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iTrader: (12)

SERPENT Medius X20'21

Brian10811

iTrader: (1)

After driving the X20 at its release. I think these changes will greatly help this car. Even more so in the slower classes such as 17.5 and 21.5. I know a few things that I mentioned in the past has been addressed with these changes. Awesome and can't wait to get the upgrades. #GoSerpent

Airwave

iTrader: (1)

Honestly not sure what... I have the impression they have no idea what they are doing. Why change the front knuckles, what was the problem with the current ones? The rear upper arms support why not, but it is helpful only in certain conditions. I'm faster with the out-of the box setup configuration... And adding weight under the lower arms... What kind of effect are they hoping for? Heavier unsprung mass will be worst...

dawgmeat

iTrader: (8)

I was thinking the same thing with all the extra weight that’s been added to the front hubs. Too much unsprung weight

Johnny Wishbone

iTrader: (6)

There are a few reasons for the front hub change. The insert will allow you to raise or lower the axel which will change the angle of the shaft coming out of the outdrive which should help add or subtract steering from the car. As well as changing roll center. The other issue with the the original steering hub is the arm itself after extensive use can drop or twist slightly, thus the carbon revision. the rear upper arm holder is up swept so that you don't need as many spacers as most people run from 4mm up and when your running that many spacers you have to run longer screws first just so you get them into the bulkheads, the bad part about the long screws is that they are more prone to bending on side impact. The brass arm inserts should help with drive off of corners if used in the back or plant the front for better steering, but that is one to try to see if its true.

Brian10811

iTrader: (1)

Very well said Jonny Wishbone

TurnNBurn

A lot of the changes make sense time, TBH. The adjustable axle height at the hub -not much different from what’s being done in off-road to handle different surfaces. Likewise, the shims for the upper arm allows for RC adjustment from the outer upper arm, not just the inner suspension mount.

Technically, the weights for the arms would be considered “semi-sprung” weight - it’s not sprung weight because the lower arms is not weight carried by the springs, and it’s technically not unsprung weight, because it’s not mass that is rotating... Yeah,I learned something new this week while researching that. Anyway, the ‘21 includes a heap of weight options, including underneath the diffs where the existing “dogbone” chassis braces go, not to mention a weight that can get installed on the base of the updated Medius mount. It should be interesting. It’s just a shame that they changed so much to make an “upgrade kit” feasible... but, quite a few parts should be usable on the existing ride.

Brian10811

iTrader: (1)

I in fact I am glad they made all these changes. I see several things that can be updated on the existing kit. Even if I wanted to convert. The fact the best change was a stiffer graphite chassis is very good. I am excited to try the new knuckles

DBM

Unsprung weight isn't a big deal if you run on smooth surfaces. Arm weight can be considered 50% unsprung since the inside of the arm barely moves, where as the ouside of the arm moves almost as much as the wheel/tire/hub.
The axle height is always going to be dictated by the diameter of the tire being used...the height will always be half of the outer diameter of the tire. Changing the location of the axle in the carrier won't change the angle of the axle coming out of the outdrive for that reason. It will change your roll center, though.
I've always liked the suspension design of the X20. I really wish that this new version would have gone to an MMX/R12 type of motor mount and top deck design with both belts on the electronics side of the spur so that the spur. Maybe they'll do that for 2022.

Brian10811

iTrader: (1)

I totally agree about the top deck and spur mount. I run the R12 and wow that car is awesome. So easy to change spur. The 2 top decks is a genius way to reduce mid motor chassis flex. Not to mention very good tuning.

Airwave

iTrader: (1)

Interesting, my point is just that changing the width was already possible, change the rollcenter was already possible, not interesting.

I will preciously keep my upper-deck so I really hate asymmetric decks and it seems that AWX drivers are using strange upper-decks to solve the effects of the split decks lol

Johnny Wishbone

iTrader: (6)

Alright the 21 has been out for a bit what is the feed back so far?

I have had a couple runs on the car now and it has very good turn in, the car really reminds me of the AX MMA. It is also very quite, my cars in general are pretty quite but this one is very very quite, and feels like it glides thru the corners.

On the build here are the things to look out for;

First, I never use the given link measurements in the guide as I put the final built car on a setup station. The steering lock makes setting the front end steering easy to do, its a nice touch.

Page 4 suggests filling the diff to 11.5 grams, not sure if my scale was messed up, but the empty diff came in at 13 grams so I just did the normal fill to the cross pin and called it good.

My only gripe was that those e-clips for the DJC and the CVD are very small and it would have been nice if they included a couple spares.

The 1mm claw spacers for under the lower suspension arms make it a lot easier to set roll center now.

Page 11, I ran into the spur gear being really close to the motor mount. I put a 0.02mm shim between the big bearing and the aluminum pulley to get the gear out just a bit. With that I also used a 0.02mm shim on the M3x4 screw that holds it all together. I also replaced the R9 c-clip with a external retaining clip, it just makes it easier to remove and replace gears this way.

Page 12, i used the 2 supplied 12x15x0.25 shims between the bearing and the excenter holder. I do this because the big side of the diff is really close to the bulkheads and could create drag.

Page 13, I use front upper arm in both the front and rear of the car, just a personal preference and no performance advantage, I do this as it give more material for the pivot ball assembly to screw in. I also replaced the M3x10 button head screws on the big side of the diff for M3x10 cap screws. The cap screws have a small diameter head which helps with the diff clearance.

Page 21, i used 0.01mm shims between the steering levers and the drag link on the M3x6 screws as without it felt like it had a bit of stick to it.

Page 26, build the shocks as normal, (I polished the shafts prior to assembly) but be wary of the amount of o-ring lube used as I had one shock that felt a little tighter than the other 3. It turned out to be just a little too much lube that when the lower cap was screwed on squished the o-ring enough to cause that drag. Cleaned out the little excess and the shock was perfect.

All in all the car built great, and there was no excessive trimming or filing required.

The car drives like it has great potential and time will tell.

Brian10811

iTrader: (1)

That is a great review Jonny Wishbone. I think these improvements will help it alot. Did you run the same setup that you had on the previous version X20?

Johnny Wishbone

iTrader: (6)

I used the out of box settings for the shims supplied with the car, but altered droop settings, width and spring selection. From the runs I have had on it I think the shock oil needs to be increased as well. This is all on CRC Black carpet with pretty high traction.

Johnny Wishbone

iTrader: (6)

Any setups or build pics, feedback?