Good ways to lose weight from a Capra?

[TheLetterJ]

I've been running my Capra on 2.2"s since I built it (Oct 2019) and decided it was still driving too similarly to my dialed-in Wraith. I decided that 7lbs 4oz was too heavy and that I needed to put the Capra on a diet. I just swapped out my aluminum beadlocks for a set of the new orange Crawler Innovations 6 bolt wheels and glued my Ibex's on. I lost 20oz off the car in the process (there was a wrap of weights on each front wheel too) which is a big step in the right direction, BUT all that weight loss came from down low and my car handles like chit again. Currently sitting at 5lbs12oz without battery, 6lbs with. I'd like to see it at least 1/2-1lb lighter, but perhaps more importantly, with a lower COG (it did drive nice and predictably before), but I'm not sure how realistic that goal is while still looking like a Capra?

I've been thinking about switching to 1/8" titanium upper links and 3/16 titanium lower links, but that's pretty much smack dab in the middle of the car. Might be able to shave another 6oz or so that way... if nothing else, I suppose that would at least allow me to add a little more weight down low while maintaining current weight. I'll pull the empty fuel cell too, but it's lighter than it looks and I'll want to add a brace in its place between the rear shock mounts. I already have a flat skid (roughly 9mm higher) and trx4 shocks (roughly 7mm lower, softer springs have it sitting even lower still) to bring the cage down without losing belly clearance. I have 95g knuckles and 36g covers on the front along with a Treal 7075 billet front axle housing (~2oz heavier than stock) No weights of any kind on the rear. My battery is 4oz, and I'm running a Mamba Micro X and HH Puller Pro stubby, so there's not a lot to be lost there. OD front ring & pinion, UD rear ring & pinion keep the suspension sucked down pretty well, and also help keep the front end down when climbing, but it still very noticeably wants to backflip on climbs that it made before, while having nearly the same front-rear weight bias as before.

All that said, what are some clever ways to drop some weight from up high so that I don't have to add (as much) more down low? The goal is to still use the Capra cage... for now at least.

[themountain]

Too less of weight is contra productive ...its all about the distribution ;)

[TheLetterJ]

I wouldn't call it counter productive. But I completely agree with you about weight distribution. Sure, I took a step backwards (for now) by switching to a significantly lighter wheel setup, but in the long run, all else being equal, a lighter car will perform better. If I keep the same COG as I previously had (which is what this thread is really about) and same front/back weight bias, the car will require less grip to climb (climb things where less grip is available and a heavier car will spin), it will accelerate/decelerate faster, require less power to move (longer run times), be easier on components (making parts durability better, relatively) which in turn means some parts could potentially be replaced with lighter duty/lighter weight components and still maintain their reliability. There's more benefits to being lighter as well. Generally speaking, I'd want the car as light as possible, but with the necessary weight as low as possible, with a strong forward weight bias (60-70% on the front wheels.) You can overcome the loss of mechanical grip (vs a heavier car) by decreasing the tire's contact patch (narrower tires, though the Ibex's aren't terribly wide), which in turn will increase ground pressure, all the other benefits of a lighter car will remain. I can shift weight bias with changes in wheelbase, or just altering skid placement (longer rear links, shorter front) or minimize sidehilling rollovers by switching to wider hubs, but neither of those lower the COG. I have an 8lb+ Wraith that is still my go-to crawler, but I'd like to have a different driving experience. If my experimenting gets me nowhere, it's easy enough to put my old wheels back on and live with it. Having had 2 MOA's that fell in the 4-5lb range, I'm familiar with how a reasonably light car with well positioned weight drives. I'd like to move in that direction while keeping the Capra... a Capra.

I know the option of switching to a Sporty type chassis could make a big dent in this, but I'm not wanting to take that leap... yet. What about moving the battery on top of the links/directly behind the servo, or something along those lines? It seems like there might be some gains to be had in that? Has anyone done that (or similar) while keeping the Capra cage? I'm not looking for bolt-on/commercially available products, more just looking for ideas that could help me move in the direction of my goal.

[Mxkid261]

I think you kind of answered your own question regarding the sporty chassis if you really want to drop weight. Mine comes in at just over 5 lbs with a completely stock truck, sporty chassis, 2.2 ibex, and no dig. It really is the way to go with this truck IMO, but then its not a "capra" anymore, so I get that aspect of wanting to still keep it a capra.

[dusty husky]

I dropped about an once out of the cage by swapping in aluminum screws. I added it up and there are about 70 screws in the cage. Anyone that built a kit without a power driver knows that most of them are to long. Replaced the 3 x 18s w/ 3 x14s, 3 x12s w/ 3 x10s. Bought 50 packs of each for 11$ @ fastener express.com. I only replaced plastic to plastic screws which aren't 8n direct shear. You could go much crazier if you put together a full titanium kit but that would probably cost more than the truck.

[Hal]

I went with a sporty chassis. Huge weight savings. I'm at 4 lbs 4 oz RTR with battery. I know you don't want to go there. I did a lot with the cage, even removed some of the bars in the rear. Carbon fiber wheels lighter tires and foams. I put on Shaved, Cut and shut Rovers. The weight I had on the knuckles was crazy to get it to handle. I also have a Bomber as my go to trail rig at 6 plus lbs. The biggest weight savings I got was getting rid of the stock transmission. It's a boat anchor in my opinion, and it is geared way too high for a crawler, especially with 2.2s. I did a SCX10 / AX10 3 gear trans. Even with all the metal gears it was half the weight of the Capra trans with dig. And plenty of gearing to choose from. I have a friend who kept the cage and went with a 3 gear SCX10.2 transmission and he loves it. It doesn't even come close to the 5 lbs mark and is a very capable crawler. We are both still using plastic axles with aftermarket overdrive/underdrive setup. I did go to SCX10.3 rear axles to narrow mine a bit in the back but no knuckle weight there. I am at a 65/35 weight bias with my setup. My buddies is around 60/40 and it does great. If you are running an interior that is a great saving if removed. I am so anal I even do all my wiring as short as possible even shortening the servo and ESC wires. I can see savings of up to 2 ozs with just re-thinking electronics and wiring layout. I am running a TEKIN BXR that is de-cased. My go to for ESCs on lighter rigs. I am also only running a 850mh 3s battery. If I am competing it's a 500/3s. So some things to think about....wiring and electronics, possibly trans. Well that's my 2 cents anyway. Good luck, have fun even with a heavy rig.......its better than sitting home.

[TheLetterJ]

Thanks for the ideas.

I guess I hadn't really given any thought to a 3 gear trans being lighter, but I'd really only consider the switch if I kept dig. I'd certainly appreciate the added gear reduction. I do have another flat skid that is drilled for a 3 gear that I'd been considering using with a wraith trans I already have, or maybe even finally building a vp/hurtz trans.

I don't see it mentioned very often, but the chassis geometry of the Capra is damn near identical (maybe it is?) to a Losi Night Crawler I built for a friend years ago. Moving the servo to one side of the front axle and a small (600-850mah) 3s on the other made a noticeable difference on that. I've seen that same setup on a Capra based sporty (can't remember who sells that carbon plate?) but after staring at the front of the Capra cage, I don't see that working, unless...

I'm sure at some point I'll end up with a sporty chassis anyway and have been intrigued by the Krazed Builds Pnuema, or the more direct swappable High Altitude Shepard. The Shepard definitely makes it easier to get up and running since pretty much all of the Capra parts will still bolt up, but there's a good chance I'll slowly change out the rest of it (links, transmission, skid, etc) anyway so the Pnuema would still be a contender. It probably does make the most sense to just make the switch now and I can just slap a different body on top if I want it to remotely resemble a 1:1 vehicle. They do look good with an XR10 body on top though. The Capra cage would then likely find its way on top of my Wraith, win-win? Any idea what the Capra cage and/or a typical sporty chassis weigh? Any other Chassis' I should look at?

[Mxkid261]

I run an InTheWorks Cricket chassis on an otherwise completely stock truck, although I'm not running the dig unit. The chassis comes with the front axle servo/electronics tray, I just use it for the servo and a 650mah 3s pack. It works great but I don't comp so I'm sure there are nicer chassis' out there that people with more experience can suggest. I have an XR10 hardline body as well as a Losi Nightcrawler body that I use on it. Coming in at 4lb 14 oz rtr with battery and some added knuckle weight. I love it compared to the stock capra chassis. Also on 2.2 Ibex.