wallacengineering
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Hello, my name is Josh. Im nee to this specific forum but certainly not new to RC or RC forums. I have been doing RC for just over 16 years, and am a part of several FaceBook Groups including Arrma specific ones as well as several others.
Now let me start out by saying I think Arrma is a great company. I discovered Arrma in late 2012 seeing someone in college with one of their monster trucks. It could have been a Nero, but Im not sure. It was certainly large, larger than 1/10 scale for sure. Ever since I saw this truck, Arrma has been my favorite brand. I personally started out with the Kraton RTR Ver 2.0.
Ive owned more than 10 Arrma vehicles over the years, including the Kraton RTR 3.0, 4.0, the Kraton 8S, and most recently I got a 1/8 Kraton EXB (Ordered as soon as they came out). As you can probably guess, the Kraton is my favorite RC of all time. The Truggy layout, impressive handling, strong suspension, and great RTR ESC and Motor drew me to the platform. However, while I can definitely enjoy my Arrmas, I must admit that they can be very frustrating, and now days I even find myself wondering if I should just start considering another brand as my favorite. And now Im going to explain why I started this thread and why I am starting to loose faith in Arrma RC.
They break and have issues, often very expensive issues, far too often, and thats all there is to it really. I mean come on, I took out my Kraton 8S ONCE for 5 minutes and shattered both the front A-Arms on the third jump and in less than 5 minutes. Mind you, this was already the updated "Ver 1.5" with the split Tower-to-Tower Brace and rear chassis reinforcement plate. This occurred at a 1/8 scale outdoor track, on a mediocre sized jump, and the truck went at most 3 feet high off the ground. As it was brand new, I was driving the truck quite gently and had barely even touched 50% throttle. All I did was hit the brakes a bit too early in the air and the truck landed nose-heavy, I would say about a 20° nose-down angle, not a nose-dive by any means. You can probably imagine my dissapointment and frustration after this incident. Here I was, just having spent $1000 on this truck and it lasted all of 5 minutes.
Obviously I contacted Arrma regarding warranty, and they tried to say it was abuse and refused to replace them. As a result, it has sat on my shelf for 6 months now, only having been driven the one time, because I refuse to pay for the parts on a brand new truck. Also, I snapped a screw head off the center diff attempting to change the fluid, and now I need a whole new center diff for it because if I drill out the screw, I will damage the threads and render the case useless. All of this because Arrma doesn't know how to use locktite properly. I tried heating up the diff with my heat gun, no dice. I even tried resting my soldering iron tip on the screw head for so long that the entire diff got hot to the point where I could not hold it with my bare hand, and still broke the screw.
Now with my EXB, theres the obvious diff issue that so many owners have been experiencing. I shimmed my diffs, but it didn't help. The open rear diff broke with 0.75mm worth of shims underneath each sun gear. The outdrive shaft had ZERO play when pulling and pushing, and spun completely freely with almost no resistance whatsoever. I can promise you that my shimming was as perfect as it gets. The diff felt great too once assembled with fluid, yet the internals still wound up destroyed. Then, my center diff (which has LSD plates) was also destroyed, with the same perfect shimming applied. At this point in time, I have destroyed 3 EXB differentials, all having been checked and shimmed properly, and the truck has been built and running for maybe 6 weeks. That is simply rediculous. Im considering fixing it one final time and simply selling it at this point. I know Arrma has ceased production and is working out the issues but the fact this truck even got released in the first place tells me that Arrma never tested this truck properly before release, especially not on 6S power.
Arrma needs to just go back to standard diffs in the EXB. The LSD thing is dumb, it weakens the drivetrain overall and you can achieve LSD effect with thicker diff fluid. Its just a gimmick that compromises the integrity of the diff internals. Its a dumb idea and it needs to go away forever. It has done nothing but either ruin the handling of the truck because you can't predict how severe the limited slip action will be, or it has broken the sun gears time and time again because the tabs that hold the circular plate in place on the bottom of the sun gear are so thin, that when the diff lock activates and power is sent to those sun gears, they shear off almost immediately, see photo below.
I also had to modify the front end, removing the upper pivot ball spacer and grind down the lower A-Arm spacer and plastic underneath to eliminate the resulting extreme positive wheel camber, all to just bring the dogbones inward a mere 1.0mm so they wouldn't pop out of the front diff cups anymore. I also noticed there is simply WAY too much play in the bearings on an assembled diff. Take a look at yours and wiggle your bearings back and forth on the output drive hole. I used a Kyosho 96644 shim over the outdrive hole before the bearing, then assembled the diff, to determine that there is 0.20mm of wiggle/play in each bearing. This means that even if you shim the bearing from the outside using Tekno TKR1222, you need at least 4 shims to completely eliminate diff wobble, and still need to adjust from there to tighten the ring gear mesh with the input gear inside the bulkhead.
Now I have tirelessly worked for weeks to come up with solutions for my Arrma Trucks and I also believe I have discovered the reasoning behind such issues. As for the 8S Arms, I believe Arrma has not altered the composition of the plastics AT ALL from the 6S models, instead simply choosing to enlarge them in an effort to save money. As a result, the plastics on the 8S are far too brittle. As evidence , observe the photo below. You will see that the arm broke off so cleanly that it didn't even scratch the hinge pin, let alone bend or break it. This should be a clear indication as to just how brittle they actually are.
Now of course these are just a few of the issues with Arrma vehicles. I also own 3S and 4S Arrmas and if I were to write down every single issue, I could write a novel. So to shorten things up, below is a general list of ideas that apply to all Arrmas in specific categories to make them much stronger and easier to work with, and that will make them as strong, if not stronger than the competition. Because of my specific preference for the EXB, I have studied it and measured things especially and have more specific ideas regarding it. So lets get started with my suggestion for an Arrma 1/8 Kraton re-design:
Arrma 1/8 Kraton EXB Design Suggestions:
1.) MOST IMPORTANT: The Drivetrain of the EXB and in fact, the entire 3S, 4S, 6S, and 8S line-up of vehicles, needs to be redesigned an enlarged. I know you guys just redesigned the diffs for the EXB but unfortunately the design is still not even close to the strength of the competition. If you want a good emaple of a properly sized diff, take a look at the Traxxas 1/10 Maxx diffs. Keep in mind that these diffs were made for a truck that runs on 4S LiPo, and yet they dwarf the Arrma 6S diffs. However, I do not believe this rediculous size is entirely necessary for 3S or 4S vehicles. I have suggestions for all Arrma RCs but lets start with the Arrma 1/8 Kraton EXB.
Currently, the new EXB plastic diff cups are 29mm in diameter and roughly 20mm in length not including the outdrive hole. This is JUST the cup, NOT an entire diff assembly. I believe proper sizing for a 6S diff cup would be at or just under 40mm in diameter. In fact, the 38.50mm diameter of the new EXB Diff Ring gear would actually be quite perfect for a plastic diff cup. The length should go up from 20mm to 25mm or maybe even 30mm to acommodate larger internal gears. Of course, the thickness of the actual plastic material should be maybe 0.50mm thicker as well, as there have been several reports of overheating diffs and melting plastics. The overall volume of internal diff fluid should go up by at least 50%.
As for new gear design - the current EXB diff sun gears are 18mm in diameter. 22-24mm would be more appropriate considering the power of modern brushless systems. Similarly, planetary gears (A.K.A "Spider Gears") should increase in diameter from 12mm to about 14mm or 15mm. In all cases for all gears, be sure to increase tooth width and hight as well as engagement profile to suit the new sizes, plus increase the thickness of the gear bases to further boost durability.
2.) Diff Outdrive Cups as well as shims need to be redesigned. This would also apply to all other cups on the vehicle. The problem is less with diameter and more with material. We all see how quickly the dogbone pins eat into the diff cups and those cups end up needing to be replaced quite often. Use a stronger steel, one similar to Robinson Racing Xtra Hard Pinion Gears. The increase in diff outdrive shaft diameter from 5mm to 6mm from the RTR to the EXB is a welcome upgrade. The increase in retaining pin diameter from 2.25mm to 2.50mm is also a great change. As long as we can get stronger material for the cups, I believe the size of the EXB outdrives is large enough as is.
As for shims, the outer diameter is always too small on Arrmas. The outer diameter of a shim should always be just a bit smaller than the gear it is shimming. For example, on the current EXB, the stock smaller shims are 6mm ID x 12mm OD, while the OD of the sun gear is 18mm. Instead, these shims should be 6mm ID x 15 or 16mm OD for more Sun gear stability. Similarly, if Arrma increases the Sun Gear diameter to, say... 20mm, then they should use 6mm ID x 18mm OD shims. All shims should always have the same ID and OD to promote sun gear stability, while thickness can vary for proper adjustment. Arrma should also offer various shim sets to accomodate. The Kyosho 96644 shim set includes 10 x 0.1mm, 10 x 0.2mm, and 10 x 0.3mm shims in the kit for a total of 30 included shims. This is a great kit and Arrma should do the same with its Diff Sun Gear shim sets. So Ideally, for a 20mm Sun Gear, a package of 6mm ID x 18mm OD shims in 0.10mm, 0.15mm, and 0.20mm thicknesses (10 of each) would be perfect. And if Arrma is going to continue being lazy and not testing shimming before the truck leaves the factory, then one of these shim kits should be included with each Arrma RC free of charge.
3.) The EXB external diff gears (Crown/Ring and Pinion/Input) also need a boost. Yes, the new design for the EXB is a big improvement. The larger contact area is a huge upgrade, but I believe this needs to be taken a bit further even still. The current contact patch or tooth length is 5mm. A decent showing, but 6mm would be ideal. The Input/Pinion gear should be ever so slightly shorter with teeth that are 5.8 or 5.9mm long so that the input gear can be shimmed outwards towards the diff cup to get the thick end of the gear teeth fully engaged onto the ring/crown gear. If there is input gear teeth sticking out from the ring gear, it needs to be shimmed inwards. Additionally, each tooth should be just a tad bit thicker. In fact, the Ring and Input Gear teeth should be identical in thickness and strength as the Module 1.0 Center Diff Main Spur Gear Teeth. The same increase in contact patch/tooth length to 6mm would be appreciated for the Center Diff Main Spur Gear too. As for gear ratio, the current 4.3 Diff Input Gear turns to 1 Ring Turn is pretty perfect and allows us to run average-sized Pinion Gears in most cases. Same goes for the Center Main Diff Spur Gear. The current amount of teeth is pretty perfect. In fact, a larger diff size would raise the position of the Diff Input Gears and almost perfectly line them up with the center of the driveline anyways.
4.) Thicken up all the dogbones on ALL of the 6S vehicles including the EXB just a bit. Currently, the 6S dogbones are just a bit too prone to bending at their current 5mm diameter. 5.5mm diameter would likely be enough of an improvement. Also, adjust the lengths so that there isn't so much slop and movement in the cups.
5.) Get rid of the LSD diff design for reasons I discussed earlier. Also, get rid of the "Safe-D" Input Gear Shaft Cups, or enlarge the grub screw. The RTR cups are stronger and easier to work with because of the larger grub screw.
6.) Shorten the truck by just a bit, both in overall length and in the chassis and wheelbase. The thing is, bashing truggies do not need to be quite a long as actual race truggies. Shortening the truck has several advantages - the removal of material reduces the overall weight of the truck as well as reduces the possibility of bending longer parts such as the chassis and tower-to-tower brace. However, we do still want the Kraton to handle like a truggy, so I would say only a bit. Here are a few examples: Currently, the overall length of the EXB is 604mm. It should be entirely possible to bring this down to about 590-595mm. Meanwhile, the wheelbase should be brought down from 377 to 370mm and the chassis should also be shortened by about 5-10mm respectively.
See, the average basher won't even notice the difference in the length, its such a small amount that the truck will handle almost exactly the same, and yet there will be a noticable difference in durability and weight. Even when people build Kratons for racing, they never make it to professional levels. The Kraton is a basher and is far too heavy for anything more than casual club-level racing. Therefore, this slight shortening in the overall design would have nothing but positive results and no negative results.
7.) Beef up the 7075-T6 aluminum chassis and shock towers just a bit further. The move from 6061 to 7075 aluminum was a great move on Arrmas part, especially for the long and heavy Kraton. Its also a change that Arrma fans all over the world have been waiting for, for many years. However, people are still bending these parts ocassionally as their thickness isn't quite on par with competing truggies, although its very close. However, they don't need to be too much thicker to close the gap in durability at this point. I belive a 3.5-3.75mm thick 7075 chassis and 5.5mm 7075 shock towers would be more than strong enough. With this slight increase in thickness, the truck would be nearly indestructible. You could even then reduce the thickness and profile of the aluminum chassis braces a bit because the chassis and towers would be so incredibly strong that the truck would theoretically hold up to light bashing with no damage using no tower-to-tower brace whatsoever and possibly even plastic chassis braces. However, please keep the braces aluminum. The Tower-to-Tower brace is already prone to bending so leave its profile as-is.
These suggestions for the EXB can be applied to all 1/8 scale Arrma 6S vehicles but of course with necessary changes for each model. Now, lets move onto suggestions that apply to all Arrma models in general:
1.) Make every model into an EXB design. This includes ALL 3S, 4S, 6S, and 8S vehicles. "Mega" Brushed vehicles don't really need any redesigning. The Kraton EXB renders all current Arrma RTRs completely worthless and obsolete. If you want to sell RTRs, then throw RTR electronics into EXB models and sell those instead of RTR plastics and aluminum. Offer an EXB model of every car (offroad at least) and they will sell like hotcakes (or at least they will when the drivetrain actually holds up). Continue offering rolling chassis as an option and extend that to the entire range of cars. Being able to choose your own electonics is a massive advantage for Arrma since almost every hobbyist upgrades their electonics at some point anyways.
2.) For the 3S and 4S models, its time for metal diff gears. The plastic composite gears just aren't good enough for 3S+ brushless power. In fact, the current 29mm EXB diff design would be perfect for all of the 3S and 4S 1/10 scale models. This gives you a way to repurpose the new EXB diffs so that they do not go to waste, provided that you get rid of the defective LSD system in favor of standard, flat-bottomed Sun Gears and traditional diff design. The current plastic diff gears found in the 3S and 4S models can be used for brushed "Mega" models. As for 8S models, the diffs can be increased in size similar to my suggestions for the EXB and 6S models. However, the increase in diff size may not need to be as drastic for the 8S vehicles since the diffs are already quite large.
3.) For 3S, 4S, and 6S vehicles, ever-so slightly softer plastics would be a great upgrade. EXB plastics do NOT need to be any thicker, just slightly softer so that they flex rather than snap under heavy stress, quite like RPM parts. As for 8S vehicles, the plastics need to be softened much more drastically. After my experience with the Kraton 8S, its clear that the A-Arms are pretty much entirely worthless as it currently stands.
4.) IN GENERAL, Stop using so much locktite on your screws! Please Arrma, understand that locktite is simply used to stop a screw from vibrating out of metal threads, thats IT! Threadlock is NOT intended to reinforce screws or threads AT ALL. All you need is standard, watery blue loctite, such as Vibra-Tite 121, applied to 4-5 threads of a given screw in a LIGHT coat to secure it. That goes for ALL metal thread screws regardless of design or part its holding together. When I tried to pull apart my K8S center diff, the screw broke due to the rediculous amount of super-thick blue locktite that was used. Each screw was entirely coated top to bottom with a VERY THICK coating. There was so much powder left behind that it filled the screw holes as I pulled the screws out. Thats just rediculous. The ONLY exception to using Vibra-Tite 121 and in very small quantities, is cup and pinion grub screws. In this case, a medium-high strength and high-temperature specialty blue locktite such as Vibra-Tite 123. It is more than strong enough. Ive NEVER lost a pinion gear while using it on the grub screw so long as I give it 24 hours to properly cure. There is NEVER, EVER a nedd for red locktite, EVER! Red locktite always does more damage than good, constantly causing the stripping of screw heads.
5.) The New Kraton EXB comes with a heavy-bash-ready front bumper/skid plate design. Arrma should also but this design in the rear of the EXB. It makes no sense to have the front end so well protected but then the rear is left wide open to damage. These bumper/skid plates should be added to every single Arrma no matter how large or small or the power system. Every basher crashes his/her truck sooner or later. Its enevitable, so protection is a high priority.
6.) Similar to the Kraton EXB, the Big Rock 3S should also be shortened ever so slightly in the persuit of less weight and better durability. Same goes for the Kraton 8S and 4S as well as any other long vehicles.
7.) Get rid of the Spectrum STX-2 radio system entirely from ALL models. Its a terrible radio. Include some other radio instead on RTR vehicles.
8.) Include better servos on RTR models. The current servos are okay but come up a bit short. Increase 1/10 models from 7KG to 12KG, and 1/8 models from 15KG to 20KG. This should be plenty enough to satisfy owners for quite some time.
9.) Offer a wheelie bar for those who desire a less extreme wheelie angle.
Well, thats my list of suggestions. Fellow enthusiasts, please tell me what you think of this. Remember that the more you comment and share, the more likely that Arrma will take this list seriously. Arrma, it is fully understood by both myself and others that an increase in price will be necessary to make this happen as well as the fact that it could take years to implement, especially if you are updating all the vehicles. When it comes to pricing, just try not to let it get too rediculous. For example, the 1/10 Traxxas Maxx costing the same $550 as an RTR 4.0 1/8 Arrma Kraton is a pretty rediculous prospect. That being said, I would be more than willing to pay $550 for a 1/8 Kraton EXB roller if it had ALL of my redesign suggestions on it; and if it did NOT break straight away out of the box. If it held up like a Maxx does, It would be more than worth the price.
Now let me start out by saying I think Arrma is a great company. I discovered Arrma in late 2012 seeing someone in college with one of their monster trucks. It could have been a Nero, but Im not sure. It was certainly large, larger than 1/10 scale for sure. Ever since I saw this truck, Arrma has been my favorite brand. I personally started out with the Kraton RTR Ver 2.0.
Ive owned more than 10 Arrma vehicles over the years, including the Kraton RTR 3.0, 4.0, the Kraton 8S, and most recently I got a 1/8 Kraton EXB (Ordered as soon as they came out). As you can probably guess, the Kraton is my favorite RC of all time. The Truggy layout, impressive handling, strong suspension, and great RTR ESC and Motor drew me to the platform. However, while I can definitely enjoy my Arrmas, I must admit that they can be very frustrating, and now days I even find myself wondering if I should just start considering another brand as my favorite. And now Im going to explain why I started this thread and why I am starting to loose faith in Arrma RC.
They break and have issues, often very expensive issues, far too often, and thats all there is to it really. I mean come on, I took out my Kraton 8S ONCE for 5 minutes and shattered both the front A-Arms on the third jump and in less than 5 minutes. Mind you, this was already the updated "Ver 1.5" with the split Tower-to-Tower Brace and rear chassis reinforcement plate. This occurred at a 1/8 scale outdoor track, on a mediocre sized jump, and the truck went at most 3 feet high off the ground. As it was brand new, I was driving the truck quite gently and had barely even touched 50% throttle. All I did was hit the brakes a bit too early in the air and the truck landed nose-heavy, I would say about a 20° nose-down angle, not a nose-dive by any means. You can probably imagine my dissapointment and frustration after this incident. Here I was, just having spent $1000 on this truck and it lasted all of 5 minutes.
Obviously I contacted Arrma regarding warranty, and they tried to say it was abuse and refused to replace them. As a result, it has sat on my shelf for 6 months now, only having been driven the one time, because I refuse to pay for the parts on a brand new truck. Also, I snapped a screw head off the center diff attempting to change the fluid, and now I need a whole new center diff for it because if I drill out the screw, I will damage the threads and render the case useless. All of this because Arrma doesn't know how to use locktite properly. I tried heating up the diff with my heat gun, no dice. I even tried resting my soldering iron tip on the screw head for so long that the entire diff got hot to the point where I could not hold it with my bare hand, and still broke the screw.
Now with my EXB, theres the obvious diff issue that so many owners have been experiencing. I shimmed my diffs, but it didn't help. The open rear diff broke with 0.75mm worth of shims underneath each sun gear. The outdrive shaft had ZERO play when pulling and pushing, and spun completely freely with almost no resistance whatsoever. I can promise you that my shimming was as perfect as it gets. The diff felt great too once assembled with fluid, yet the internals still wound up destroyed. Then, my center diff (which has LSD plates) was also destroyed, with the same perfect shimming applied. At this point in time, I have destroyed 3 EXB differentials, all having been checked and shimmed properly, and the truck has been built and running for maybe 6 weeks. That is simply rediculous. Im considering fixing it one final time and simply selling it at this point. I know Arrma has ceased production and is working out the issues but the fact this truck even got released in the first place tells me that Arrma never tested this truck properly before release, especially not on 6S power.
Arrma needs to just go back to standard diffs in the EXB. The LSD thing is dumb, it weakens the drivetrain overall and you can achieve LSD effect with thicker diff fluid. Its just a gimmick that compromises the integrity of the diff internals. Its a dumb idea and it needs to go away forever. It has done nothing but either ruin the handling of the truck because you can't predict how severe the limited slip action will be, or it has broken the sun gears time and time again because the tabs that hold the circular plate in place on the bottom of the sun gear are so thin, that when the diff lock activates and power is sent to those sun gears, they shear off almost immediately, see photo below.
I also had to modify the front end, removing the upper pivot ball spacer and grind down the lower A-Arm spacer and plastic underneath to eliminate the resulting extreme positive wheel camber, all to just bring the dogbones inward a mere 1.0mm so they wouldn't pop out of the front diff cups anymore. I also noticed there is simply WAY too much play in the bearings on an assembled diff. Take a look at yours and wiggle your bearings back and forth on the output drive hole. I used a Kyosho 96644 shim over the outdrive hole before the bearing, then assembled the diff, to determine that there is 0.20mm of wiggle/play in each bearing. This means that even if you shim the bearing from the outside using Tekno TKR1222, you need at least 4 shims to completely eliminate diff wobble, and still need to adjust from there to tighten the ring gear mesh with the input gear inside the bulkhead.
Now I have tirelessly worked for weeks to come up with solutions for my Arrma Trucks and I also believe I have discovered the reasoning behind such issues. As for the 8S Arms, I believe Arrma has not altered the composition of the plastics AT ALL from the 6S models, instead simply choosing to enlarge them in an effort to save money. As a result, the plastics on the 8S are far too brittle. As evidence , observe the photo below. You will see that the arm broke off so cleanly that it didn't even scratch the hinge pin, let alone bend or break it. This should be a clear indication as to just how brittle they actually are.
Now of course these are just a few of the issues with Arrma vehicles. I also own 3S and 4S Arrmas and if I were to write down every single issue, I could write a novel. So to shorten things up, below is a general list of ideas that apply to all Arrmas in specific categories to make them much stronger and easier to work with, and that will make them as strong, if not stronger than the competition. Because of my specific preference for the EXB, I have studied it and measured things especially and have more specific ideas regarding it. So lets get started with my suggestion for an Arrma 1/8 Kraton re-design:
Arrma 1/8 Kraton EXB Design Suggestions:
1.) MOST IMPORTANT: The Drivetrain of the EXB and in fact, the entire 3S, 4S, 6S, and 8S line-up of vehicles, needs to be redesigned an enlarged. I know you guys just redesigned the diffs for the EXB but unfortunately the design is still not even close to the strength of the competition. If you want a good emaple of a properly sized diff, take a look at the Traxxas 1/10 Maxx diffs. Keep in mind that these diffs were made for a truck that runs on 4S LiPo, and yet they dwarf the Arrma 6S diffs. However, I do not believe this rediculous size is entirely necessary for 3S or 4S vehicles. I have suggestions for all Arrma RCs but lets start with the Arrma 1/8 Kraton EXB.
Currently, the new EXB plastic diff cups are 29mm in diameter and roughly 20mm in length not including the outdrive hole. This is JUST the cup, NOT an entire diff assembly. I believe proper sizing for a 6S diff cup would be at or just under 40mm in diameter. In fact, the 38.50mm diameter of the new EXB Diff Ring gear would actually be quite perfect for a plastic diff cup. The length should go up from 20mm to 25mm or maybe even 30mm to acommodate larger internal gears. Of course, the thickness of the actual plastic material should be maybe 0.50mm thicker as well, as there have been several reports of overheating diffs and melting plastics. The overall volume of internal diff fluid should go up by at least 50%.
As for new gear design - the current EXB diff sun gears are 18mm in diameter. 22-24mm would be more appropriate considering the power of modern brushless systems. Similarly, planetary gears (A.K.A "Spider Gears") should increase in diameter from 12mm to about 14mm or 15mm. In all cases for all gears, be sure to increase tooth width and hight as well as engagement profile to suit the new sizes, plus increase the thickness of the gear bases to further boost durability.
2.) Diff Outdrive Cups as well as shims need to be redesigned. This would also apply to all other cups on the vehicle. The problem is less with diameter and more with material. We all see how quickly the dogbone pins eat into the diff cups and those cups end up needing to be replaced quite often. Use a stronger steel, one similar to Robinson Racing Xtra Hard Pinion Gears. The increase in diff outdrive shaft diameter from 5mm to 6mm from the RTR to the EXB is a welcome upgrade. The increase in retaining pin diameter from 2.25mm to 2.50mm is also a great change. As long as we can get stronger material for the cups, I believe the size of the EXB outdrives is large enough as is.
As for shims, the outer diameter is always too small on Arrmas. The outer diameter of a shim should always be just a bit smaller than the gear it is shimming. For example, on the current EXB, the stock smaller shims are 6mm ID x 12mm OD, while the OD of the sun gear is 18mm. Instead, these shims should be 6mm ID x 15 or 16mm OD for more Sun gear stability. Similarly, if Arrma increases the Sun Gear diameter to, say... 20mm, then they should use 6mm ID x 18mm OD shims. All shims should always have the same ID and OD to promote sun gear stability, while thickness can vary for proper adjustment. Arrma should also offer various shim sets to accomodate. The Kyosho 96644 shim set includes 10 x 0.1mm, 10 x 0.2mm, and 10 x 0.3mm shims in the kit for a total of 30 included shims. This is a great kit and Arrma should do the same with its Diff Sun Gear shim sets. So Ideally, for a 20mm Sun Gear, a package of 6mm ID x 18mm OD shims in 0.10mm, 0.15mm, and 0.20mm thicknesses (10 of each) would be perfect. And if Arrma is going to continue being lazy and not testing shimming before the truck leaves the factory, then one of these shim kits should be included with each Arrma RC free of charge.
3.) The EXB external diff gears (Crown/Ring and Pinion/Input) also need a boost. Yes, the new design for the EXB is a big improvement. The larger contact area is a huge upgrade, but I believe this needs to be taken a bit further even still. The current contact patch or tooth length is 5mm. A decent showing, but 6mm would be ideal. The Input/Pinion gear should be ever so slightly shorter with teeth that are 5.8 or 5.9mm long so that the input gear can be shimmed outwards towards the diff cup to get the thick end of the gear teeth fully engaged onto the ring/crown gear. If there is input gear teeth sticking out from the ring gear, it needs to be shimmed inwards. Additionally, each tooth should be just a tad bit thicker. In fact, the Ring and Input Gear teeth should be identical in thickness and strength as the Module 1.0 Center Diff Main Spur Gear Teeth. The same increase in contact patch/tooth length to 6mm would be appreciated for the Center Diff Main Spur Gear too. As for gear ratio, the current 4.3 Diff Input Gear turns to 1 Ring Turn is pretty perfect and allows us to run average-sized Pinion Gears in most cases. Same goes for the Center Main Diff Spur Gear. The current amount of teeth is pretty perfect. In fact, a larger diff size would raise the position of the Diff Input Gears and almost perfectly line them up with the center of the driveline anyways.
4.) Thicken up all the dogbones on ALL of the 6S vehicles including the EXB just a bit. Currently, the 6S dogbones are just a bit too prone to bending at their current 5mm diameter. 5.5mm diameter would likely be enough of an improvement. Also, adjust the lengths so that there isn't so much slop and movement in the cups.
5.) Get rid of the LSD diff design for reasons I discussed earlier. Also, get rid of the "Safe-D" Input Gear Shaft Cups, or enlarge the grub screw. The RTR cups are stronger and easier to work with because of the larger grub screw.
6.) Shorten the truck by just a bit, both in overall length and in the chassis and wheelbase. The thing is, bashing truggies do not need to be quite a long as actual race truggies. Shortening the truck has several advantages - the removal of material reduces the overall weight of the truck as well as reduces the possibility of bending longer parts such as the chassis and tower-to-tower brace. However, we do still want the Kraton to handle like a truggy, so I would say only a bit. Here are a few examples: Currently, the overall length of the EXB is 604mm. It should be entirely possible to bring this down to about 590-595mm. Meanwhile, the wheelbase should be brought down from 377 to 370mm and the chassis should also be shortened by about 5-10mm respectively.
See, the average basher won't even notice the difference in the length, its such a small amount that the truck will handle almost exactly the same, and yet there will be a noticable difference in durability and weight. Even when people build Kratons for racing, they never make it to professional levels. The Kraton is a basher and is far too heavy for anything more than casual club-level racing. Therefore, this slight shortening in the overall design would have nothing but positive results and no negative results.
7.) Beef up the 7075-T6 aluminum chassis and shock towers just a bit further. The move from 6061 to 7075 aluminum was a great move on Arrmas part, especially for the long and heavy Kraton. Its also a change that Arrma fans all over the world have been waiting for, for many years. However, people are still bending these parts ocassionally as their thickness isn't quite on par with competing truggies, although its very close. However, they don't need to be too much thicker to close the gap in durability at this point. I belive a 3.5-3.75mm thick 7075 chassis and 5.5mm 7075 shock towers would be more than strong enough. With this slight increase in thickness, the truck would be nearly indestructible. You could even then reduce the thickness and profile of the aluminum chassis braces a bit because the chassis and towers would be so incredibly strong that the truck would theoretically hold up to light bashing with no damage using no tower-to-tower brace whatsoever and possibly even plastic chassis braces. However, please keep the braces aluminum. The Tower-to-Tower brace is already prone to bending so leave its profile as-is.
These suggestions for the EXB can be applied to all 1/8 scale Arrma 6S vehicles but of course with necessary changes for each model. Now, lets move onto suggestions that apply to all Arrma models in general:
1.) Make every model into an EXB design. This includes ALL 3S, 4S, 6S, and 8S vehicles. "Mega" Brushed vehicles don't really need any redesigning. The Kraton EXB renders all current Arrma RTRs completely worthless and obsolete. If you want to sell RTRs, then throw RTR electronics into EXB models and sell those instead of RTR plastics and aluminum. Offer an EXB model of every car (offroad at least) and they will sell like hotcakes (or at least they will when the drivetrain actually holds up). Continue offering rolling chassis as an option and extend that to the entire range of cars. Being able to choose your own electonics is a massive advantage for Arrma since almost every hobbyist upgrades their electonics at some point anyways.
2.) For the 3S and 4S models, its time for metal diff gears. The plastic composite gears just aren't good enough for 3S+ brushless power. In fact, the current 29mm EXB diff design would be perfect for all of the 3S and 4S 1/10 scale models. This gives you a way to repurpose the new EXB diffs so that they do not go to waste, provided that you get rid of the defective LSD system in favor of standard, flat-bottomed Sun Gears and traditional diff design. The current plastic diff gears found in the 3S and 4S models can be used for brushed "Mega" models. As for 8S models, the diffs can be increased in size similar to my suggestions for the EXB and 6S models. However, the increase in diff size may not need to be as drastic for the 8S vehicles since the diffs are already quite large.
3.) For 3S, 4S, and 6S vehicles, ever-so slightly softer plastics would be a great upgrade. EXB plastics do NOT need to be any thicker, just slightly softer so that they flex rather than snap under heavy stress, quite like RPM parts. As for 8S vehicles, the plastics need to be softened much more drastically. After my experience with the Kraton 8S, its clear that the A-Arms are pretty much entirely worthless as it currently stands.
4.) IN GENERAL, Stop using so much locktite on your screws! Please Arrma, understand that locktite is simply used to stop a screw from vibrating out of metal threads, thats IT! Threadlock is NOT intended to reinforce screws or threads AT ALL. All you need is standard, watery blue loctite, such as Vibra-Tite 121, applied to 4-5 threads of a given screw in a LIGHT coat to secure it. That goes for ALL metal thread screws regardless of design or part its holding together. When I tried to pull apart my K8S center diff, the screw broke due to the rediculous amount of super-thick blue locktite that was used. Each screw was entirely coated top to bottom with a VERY THICK coating. There was so much powder left behind that it filled the screw holes as I pulled the screws out. Thats just rediculous. The ONLY exception to using Vibra-Tite 121 and in very small quantities, is cup and pinion grub screws. In this case, a medium-high strength and high-temperature specialty blue locktite such as Vibra-Tite 123. It is more than strong enough. Ive NEVER lost a pinion gear while using it on the grub screw so long as I give it 24 hours to properly cure. There is NEVER, EVER a nedd for red locktite, EVER! Red locktite always does more damage than good, constantly causing the stripping of screw heads.
5.) The New Kraton EXB comes with a heavy-bash-ready front bumper/skid plate design. Arrma should also but this design in the rear of the EXB. It makes no sense to have the front end so well protected but then the rear is left wide open to damage. These bumper/skid plates should be added to every single Arrma no matter how large or small or the power system. Every basher crashes his/her truck sooner or later. Its enevitable, so protection is a high priority.
6.) Similar to the Kraton EXB, the Big Rock 3S should also be shortened ever so slightly in the persuit of less weight and better durability. Same goes for the Kraton 8S and 4S as well as any other long vehicles.
7.) Get rid of the Spectrum STX-2 radio system entirely from ALL models. Its a terrible radio. Include some other radio instead on RTR vehicles.
8.) Include better servos on RTR models. The current servos are okay but come up a bit short. Increase 1/10 models from 7KG to 12KG, and 1/8 models from 15KG to 20KG. This should be plenty enough to satisfy owners for quite some time.
9.) Offer a wheelie bar for those who desire a less extreme wheelie angle.
Well, thats my list of suggestions. Fellow enthusiasts, please tell me what you think of this. Remember that the more you comment and share, the more likely that Arrma will take this list seriously. Arrma, it is fully understood by both myself and others that an increase in price will be necessary to make this happen as well as the fact that it could take years to implement, especially if you are updating all the vehicles. When it comes to pricing, just try not to let it get too rediculous. For example, the 1/10 Traxxas Maxx costing the same $550 as an RTR 4.0 1/8 Arrma Kraton is a pretty rediculous prospect. That being said, I would be more than willing to pay $550 for a 1/8 Kraton EXB roller if it had ALL of my redesign suggestions on it; and if it did NOT break straight away out of the box. If it held up like a Maxx does, It would be more than worth the price.
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