SMC's battery compartment weight system

0 Sept. 23, 2015, 2:39 p.m.

By Aaron Waldron
LiveRC.com

New from Superior Matching Concepts:
www.smc-racing.net

Brass Compartment Weight System
#3000, $13

Off road is all about managing bite. And 2wd takes this to the extreme. Often times we find ourselves tuning with weight before we even get to oil and springs as it’s a courser adjustment. In fact, right after the importance of tires, our buggies need the right weight, and weight distribution, to get the best lap times. With the advent of mid motor 2wd buggies and trucks, we find ourselves adjusting weight distribution regularly.

One popular type of weight increase is switching from a shorty pack to either a saddle or square pack. This gives us a quick approximate 60g increase in weight. The drawback is that it shifts weight forward or back if the shorty configuration was anywhere but right in the middle of the battery tray. And in low or very high bite, the weight distribution change can negatively outweigh the benefit of the increased weight.

We at SMC race off road too, and have been limited by just this dilemma. Hence was born the idea of the battery compartment weight system. By keeping our shorty battery and replacing 2mm of battery compartment foam per brass weight, we can now add weight in a central location, keeping the critical front/rear weight distribution the same, and only tune the overall weight. Each brass piece is 30g and 2mm thick, allowing multiple weights to be stacked on one or both sides of the battery to tune overall weight.

As a typical saddle/square battery weighs around 60g more than a shorty, center the shorty in the tray and add two 30g weights, one in front and one behind the shorty, to get the weight advantage of a square without changing the weight distribution.

The accompanying photos show one of our race Yokomo YZ-2 cars. The first photo is of the car with a 4400-2S shorty pack installed all the way to the rear (the foam spacing blocks and battery brace are removed for clarity). The weight distribution is 38.34% front with a total weight of 1557.7g.

Photo 2 is of the same car with a 5800-2S square pack installed. The weight increases to 1617g for a 59.3g increase, but the weight distribution also changes to a more forward bias of 39.02%.

Photo 3 is of the 4400-2S shorty again, but with a 30g plate in front and one in the back. The overall weight increases to 1619.4 for an increase of 61.7g. However the weight distribution is virtually identical with 38.58% forward bias. If both weights were installed behind the pack, the weight distribution would be exactly 38.3% as with no weights.