4WD + 4WS Blitzer Beetle

[Frankster 2073]

Started when tried to look for a Blitzer Beetle but due to the pandemic there was a shortage of kits available.   Next I found a Sand Scorcher body and started to think 🤔.    I pulled my Monster Beetle body off and placed it on my son’s TT-02B Plasma Edge II.  Overall it appears to fit but is tight.   Also knowing my son’s TT-02B a lot of upgrades are required and I have been slowly amassing upgrades / hopups.  
 

Next I discovered Tamiya Club and realized I am not the only person with the same idea 🤗.  A lot of great projects by others and here is my interpretation.

I took a day off work and here starts my 4WD  Blitzer Beetle build.

EDIT: now with 4 wheel steering 

EDIT again: Completed (Oct 18, 2022)

[Frankster 2073]

I have many hop-ups / upgrades but tried to keep it simple and purely functional.   No alum battery holder here but mostly drive train related.  Interesting that I did not invest into metal gears and diff….  I want to see how the plastic gears last… for science!

One interesting part is ordering 2 rear FRP towers as the rear is symmetrical.  I noticed this on my kids car and there are a few YouTubers who did the same.  Along with this is 90mm dampers, but I prob should have ordered 100mm+ dampers for more ground clearance.

[Frankster 2073]

Chassis

Typical TT-02B chassis so I will not spend too much time writing up this section.  I did see others add washer / shims to the diff to get rid of slop. Also used anti-wear as it is a thicker grease 

My first time time installing a brushless.

Chassis 60% completed
With beetles hard shell the front and rear shock towers do not fit.   Looked at options to shorten wheelbase to better fit beetle body.  In the end I reversed the rear arms and it works.  See end result in Damper section.

[Frankster 2073]

Dampers

90mm dampers from Xtra Speed.  First time picking up generic dampers and realized there is no oil pre-filled inside.  Had to pick up a bottle and add damper oil.

Installed with FRP rear damper towers at front and rear of car. Had to make a few adjustments to make it work. 
Rear tower is on an angle and the damper movement is not smooth.  Cannot tell if it is the cheap dampers or the angle of the pivot.  Will need a deeper dive into this problem

[Frankster 2073]

Testing the Body

Body is tight fit sitting on shock towers

wheelbase has been shortened 266mm to 252mm+\-

Proper Blitzer Beetle wheels.  4 rear wheels + 4 rear tires.  i had to shorten the damper spacer on the front tower which gave a little more wiggle room.

 

I need to pick up a servo mount as the one which came with the kit I used in my Manta Ray.  
the shorter stubby wheelbase looks great

[Frankster 2073]

Body 

Better photos in the daylight

added the TT-02 dust cover.  This will give the tub chassis more girth as it looks thin and you can see day light between the body and chassis.  Will paint it black / smoke

Tested chassis with my completed Monster Beetle body. May end up making it interchangeable.  Options include:

1) drilling holes into sand scorcher body side to accept side mount

2) buy new blitzer body with factory hole mount to work with monster beetle chassis and new 4WD Blitzer beetle chassis

 

[Frankster 2073]

Looking at the rear suspension, has anyone tried to make this 4 wheel steering?   Get a second set of front arms in the back?

[Ziddan 984]

Hey, just noticed that you rear arms are backwards in the pics with the shocks fitted, they are supposed to sit to the rear, thats why you are having them at an odd angle.

As for all wheel steering, the front and back are symmetrical so as long as you get servo+steering linkages to fit it should be possible, an option might be to put a servo upside down with the pinion towards the back, mounted to the shock tower, put the wide multi hole servo saver pointing forward on it and run links from it to the wheels. it would be higher tho so i think it would induce some bump steer/toe out.

 

[Frankster 2073]

1 hour ago, Ziddan said:

Hey, just noticed that you rear arms are backwards in the pics with the shocks fitted, they are supposed to sit to the rear, thats why you are having them at an odd angle.

As for all wheel steering, the front and back are symmetrical so as long as you get servo+steering linkages to fit it should be possible, an option might be to put a servo upside down with the pinion towards the back, mounted to the shock tower, put the wide multi hole servo saver pointing forward on it and run links from it to the wheels. it would be higher tho so i think it would induce some bump steer/toe out.

 

Rear arms are reversed on purpose to shorten the wheelbase to better align with the body.  Yes the dampers are on a strange angle.  They appear to be working more smoothly after a manual break in.

Any hand sketch?   I have an idea in my mind but open to other suggestions.  Overall I am more inclined to a dedicated rear servo to avoid bump steer

[Ziddan 984]

Cant draw but here are three option that come to mind, the first one with the arrow is to as far back as it could sit and a little lower, got stuff in the way on mine.
The servo could mount via the body post holes and possibly be braced to the shock tower.
Another option here would be rolling the servo towards the camera so it might be mounted in the body post holes and an extension from the rear battery post.

2nd shows another option that could use the body post holes and be mounted to the rear tower more closely.

All options would then have the wider servo saver to allow mounting two ball ends that would go to the steering.

Yet another might be putting the steering behind the shock tower but that would leave it quite exposed to getting hit so that option doesnt seem great to me.

[Frankster 2073]

4wd Blitzer Beetle now has rear wheel steering.   Overall I picked up front suspension assembly and installed in the rear.  Added 3 washes on each side to make up for the shorter lower arm length.  
Now trying to figure out how to fix the steering to a second servo.  At the moment it appear the servo will be behind the rear shock tower. 

[Kol__ 3387]

Great build @Frankster! Looks like this will be a unique beast once it's ready to hit the trails mate

[Frankster 2073]

Rear Steering problem

Tried to keep it simple with a servo horn and direct linkage similar to many 2WD buggy front suspension  (DT-03).   Zip tied the servo to see if it would work.  In the end, the bump steer was too much for my liking.   The wheels would steer when suspension is at compression.

sorry not sure why the photos are upside down.  Suspension compressed vs regular state 


In this last test, the steering angle is different for each rear wheel in this set up.  Overall steering rods need to be parallel to the axel and the steering linkage needs to the at same point as A arm pivot

 

Next step is to figure out the steering articulation before I mount the servo.

[Frankster 2073]

Reversed the the hubs in the rear. Approach is instead of copying the rear suspension I am mirroring it.  Downside is a large motor and spur gear so the steering will need to be elevated. 
stuck on steering assembly with blue tack to visualize.   Steering and dampers just clear each other.

Learning from past issue for the bump steer, I tried to make the angle of the steering rod align with the A arms.  This produces a tall pivot ball joint with hub and would be a weak point

Back to the drawing board 🤦‍♂️

[Ziddan 984]

What about reversing the hubs again, rolling the sterring setup 90 degress backwards and putting it vertically on the backside on the shock tower with the servo on the  front?

Also copying and reposting what i wrote in another thread:

Quote

 

Another option could possibly be a pinion on the servo and a rack that goes nearly the full width of the chassi to keep the pivots of the steering rods closer to the pivots of the arms.

Something like this.

 

Servo upside down on the back of the shock tower to replace the bellcrank, maybe all the way to pretty much sitting on the rear bumper/skid.

[Kol__ 3387]

All sounds very complicated bud, but excellent to see all this trial and error and we'll thought out development of the ideas. I'm sure you'll crack it!

7 hours ago, Frankster said:

Overall steering rods need to be parallel to the axel and the steering linkage needs to the at same point as A arm pivot

I get the bit about the steering rods needing to be parallel with the axle, as I've been trying to do the same on my DT-02 to reduce the bump steer. Not sure what you mean by the 'steering linkage needs to the at same point as A arm pivot' though mate?

[Frankster 2073]

5 minutes ago, Kol__ said:

All sounds very complicated bud, but excellent to see all this trial and error and we'll thought out development of the ideas. I'm sure you'll crack it!

I get the bit about the steering rods needing to be parallel with the axle, as I've been trying to do the same on my DT-02 to reduce the bump steer. Not sure what you mean by the 'steering linkage needs to the at same point as A arm pivot' though mate?

Sorry if I did not explain it correctly. The pivot point of the A arm is aligned with the pivot point of the steering rod.  See red lines in photo.  This helps eliminate bump steer from the factory 

[Frankster 2073]

Now with 4 wheel steering!

Mocked up the rear steering assembly.  Used blue tack to layout parts. 
ordere some 3M brass stand-offs and reused holes in FRP upper arm. 
 

I need to connect to a second servo to steering assembly.  Also switch out to longer dampers.

Feels good to overcome a huge hurdle. I wish I could 3D print like some of the other guys in this forum

Edited April 15, 2022 by Frankster
Fixed photo issue

[Ziddan 984]

That turned out real clean, congrats 

[Frankster 2073]

Thanks @Ziddan!   Almost there, not finished yet.  Looking at the example you sent to connect to a second servo. Luckily the Beetle body is big to hide the mounting of the second servo

[Frankster 2073]

Monster Beetle body mounted for mock up testing.   Rear steeling assembly is sticking out and needs to be cleaned up.  Will program the rear servo to be 50% of the front servo. 

Chassis tub too low for my liking and I will need to look at longer dampers or shorter damper towers to raise tub and increase ground clearance.

To do list includes final body, body mount, rear servo, electronics, raising chassis. 

[Ziddan 984]

1 hour ago, Frankster said:

Chassis tub too low for my liking and I will need to look at longer dampers or shorter damper towers to raise tub and increase ground clearance.

If you have some more m3 spacers and threaded rod you might extend the damper rods before attaching the eyelets that bolt to the lower arms.

Here is my tt02b with extended eyelets, more ride height:

Looks amazing with the body on

[Frankster 2073]

Thanks @Ziddan Great idea.   I need to check when I get home.  I am using cheap metal dampers and not sure if is using M3 threads.

 

I also found by changing to metal drive cups and dog bones I can get better ride height as well without binding

[TurnipJF 9872]

Instead of a second servo, could you perhaps mount a bellcrank on the rear shock tower, then run a pushrod from that forwards to allow both sets of steering to be operated from a single servo? You could adjust the rear steering rate by changing the pushrod position on the bellcrank.

[Ziddan 984]

40 minutes ago, Frankster said:

I also found by changing to metal drive cups and dog bones I can get better ride height as well without binding

In my pic im using the stock dampers and most likely you have some of those laying about, they seem alright IMO.

For sure smaller cups on both the diff side and hub side will allow for more droop, front arms were ok for me but for my the back ones i printed new arms that have more space for the cups so i could get some droop there.