Jump to content
wtcc5

wtcc5s Tamiya MadCap overk*ll build

Recommended Posts

I’m glad you asked.  Check out the original 1989 Astute kit parts with unique adjusters on 4mm threaded shaft.  I know this arrangement will direct fit, work with your hubs and reduce the torque reaction through the arm on power.  Note that both Madcap and Astute with the soft arms both have the upper arm pivot on a shaft, preventing the whole assembly from twisting. The Super Astute arms are much harder which allows the conventional ball ends and adjuster.  I’ll link one of my posts that is similar as a close reference but I think both Astute adjuster ends for the Xtra Speed hubs.  

  • Like 4

Share this post


Link to post
Share on other sites
On 5/7/2024 at 3:39 PM, Thommo said:

 

 

IMG_2684.JPG

 

This is a variation using trimmed Madcap rear hubs, same principal. Earlier in my thread you can see where I used Madcap rear arms and a ball nut on the outer adjuster which was a half measure improvement.

  • Like 4

Share this post


Link to post
Share on other sites

@Thommo: That is great! Thanks for sharing your wisdom! This design is brilliant but not simple with the added angled metal sheet and additional turnbuckle. I didn’t know it up to now.

  • Like 3

Share this post


Link to post
Share on other sites

Guess @Thommo meant the Madcap solution is sufficient for you. The additional rod on the Astute was for adjusting the toe in angle of the special Astute rear hubs.

  • Like 1

Share this post


Link to post
Share on other sites

I had some similar inboard pivots made for my buggies with the blue thundershot arms to help the flexy arms whilst still getting camber links. Works well and super easy to design for you Kevin.

  • Like 3
  • Thanks 1

Share this post


Link to post
Share on other sites
7 hours ago, wtcc5 said:

@Thommo: That is great! Thanks for sharing your wisdom! This design is brilliant but not simple with the added angled metal sheet and additional turnbuckle. I didn’t know it up to now.

Yes, the upper arm hinging on shafts gives integrity to the whole assembly.  Replacing the hinge with a ball nut on one end or both ends allows the hub to rotate as the lower arm twists.  Astute B3 / B5 parts are rare but they are never cracked or broken.

3 hours ago, ruebiracer said:

Guess @Thommo meant the Madcap solution is sufficient for you. The additional rod on the Astute was for adjusting the toe in angle of the special Astute rear hubs.

Sufficient but the OG Madcap upper arms are the same soft plastic, so still have some twist.   

1 hour ago, ThunderDragonCy said:

I had some similar inboard pivots made for my buggies with the blue thundershot arms to help the flexy arms whilst still getting camber links. Works well and super easy to design for you Kevin.

Brilliant !  The torque twist is easy to demonstrate but difficult to explain...  Have a look at those B3 / B5 parts, clearance with the rear dampers and the gear cover on the right side are critical.

  • Like 3
  • Thanks 2

Share this post


Link to post
Share on other sites

At the moment I cannot believe my 3D-print could handle the forces of the torque twist, especially if I bottle a jump. My brain favors a second link at the moment, which will connect hub and chassis respectively a extension of the body mount plate...

 

I ordered more Xtra Speed parts, electronics for this project and two steering sets to test and/or combine:

IMG-7453.jpg

 

In the last evenings I drew a new top deck design in CAD to see how it all evolves:

Bildschirmfoto-2025-02-07-um-17-02-22.pn

 

Overall it seems to be ok. But two new worries were created:

  1. Where can I get a 160mm turnbuckle to connect servo and steering?
  2. This steering assembly builds a bit high and will rub on the front part of the body.

 

  • Like 2

Share this post


Link to post
Share on other sites

Get a 3mm titanium rod from ebay and let cut a thread on it. Steel will be unneccesary heavy. Also you can try 1mm steel wire and bend it, simular like used on airplanes.


The Predator has a funny long steering rod as well.

i2XVvWFZSLeZ9-jK67ZN2Mp94fO5MP8mhyph_nSx

 

Btw. did you made a 3D scan of the cassis cup? Looks like you had a mesh converted to a solid.

  • Like 1

Share this post


Link to post
Share on other sites
2 hours ago, Collin said:

Btw. did you made a 3D scan of the cassis cup? Looks like you had a mesh converted to a solid.

No, another wizard build that and uploaded it to Thingiverse :)

Share this post


Link to post
Share on other sites

Fabulous @wtcc5 work as always! Out of interest, what's the rationale for sticking with the Madcap plastic chassis over an Astute sheet GRP/CF one? Wouldn't that solve these problems? That'd comply with any racing rules wouldn't it? 

  • Thanks 1

Share this post


Link to post
Share on other sites
1 hour ago, BuggyDad said:

Fabulous @wtcc5 work as always! Out of interest, what's the rationale for sticking with the Madcap plastic chassis over an Astute sheet GRP/CF one? Wouldn't that solve these problems? That'd comply with any racing rules wouldn't it? 

Tamico Offroad cup doesn't allow FRP or carbon chassis, only plastic tub. I guess that's the explaination :)

  • Like 3

Share this post


Link to post
Share on other sites

Not sure I‘d go for that long distance between steering and servo. 
any kind of flex in the chassis might effect the steering, 

  • Like 2

Share this post


Link to post
Share on other sites
25 minutes ago, Gratuit said:

Tamico Offroad cup doesn't allow FRP or carbon chassis, only plastic tub. I guess that's the explaination :)

That'll be it then! 😂

Share this post


Link to post
Share on other sites
1 hour ago, bsy2010 said:

Not sure I‘d go for that long distance between steering and servo. 
any kind of flex in the chassis might effect the steering, 

That´s a good point Bertin! That has to be kept in mind. Nevertheless I like this solution a lot, as it doesn´t bring the need up to cut the chassis. As the steering link is in the center line and steering links as well as the servo is directly linked to the stiffening plate, the effect should be minimal I guess, when the chassis is twisting. If it will try to bend front to rear, e.g. landing a jump, there could be a steering effect. So I´d goe for a 2,5mm carbon plate as stiffener. This and the chassis should ensure a trustable steering. But that´s my personal impression from looking at it.

The steering link could also be done as a small carbon rod with inserts for a shorter turnbuckle. Or a varbon plate with one end screwed with a flanged bearing directly to the steering link, and only one end connected to a servo post of aluminum screwd to a short turnbuckle. Still many options.;)

  • Like 2

Share this post


Link to post
Share on other sites

Regarding the battery, is the saddle pack  form factor still a thing? It looks like it would provide the most flexibility in its layout.

Share this post


Link to post
Share on other sites
5 hours ago, ruebiracer said:

The steering link could also be done as a small carbon rod with inserts for a shorter turnbuckle.

This is a good point. I have some carbon tube that can be tapped for M3 and has about a 5mm OD I think. I imagine it would be a very light option and bending not an issue, and it was cheap on ebay or similar. 

  • Like 2

Share this post


Link to post
Share on other sites

@BuggyDad: Can you guide me to this carbon tube please. I once wanted to do something similar, but the tube just couldn't handle pressure...

@ruebiracer: Thanks for all your input so far! I think the carbon rod will be the solution. for that problem.

 

I continued with my CAD work. Now focussing on the shock towers and support plates. Overall the project grows a lot now:

Bildschirmfoto-2025-02-09-um-12-43-41.pn

 

In front the shock tower didn't change much regarding the dimensions:

Bildschirmfoto-2025-02-09-um-12-50-20.pn

Bildschirmfoto-2025-02-09-um-12-37-41.pn

The changes are the thickness of the material growing from 2.5mm to 4mm. On the backside I added pockets for the 5.5mm nuts to make wrenching easier. The inner section is now marginally wider, because the MadCap body is a bit too wide for the standard Astute shock tower. This design gets rid of the front plastic body mount and integrates it in the design (I know this from another buggy, but cannot recall the name of it :rolleyes:).

 

The top deck was optimized. It has a better connection to the rear section and received two more attachment points right behind the steering. Complex shims were drawn to key with the chassis and connect the slip-on-style top deck strong with the tub chassis:

Bildschirmfoto-2025-02-09-um-12-39-30.pn

Bildschirmfoto-2025-02-09-um-12-38-44.pn

 

The rear support plate underneath the rear shock tower grew a lot in size. It will act as connector to the top deck and also grabs two more screw holes in the tub chassis. The width increase comes from the additional mounting points for the rear suspension. Overall, I looked how much space is left between support plate and the other components and then filled this space ^_^

Bildschirmfoto-2025-02-09-um-12-36-41.pn

Bildschirmfoto-2025-02-09-um-12-37-17.pn

Again pockets were implemented. This time these are for the aluminum body posts. Take a closer look to the middle recess. There the servo arm will find space on full throw.

 

Let's stay at the rear. This picture gives a good look into the electronic compartment. The servo is mounted to the top deck and sits as low as possible. I wasn't aware of the steering rod carbon tube solution yesterday and just had my negative experience, so I opted for a plate design combined with Xrays small servo posts:

Bildschirmfoto-2025-02-09-um-12-35-38.pn

 

The rear shock tower looks slightly different than the stock design, but mostly sports the same dimensions. Its changes are the lower recess (again for the servo arm movement) and the upper edge line. The latter changed, because I don't need the upper mounting points. The middle upper holes for the wing mount changed. They are on the same row as the lower three holes and like this allow to use plastic wing mounts instead of the wire:

Bildschirmfoto-2025-02-09-um-13-11-05.pn


Bildschirmfoto-2025-02-09-um-13-11-31.pn

For the upper shock mounts pocket were drawn to have the shocks as vertical as possible in the car and still have a thick strong shock tower.

 

With this the main work is pretty much done. I still have two topics in mind to strengthen the lower rear of the chassis and want to reduce the flex of the front arm (within the rules of course :P).

Test prints will be made next week.

  • Like 5

Share this post


Link to post
Share on other sites
16 minutes ago, wtcc5 said:

@BuggyDad: Can you guide me to this carbon tube please. I once wanted to do something similar, but the tube just couldn't handle pressure...

The one I bought is here. 

https://www.ebay.co.uk/itm/404738505446

I do now realise that I have not used it on a runner yet, so I can't confirm it'd handle the pressure. Mine is intended as a Boomerang front shock tower brace, which also needs to hold quite securely to M3 threads either end. 

I like your shock tower ideas - I too intend to combine a Madcap shell with an Astute front tower and will CNC my own tower. Your integrated body mount is Kyosho reminiscent. 

Share this post


Link to post
Share on other sites

Great designing and keeping everything in mind Kevin! :) 4mm for the shock towers is maybe a bit too much for my (personal) liking, would have sticked to 3mm max., but with the Aluminum bulkhead it´s probybly o.k. . I always would keep a little flex/soft spot in the car, as a shock tower is easier to replace than a cracked Bulkhead or chassis.:lol: But that´s my only critic on the fantastic design work.

For the carbon tube: Maybe threading is not needed, you can glue 2 Threads insinde the tube with e.g. UHU Endfest and bake it in the stove. That´s the principle, how the guys do carbon main shafts on the cardan cars like TBEvo 6 and so on. Think of the famous E-whippler shaft. Ultra light and strong. <If it van withstand the torque, it should also work as steering rod. If you are afraid, start testing with a servo saver to cut the peak loads. But probably, that would be the lightest and easiest solution.:ph34r:

This is the glue also used by bicycle guys:

UHU PLUS ENDFEST 300, Tube Binder, Tube Härter 33g | UHU plus Klebstoffe | 2-Komponenten Klebstoffe | Klebstoffe | UHU-profishop - Klebstoffe für gewerblichen Bedarf

Especially by heating the parts, this glue can go to the tiniest holes and is sticking even better.

 

  • Like 1

Share this post


Link to post
Share on other sites

Whats not fully clear to me, is how you want to link the hub to the anti-twist link. :) Do you get full suspension travel without blocking the movement? Totally interesting, and I know, that you have a plan. :lol:

  • Like 1
  • Haha 1

Share this post


Link to post
Share on other sites
On 2/8/2025 at 5:35 PM, Honza said:

Regarding the battery, is the saddle pack  form factor still a thing? It looks like it would provide the most flexibility in its layout.

Sorry, I forgot to answer: Saddle packs are history as far as I know. I also haven’t found a shop to get regular ones in Germany. Still, your suggestion was good. Thanks for it!

Share this post


Link to post
Share on other sites

Can’t trust anyone, but yourself :(

IMG-7483.jpg

The distances between the holes of the chassis-file are off by several millimeters. Good, that I made a test print…

  • Like 1
  • Sad 1

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

×
×
  • Create New...