MF-01M - A mid motor 4WD rally M-chassis

[Honza]

I skipped the last race due to weather, so first race of the V2 was this weekend. And it was quite successful. Well, except for another broken front arm. Luckily I have printed couple of spares. I got TL-01 hinge pins for the future interation, which should help to hold the printed parts together .

I know I should've used firmer dampers on this surface, but I love how it leans into corner 😃

[JimBear]

5 minutes ago, Honza said:

I know I should've used firmer dampers on this surface, but I love how it leans into corner 😃

Almost Citröen 2CV style, there!

 

[Honza]

5 minutes ago, JimBear said:

Almost Citröen 2CV style, there!

Yep, that's what happens when you run dirt settings on a higher grip surface 😃 I run stabilisers on my main car, but that's not an option here (yet? 😁)

[Honza]

Missed another race this weekend due to illness... But at least I finally got into uploading all modifications I'm using on my chassis.

Here's my Printables collection that contains them:

https://www.printables.com/@HonzaP_226225/collections/125847

[CRC505]

This design is really great, I want to make one too

[Honza]

1 hour ago, CRC505 said:

This design is really great, I want to make one too

Thanks! Go ahead and share your build here, it's always great to see another build

[Honza]

Another race This time, the Mazda wasn't the only m-chassis on the start

Finally got to finish my own mini rally tires. They are old, slightly worn clones of Tamiya tires made of softer compound - they work much better than Tamiya's own tires.

Another, not pictured, modification is installation of stainless steel hinge pins - although it didn't help with front arms breaking, it at least held them together to get over the finish line.

I also involuntarily tested water resistance of THW-1060 😁 

 

 

[Honza]

From the series "why Tamiya haven't thought of that?", I finally tried whether I can run a single propshaft for multiple wheelbases, since my design allows for the propshaft to stick out of the bevel housing - this is an L propshaft on M wheelbase. In the same way, M-propshaft could be used for the shortest wheelbase. 

[Honza]

The last race resulted in DNF in the last SS due to driver's error. Good news is that the suspension mount worked as anticipated and it didn't break other parts of the chassis.

Over the summer break, I'm planning some modifications. I'm waiting for delivery of #51748 parts tree to test some new ideas..

[Honza]

One #51748 set on its way, so in the meantime, I tested an idea to use 33mm CVDs with them. I thought that I'd need 4mm hexes to compensate for longer swingshafts, but turns out, that it's not needed. Wheel axles used on XM-01 are shorter just by those 3mm.

This means that I'll be able to make slightly longer front arms. With starting length of 20mm, each milimeter counts.

[Honza]

Still need some more parts, but looks like XM-01 uprights will work:

With same width and lower damper mount in the same position as stock, arm was extended by 6mm and it achieved same lever ratio as rear arm, so it should provide nice linear damping. I plan to add downstops and move the damper mount down, together with custom damper stay in the future.

So far, it is assembled on a spare chassis. Since MF-01X mounts ball joints from the bottom of the upright, I had to cut part of it.

Btw have you ever wondered why bearings stick out of M-07/XM-01 uproghts? It's because older M-chassis use 6mm hexes and that's depth of hex inside the wheel. Newer chassis use 5mm hexes, which wouldn't fit.. But with bearing sticking out, it clears the wheel easily.

[Honza]

First race of the season is slowly approaching, so I did some modifications on my MF-01. 

Since the last post, I finished the new front suspension and it worked quite well, but it used the same short shocks as the stock arms. Luckily, the longer arms allowed me to mount the shocks lower and more upright, clearing the stock shock tower, so now I can use the same 60mm YR shocks as the rear axle.

The other modification was redesign of the bumper. The original design could interfere with tires in muddy conditions, so I had to redesign it to get a bit more clearance. The new design uses TT01 foam, which is thinner than one I used previously, so I got a bit more ground clearance.

[Honza]

(Our) first race of the season. Because my primary car failed right before the race, I got to race MF-01X. While I've driven it for some short time, I never actually got to race it on a track. Holy cr** it was great! Obviously, soft suspension wasn't the best thing on high(ish) grip, but I was really happy with the car, it was stable, with great reaction to throttle and surprisingly fast for a brushed setup. I really enjoyed driving it, so I'm pretty sure about one thing: I'm building another one for myself! 😁

[Honza]

A fellow racer asked me to print another conversion kit. So now there are two mid motor MF-01Xs racing against each other.

Of course, it wouldn't be a proper race if there weren't any issues. Last year, after series of crashes that broke the rear suspension mount, I printed one out of PCTG, which is much more impact resistant than the original petg part. Well, it worked a bit too well and another crash broke the chassis instead of the mount. Good thing is, that the suspension mount served its secondary function and hold the car together, even though the crack caused inconsistencies due to geometry change. After I glued it with CA glue, it held together until the end of the race. But it's another thing that needs to be addressed in the V2.2 I'm currently working on.