerline of the chassis, the better it will handle because there is less weight transfer. The same concept is applied to full size cars.

For example, in an F1 car, the fuel tank, engine, driver, shocks, and pretty much everything is between the front and rear axles, and well within the edges of the tires. Most of the side faring in an F1 car is to reduce drag on the rear wheels and provide an area to house the radiators...thats about it.

[Serum]

The narrower the chassis, the faster your car is capable of doing turns. putting heavy weight from the batteries far to the sides will decrease the corner-ability..

[zeropointbug]

OOps
OOPs

I must be really tired, i don't know how those measurments got in there. :025:

The wide chassis is 190mm wide, and the narrow version is 115mm wide.
I just noticed that the body (crowd pleazer is only 160mm, so 115mm version it is... it does give protection against rocks thrown at Quark esc. (will have massive heatsink)


Also, what kind of front-rear balance should i be considering? The motor is closer to the front (15mm forward), so should i mount the batts slightly back a bit?

[Serum]

Well, my previous post still is counting;

If you put more weight to the front, you will be able to turn in the rear of the vehicle in corners. While put more to the rear, understeer becomes a fact.

Best way to decide on what you like; make some easy to adjust battery-trays which you can shift easy. The reason why i made the proto-type of the CD savage i posted you earlier. It's hard to tell what the perfect position is. But overall (from my personal experience) slightly to the front takes care of business pretty well.

[zeropointbug]

Okay, then i think i will go with a balanced front/rear ratio, it actually works out good then the batts aren' tin the way of the spur gear mounting/removal.

I will post print of the braces, and plate later. I am making the braces out of 6061-T6 alum. and the bottom plate out of 7075-T6 grade. The braces each weight in at 40 grams, the plate should weight 120 grams.

...for whats its worth i stood them on their side in the Hellfire...Laid down they were too wide for my liking...This was regular 6-cell nimhs...

I was wondering the same thing, but with lipo's. Is it ok for the packs to be mounted on their side? I'm in the middle of a conversion on a CRT and setting the lipo's on thier side seems like a good idea. Sorry to hijack, it is kind of on the same topic though.

[zeropointbug]

hijacking, don't be silly, this is a forum.

I have decided im mounting vetical batts (on edge), so there wont be much of anything for a lower chassis deck. This will be pretty light, competitive with the gorrilla maxx chassis. It will be one killer truck.

Also, serum, i made the the center shaft/spur gear holder future proof, in case i ever want to use a center diff. or whatever. The CG will be low also, the motor sits 45mm lower than stock.

BrianG, do you think 2.5mm alum. plate about 6cm wide by 10cm (for Quark, thermal paste) which would be screwed along the 10cm length to the chassis brace. Or do you think some thicker plate alum. and then i machine it to heatsink fins, passive of course. What do you think?

[BrianG]

Generally, the thicker the plate for a heatsink the better (to a point). You need thermal mass to pull the heat away, then fins to dissipate it. I would use 1/8" thick aluminum, but maybe not so long/wide. Using the chassis as a secondary heatsink is always a good idea, but I don't like to count on it.

[zeropointbug]

Well then maybe i'll use the same 6mm stuff the braces are made from and machine fines into it (3mm) and the other 3mm for heat spreader. This should keep the thing as chilly as a male penguin waiting for his love to return. :005:

Also, im curious, do you have pics of your E Revo by any chance?

[BrianG]

Yeah, I have some pics: Pic1, Pic2. The colors are washed out because the camera I used at the time was kinda crappy.

[zeropointbug]

That's one nice setup man. But hey i thought you said you had your Quark's heatsink on the bottom of it?

Also, im just trying to remember who was it that did the Quark mod, you and who else?

[BrianG]

Thanks!

I do have the heatsink on the bottom. The heatsink is a 1/8" thick piece of angle aluminum with extra heatsinks epoxied on top. This allowed me to mount it the ESC on its side to save some room. The pic below is a little different than it is now (the top HS are different and larger), but you get the idea...



Smertzhog (I hope I spelled that right) did a mod where he attached super large heatsinks all over it. Jhautz machined the heatsink found here in the store. Maybe one or two others have done some type of mod, but I can't remember off hand.