Honza

Some progress on the gearbox, so I can reveal the second big change to XV-01 - in order to clear the motor, the belt would have to be lifted by a centimeter or so - which is not impossible, since the bottom of the belt is the slack side with the motor in the back - but I didn't like the idea. So I chose a different approach. This is why I needed the second idler that rotates in the opposite direction The shock tower mount is designed for stock rear tower.

@ChrisRx718 This is weird, I tried to do some math and arrived to similar numbers as the article. 2-3mm gap doesn't sound right, since the two teeth difference does 0.4mm difference in gear radius. BTW, when I checked MB-01 manual, I noticed that the stock mount is marked "20/22/24" on the bottom - I guess that's for the 70T spur that'll be used in BT-01 - and also aligns with E/G/J positions on TT-02.

@ThunderDragonCy Hint: take a look at MF-01X 🙂 I thought that not fully revealing my plans would lead to an interesting discussion and might lead to new ideas Like your comment, I didn't even realize that I made a 4-gear modification 😁 Once I get the model to presentable state, I'll show it 🙂

Isn't this combination a bit too tight? 29T/65T position on MB-01 should be equivalent of "J" position on TT-02 mount (26T/68T), for which the article you refer to, suggests 46T/96T combination. It's quite weird that the metal mount doesn't come with slots to mount the motor. That would make the gearing selection much easier. I'll be watching this build. Isn't it fun working around limitations of Tamiya's design? 😁

Almost, this will be an option if the other solution doesn't work. That's the reason why both idlers are on the same level. Embie chassis is meant for full scale variant. The mini variant will use custom chassis - the exact design is still something I have to decide, but I'm thinking about similar concept to my rally chassis prototype - aluminium "backbone" with 3D printed side guards to create the bathtub. The plan is to have a shorty transverse battery, similar to MF-01X. Another option would be longitudinal position, but slightly shifted to the side to make space for the servo and electronics next to it. There's no belt or driveshaft in the way, so there's a lot of freedom in electronics layout. The opposite spinning direction is actually necessary for what I want to do. I added only one idler, in combination with lowered motor plate/spur layshaft, it moved the motor quite far in the front direction, which is why it might appear that I added two idlers.

Thank you for your support Correct, this is the rear gearbox The front will remain stock, just flipped around. I was thinking about front-mid position, but that would be too complex, if not impossible. This variant should fit Embie's conversion chassis after some adjustments. The motor mount is re-used from the stock chassis. I try to use stock parts wherever possible to make my designs more accessible. now, can you guess the other change to XV-01 design? 😁

So this is a project I've been working on for a while, although I got distracted by other project lately, so it's still in very early stage. Anyway, inspired by @wtcc5's thread, I decided to make a parallel topic that follows development of a different kind of a 4WD mini chassis Hopefuly I'll be able to finish it. The idea for this chassis was born at the end of the last year - I wanted to make something more advanced than my MF-01X. The main inspiration is differential in M-07/8, which is the same as XV-01, and long suspension arm design in M07/8, which works much better for rally than the older M05Ra one. I thought that I could use top halves of XV-01 gearboxes with custom bottom halves, which would serve as mounting points for M-07 suspension arms. Well, that didn't work and I had to change the motor position using custom top portion of the gearbox. And just when It started to look interesting, Tamiya decided to announce the XM-01... I was thinking about ending the project... but realized, that thre's still a point in continuing - XM-01 will allow me to skip design of the bottom gearbox part thanks to the new suspension design, and I can focus on making my designs compatible with a full scale XV-01. Full scale XV-01? Yes, my plan is much bigger than just shrinking XV-01, that's just one of the three big changes to the XV-01's design. Can you guess the other two? This picture might provide a little hint: It is nearly finished design of the gearbox. I needed to get the motor lower, unfortunately doing that with the stock gearbox would limit the available gear ratios. So I added another idler, which allowed me to reuse the stock motor mount. You can see that it created another issue, but in fact, it's not an issue at all. Can you guess why?

Yes, it's common, but DS is quite extreme example, because the original has 3,1m WB, 1,8m width (with 1,5m track), but rear track width only 1,3m... It's nearly impossible to stretch that to a standard RC chassis. Even MB-01 stretched to 257mm wouldn't fit DS proportions, but it would be atleast a little closer.

Looking forward to this What drivetrain cases/bulkheads are you going to use, custom? MB-01? Or AM-1? I like it's drivetrain as well, and it seems, that they can drop into whatever belt-driven chassis bulkheads one wants.

M08 can run on dirt, too And with XM-01 release, there will be "Ra-type" suspension available.

@ThunderDragonCy TRF201/FF-03 uses layout I have in mind, with the same 20T/48p gear. This just takes a 4mm rod and drill to make a custom layshaft. It's just backup idea if you're not successful in sourcing the TD4 shaft. It's been even possible to get a 20T/48p steel counter gear, before all manufacturers started making layshaft/counter gear in one piece.

Awesome project. Tamiya based/inspired custom chassis builds are becoming quite common lately 😁 Regarding this What about using a counter gear from a buggy that uses a cross pin to secure it to the shaft? Then you could make a custom layshaft with exact parameters you need.

CC-02 uses #19803212, which I assume could work for front?

Last few adjustments and I think that the car is ready for the next season. I just need to finish the other two DIY rally block tires and test if they stay in one piece 😁 Since I switched to a different RC unit with a more compact receiver, I could design a new chassis extension piece that could fit the receiver inside. It looks much better without all the wires running to the rear I'm still not happy with the front suspension. Custom "banana" curved arms with damper pivot moved closer to the inner hinge pin helped to get softer damper action, but also resulted in non-linear spring rate with long front dampers due to their more upright position. So I returned to old black Tamiya dampers, which could fit into original damper mounts, with YR piston shaft to gain 2mm of length. Thanks to custom arms, they have just enough active length to cover whole suspension travel. (Picture that compares two types of damper didn't upload) I also designed a new bumper prototype, which should be stronger against hit from the bottom and act a bit as a skid plate. I also found a piece of black foam, which I thought would look better than the white foam I used before. I'm thinking about getting TT-01 foam, which comes in variety of sizes and is 5mm thinner, which would gain some ride height. (Photo showing bottom of the bumper didn't upload) Once I finalise the design, it'll be printed out of the same black plastic as front arms, which has slightly better impact resistance than the red PETG. And photo of the complete chassis, before a little teaser - I went through parts left from the previous builds and realised, that I'm not that far from completing another MF-01X... Or should I say TL-02? 😁 Btw, I also checked the weight - without the body, the car weights 1390g, with 48/52 F/R split. My target was slightly above 50% for the front axle, so it's not that far off.. and vast improvement over the stock

Corrected, thanks 😁 yes, 42mm was meant for XV-01

This description says that that it has about 13mm ride height at high settings. The length of the driveshafts is limited by the differential, XV-02 type is wider than XV-01 type, which is used in M07. It'd be probably better, if they based the rally chassis around XV-01.

So if I understand it right, it comes with two rear gearboxes, one for 225/240 and one for 210mm? That's great, although the longer gearbox is quite big chunk of plastic 😃 XV-02 has 37mm driveshafts Vs 42mm on XV-01. So XM will use its own 28mm, or it'll be slightly wider to reuse 30mm shafts from m05.

First batch of parts for my TB03 build. Still a bunch is missing.

@Tamiyastef yes, on Facebook.

Yep, it's 210mm, the cad picture in the first post shows 225mm Definitely. The front axle is also quite close to the bathtub - so 1.9 wheels for Jimny or Mercedes might not fit

Only 4 of the 8 holes on the brace are used. So it can extend to 225mm by switching the outer holes and then to 239 by switching the inner ones (or vice versa) There's also photo of the bottom of the chassis posted by Tamico I wonder if they are going to use inserts and long bolts there? I'd like to see disassembled chassis. So far, it seems that the rear gearbox is quite compact and two of them could be used to make a custom chassis

It supports all three wheelbases, including 239mm used for Golf

I noticed that the XM-01 uprights are quite similar to M-07.. Who is going to built an M-07Ra? 😁

Well, it depends on how much modified the touring car is, even TRF can become a dedicated rally car 😀 (Car and photo by RC Modely Střihoun) This build, XVs, XM and MST-XXX rally have one thing in common - front weight bias, which helps with steering on loose surface. Simply lifting a touring car doesn't make it a dedicated rally car

2CV has 2400mm wheelbase, DS 3100mm. DS is almost 1m longer overall.