King Blackfoot Custom Chassis Mods and Improvements

[ARocketScientist 17]

Hi,
this is my first post here. I just figured I'd share this with the world, since I haven't seen any of those mods anywhere else. 

If you're only interested in seeing what and how, feel free to skip the next lines and check out the links below (hope that's allowed?).

A quick rundown on this trucks history. I got it as a birthday present when I was 14. It was a dream come true and was quickly tossed in the corner for the next 13 years or so to come. I finally dug it out several years ago to strip it of its body which I ran on a Savage 25 a couple of times. Not a good idea, so I put it back where I found it.  
Over the years I did spend at least some time with the Blackfoot, however, and every time I ended up somewhat disappointed with the driving experience. The suspension was too stiff, unwilling and generally awkward. The worst part to me has always been the steering and it always spoiled the fun with its wobbly behaviour and useless layout (no offence).
Anyways... I recently found myself having a brushless Racestar motor/ESC combo and 9kg digital servo lying around - both new since I only ever ran them a couple of times on another RC. On top of that I also had 4 Savage X shocks left. Yesss, you read that right! So I decided to put all of it to good use and revive my very first RC car after its 18 year slumber. That said, I just couldn't leave the steering the way it was - I mean the inner tie rod ball-joint positions are just ridiculous! What were you thinking, Tamiya? (Haha still no offence).

Now, long story short. I decided to rework the poor front suspension geometry and throw in all the goodies I mentioned above into the mix for good measure. This here is the result so far. I've got more mods lined up - but I'm not telling. The facia is missing because this way the truck looks freakin evil!

You can check out some pictures of the mods under this link:
https://goo.gl/photos/F2X7zgJy7UHNmhmC6

Here's a (very) short video of the steering setup:
https://www.youtube.com/watch?v=B2PTnfTFsFQ

Here's the first ever trial run - you are witnessing something here!
https://www.youtube.com/watch?v=leMEaFB_w5M

I'm not going to bore everyone and their dog by listing everything I did and parts and electronics I used. Just ask if you want to know or see anything specific.
 

[ARocketScientist 17]

Alright folks, I renamed the title because what started as a small side-project to put some spare parts to good use has set me on fire now. I rediscovered my love for the truck, if you will, and decided to go deeper into improving it. Gotta rush to work now but will upload pics and videos of the progress later in the day. 

[ARocketScientist 17]

Henry Ford supposedly once said "Vision without execution is just hallucination".

This truck always seemed... unfinished to me, like it was asking for more, like it was abandoned half way through it's development. Now that I'm all grown up (ha! I'm not) and an automotive engineer who spent the last 5 or so years in chassis development at Ford, it's just feels right to finally try and mod it up to it's full potential. I've got to admit that this project sort of grew out of proportion and got me totally excited. What began as a plane utilization of spare parts reminded me what got me hooked onto this hobby in the first place. I've got so many ideas that I don't even know where to beginn. That said, you must know that this build isn't just about improving stuff. Some of the mods will be done just because I feel like it

Alright, enough talk. Here's the current state of the truck. Let me give you a quick rundown of what's been done so far. 

So first on to the electronic components. They're still a bit messy in terms of wiring, but I'll get to that later. The combo as it is, is super fast and powerful and has the truck pulling wheelies with the slightest touch of the throttle. 

• Racestar 3900 KV sensorless BL motor
• Racestar 60A ESC
• JX 9kg digital metal gear servo
• 2.4 GHz Turnigy TrackStar TS4G TX and RX with integrated gyro

Here is the beast itself. First I've fitted Savage X big bore dampers onto it. In the rear it was more or less plug and play. In the front it took a fair bit of customization. There are certainly different options to do it but I went with a center mount, which, as a plus, provides the truck with a mean look. I'm contemplating if I should make a custom shock mount out of a 4mm carbon plate I have lying around. What do you think? 

Here's another pic of the mount. As you see I used two spare parts that came with the truck and of which I'm not really sure anymore what their original purpose was... 

And another one from the back along with the frame that replaced the original servo cover. I always felt like the cover had somewhat of a tractor look to it, which I dislike. It's arguable if the new "frame" itself has any advantage over the said cover but I like it that way. I'm not happy with the lower attachment points of the front shocks, however. More on that later. 

That way front and rear towers are connected and provide each other stability (at least that's what I hope). The side rails are mounted onto the frame itself. I used the V-shape of the mounting points, which btw never had any real purpose on the KB, as guides and it turned out pretty nice, I think. Just for the record: the tubes are 6x4 mm aluminium. They play along nicely with M4 stainless steel screws that also act as thread cutters. I'm not adding a brace connecting the two side rails, in order to allow for deformation in case of a crash. Those rails are easily replaced.

Here's another look from the side. Looks like this truck means business. 

I was or still am thinking about making my own servo mount but for now find it charming to have the servo installed with the original parts - even though it's sitting there upside down now. 

Then I used the same tube to stiffen up the frame. The two that are close to each other replaced the plastic part that used to sit there for the same purpose. The one further to the front I added myself. 

Which smoothly leads us to where it all began - the steering. You might have seen my proof of concept from the original post. So after that I went a step further and also replaced the bulky links which were bothering me because of their clunky-chunky appearance. 

For now I'm still pondering on the geometry of the steering setup and might change a thing or two in the process. I might still add a brace or two connecting the two steering arms, just to be on the safe side in terms of durability. Later. The arms are from an XRay T3, in case you were wondering, and are each sitting on a pair of steel-ceramic-hybrid ball bearings. Those I mistakenly bought at some point. One had to be modified, as it was lacking a side arm which was necessary for this particular arrangement. I made it out of a piece of 1mm carbon, which is stronger than one might expect from such a thin material. Carbon is great, folks.

In order to prevent the steering from ripping the chassis apart I put threaded sleeves through the frame and secured the whole thing with M4 screws from top and bottom. 

I know, it's not the most elegant looking solution but at that point in time I didn't know how the project would spin out of control on me. The ball pivots are connected by an M3 threaded rod I cut to right length. Here's another view through the frame.

The biggest issues that this setup brings along is that the steering is now the lowest point of the vehicle. I'll probably have that fixed in my next post in that I will make a shield of some sort underneath the truck. Think skid plate. 

 

That's not all I've done but this should suffice for a first comprehensive overview. Coming up next are broken C-hubs and how to fix them, reduction of suspension free play and robustness improvements, air-lock wheels and maybe more. 

Thanks for reading and good night. 

[Saito2 2816]

Welcome! Very nice modifications. I really need to track down a King Blackfoot for my collection. I love the design evolution of any chassis. A brief run down of its history: The KBF is the last in a very long line of vehicles to use the ORV (off road vehicle) platform. It originally came out (as the Subaru Brat) as a replacement chassis for the SRB (special racing buggy) which was Tamiya's first buggy chassis (1979). It eventually underpinned the Frog (and Lancia Rally) before being modified majorly the first time into the original Blackfoot. It gained, among other things, a new tall front shock tower, bigger steering blocks and uprights and a cover (that you mentioned) to protect the electronics (while covering the exposed chassis under the high-riding Ford F150 body).

Extremely popular, the Blackfoot sold in record numbers despite being flawed in several areas. The Super Blackfoot was the first round of revisions which focused on the woefully weak rear gearbox. The SBF also lost the rear trailing arm suspension and gained a wider version of the original BF's front suspension. The King Blackfoot finished the transformation by revising the front suspension totally to a more up-to-date standardized design. By this point, the chassis itself was the main remnant from the old ORV days. The pieces you used as front shock mounts are the original ORV battery end caps/ side retainers. Nice re-use of them! 

Sadly, your right that the chassis could have used further development in certain areas. Rather then give the old girl another go around, Tamiya choose to move on to another platform (Wild Dagger/WT01,WR01). So the King Blackfoot wound up being the last of the line.

[Frog Jumper 946]

I like your steering mod!  Do you ever scrape it on the ground/pavement???

Terry

 

[ARocketScientist 17]

@Saito2

Hey thanks much for the interesting insights! From what you wrote it seems to me that Tamiya simply decided to abandon the outdated ORV in favor of more advanced and streamlined designs. The fastener complexity alone is crazy on the ORV and many parts seem more complicated than they could've been. But hey, I'm not complaining because that's part of what makes modifying the truck so much fun. Besides, it's easy to criticise outdated technology in general. One should never forget, though, that in order to understand the present and shape the future, one should know the past. I enjoy figuring out the background of how things were done and I always learn a thing or two in the process. So thanks again for sharing your knowledge.

@Frog Jumper

Not as yet, not during the very few trial runs I've had stop far. But then again I do share the same concern. That's why I'm intending to make a skid shield to protect the steering. I've got a draft on my mind already and will share it when it's ready.

Hopefully I'll be able to find some time today to post a few things. Stay tuned

 

[Frog Jumper 946]

Where did you get blue wheels???  Or are those painted???

Terry

 

[Saito2 2816]

What's funny is the King Blackfoot, in many ways, is even more streamlined and simplified design-wise than the original Blackfoot. Early Tamiya designs (as well as other manufactures at the time) could be wickedly over engineered. But its this feature that makes them interesting to tinker with and drive. To this day, Tamiya still can over-think things (i.e. CR01 platform) but its one of their charms. Once the proper design architecture was nailed down, alot of vehicles began to look and act the same. Better performing, stronger and lower-parts count doesn't always add up to perfection in my eyes unless one is being totally pragmatic about it.

[ARocketScientist 17]

@Frog Jumper
I painted them blue. Must've been some 15 years ago. The paint is impressively persistent! 

@Saito2

"To this day, Tamiya still can over-think things (i.e. CR01 platform) but its one of their charms. Once the proper design architecture was nailed down, alot of vehicles began to look and act the same. Better performing, stronger and lower-parts count doesn't always add up to perfection in my eyes unless one is being totally pragmatic about it."

Your wording is exactly how I feel about it. I'd sign that! 

 

Btw, I've uploaded a little something to YouTube. It's a short video of a test run that I did the other day... Just to see if the steering is working properly. It's still the initial setup, though. 

 

You guys have any idea why I can't upload a profile pic? It's definitely less than the permitted 1024kB but I get an error saying it exceeds the size limit. Weird... forget about it, I figured it out

[Saito2 2816]

Thank you for the kind words. That King Blackfoot of yours is a bullet! Wheelies on demand. Nice.

[ARocketScientist 17]

Alright, so broken hubs... After the run you see in the video above I noticed that one of the hubs was broken. At first I was thinking of looking for a new one or even completely interchanging the whole front suspension for something like this:

But I decided not to and instead repair the broken part and improve its robustness in the process - which only time will tell if I managed to do. I'll show you guys what I did on the broken hub but it was the same procedure on the other side. To give you an idea of what I'll be talking about, here's the broken part.

Anyways, I decided to make bushings of some sort for the attachment holes to the lower control arm. In fact, the pic above was taken after I already popped one in. Pop rivets seemed a cheap and good solution. With their 4mm outer diameter they also have the benefit of better distributing the load introduced into the hub during impacts, hence (hopefully) improving the robustness. I drilled out the hub to 3.8mm to receive a snug fit of the rivet.

Ready for the next step

Recreating the missing piece with Bondiq. Bondiq is a sort of resin, that is applied in form of a fluid and hardens under UV light. I'll be honest with you, I doubt it will stay there for long but at least it looks cool.

In direct sunlight it almost instantly hardened, so that I was able to file it in shape. Esthetics, you know.

Next step - glue it up! There's nothing wrong with some glue if you want to combine things that are ought to stay together and never be taken apart. 

The rivets widened the hubs, so in order to make them fit the LCA (= lower control arm) I had to cut away a bit of the inner attachments. No big deal.

The result:

I guess that's enough for one post with all the pics and stuff... If I keep posting more I'm afraid one will loose track of where one mod ends and the next one begins. Please bear with me on that one... 

[Frog Jumper 946]

Those KBF/SBF/BD knuckles are hard to find.  I replaced the ones on my Bush Devil with those from a standard BF.  Works great, and allows me to fit a vintage set of Parma steering thingies that help to reduce bump-steer.  Maybe you can fit the standard BF knuckles on the KBF A-Arms???

Terry

 

[ARocketScientist 17]

I guess I'll just stick to those for now. If they break I will probably get back to the idea of going for entirely new parts. And if they don't even better

 

It's time to talk about free play in the front suspension. Apart from the steering and shocks which are luckily already covered, the stock suspension components are naturally showing some free play considering the age of the truck. I mean I did toss it aside at some point but before that and every now and then, it had to endure a good amount of bashing. The LCA-to-chassis free play wasn't even that bad all things considered and was easily fixed by shimming the arms. As opposed to that, the turnbuckles were causing a significant amount of vertical wobble to the front wheels, so shimming didn't help much.

I was lucky enough, however, to find some brass tubing with the inner diameter to perfectly fit the shaft-screw of the turnbuckle. After pulling out the shaft, the turnbuckle had to be drilled out a bit for the tube to snugly fit in. 

I then cut the tubing to the right length... 

...and put the pieces into place using a pair of pliers. I made one piece stick out of the buckle one side by about 0.5 mm...

...and filed it down to the thickness of the shim I still had to apply here. 

I'm actually pretty happy with how it turned out because there's virtually zero free play left in it! I'll post a quick video showing the difference between before and after. 

Let's see how durable it is.

[ARocketScientist 17]

As promised, here's a quick comparison of stock shimmed vs modified turnbuckle. The improvement is apparent. Here's the link to the video:

 

Today I also ordered a pair of 12mm hex adapters for the front axle (part number: GPM DT3010F-R):

http://www.ebay.de/itm/351853724417?_trksid=p2057872.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT

I'm planning to grab this set of wheels, as soon as they're back in stock. Approx. 10mm bigger diameter and around 8mm wider. The reviews on those are pretty great. Check out the wheels here and tell me what you think:

http://www.banggood.com/4PCS-Wheel-Rim-Tires-HSP-110-Monster-Truck-RC-Car-12mm-Hub-88005-p-1072827.html?utm_campaign=android-share&utm_source=google-play&utm_medium=organic&android_share=1&_branch_match_id=373961846384457014

[ARocketScientist 17]

Ok folks, so I went for a test drive the other day and everything was looking fantastic... until the RX failed that is and instead of stopping the truck kept on going... and going... and... 

Yepp, a lot of things broke, including the knuckle that I "improved" lol So much for durability improvement. Screw that... back to the drawing board. I'll have to come up with something better. That said, I wasn't satisfied with the performance of the front suspension anyways. The steering worked better than ever (of course :P) but the damper attachments still sucked. But more than anything the front lower control arms just aren't doing their job properly. Ok so the truck is asking for a new one and I will deliver. 

In the meantime I distracted myself with a new mod. I think I came up with it, which means that I have no idea if somebody has done it before - but I bet they did. Anyways, it's taillights. These here are for my XRay, but I've got enough of this stuff to outfit the King with that as well.

Please disregard the paint smudges...

 

Oh and I think I finally found the right body for the truck, too. It'll be this one, although in a different color. The pricing is pretty neat, too. It's just 28€ including shipping. I'm hoping that I can carry over some stuff from the original body like, say, the bumpers, and that way merge the present with the past. 

Source: http://www.modellbau-etter.de/rc-car-zubehoer/karosserien/index.html

[Frog Jumper 946]

My thoughts...

Replace the uprights and knuckles with standard BF uprights and Parma (or AmPro) knuckles, while moving you steering mod to the top of the chassis...

1. Standard BF uprights and knuckles are common and cheap.  Parma knuckles are very rare but eliminate bump steer (I have these).  AmPro makes a modern version of the Parma knuckle that should work just as well (from the video I watched, not from personal experience).  
2. Moving your Steering Mod to the top of the chassis eliminates issues with any of you steering rig being stuck by debris, etc.  

One too many beers???  Probably...

Terry

 

[ARocketScientist 17]

@Frog Jumper

I'll consider that but I'm actually thinking of making my own. I'll explain why later on.

And remember, alcohol is no answer! It's a question and the answer is yes! 

[ARocketScientist 17]

Aight, so after giving it another thought, instead of going thru the pain of making my own hubs I'm going to divert from the common design and try a straight knuckle to control arms kind of thing.

I was going to go ahead and make me new front control arms, as I feel that on the front those little T-Rex arms the truck comes with aren't working properly anyway. The only thing I'm worried about at this stage is if I can get the upper arm sit tight enough in the mounts as not to flex back and forth, as this would basically ruin the whole idea.

So fingers crossed! I'm off to the drawing board...

[ARocketScientist 17]

Dear diary,

after careful consideration and calculation of value for time and money, I decided to ditch the idea of making my own suspension components in favour of buying CNC machined parts from a HSP 1/10 monster truck. I placed the order and am currently eagerly looking forward to the parts arriving at my door step. Just for the record, here's what I ordered:

Aaaaaand in the meantime my monster wheels finally arrived from China! Man, these things are a blast and the best value for money I could find. In fact, they'd be worth double the price! They come un-glued with propper foam inserts and already pre-assembled. The rubber is soft and nice to the touch, the rims seem sturdy and weight wise light enough for the truck to handle. Unfortunately I cannot take those bad boys for a spin right now due to broken front suspension...

I don't need to tell ya'll what's before and what's after... 

And just for fun I placed the wheels next to my beloved Savage X. Cute

 

Stay tuned... I guess... 

 

[4ferraras 18]

Did you get those new CNC parts? Did they fit? I've been looking for an upgrade for my SBF and KBF.

[ARocketScientist 17]

Not as yet. It might take a while for the parts to drop at my doorstep. I'll keep you posted. 

[ARocketScientist 17]

The wait is over! The first batch of parts finally arrived, it's looking good and I'm excited to show this to you! Looks like I've made the right choices of parts. I'm too tired to say much more or to put it all together. There's gonna have to be a lot of shimming, adjusting and modifying to be done to get those puppies fit but it'll be worth it. King Blackfoot 2.0 coming up soon!

So here's a size side to side with the original parts

Especially in the front there's gonna be a huge geometry change. 

The front and rear control arms are slightly different but you could replace the rear ones with a set for the front and have a variable rear toe. But... nah... Here's stack of those arms. 

Rear knuckle...

Front knuckle and hub assembly...

Interesting ist the size of the inner and outer bearings

The control arms are quite narrow and I'll have to cut some material off of the original mounts to make the control arms fit.

That's it for today... 

 

 

[ARocketScientist 17]

Today I gave it a start.

First off I had to cut 4mm and 8mm off of the front and rear lower control arm mounts respectively. What I admittedly did not consider, or should I say didn't expect, is that I actually broke into the rear gearbox in the process. On the front a small hole also appeared when I took away enough material. My concern is that cracks might be the consequence, eventually leading to the gearbox and/or front tower mounts ripping apart. So I'm thinking if I maybe should reinforce those weak points. But for now I'm concentrating on making everything fit properly and have the suspension in place before carrying on to re-building and reinforcing the steering. There's a lot of customizing and shimming and such to be done, I need to come up with a nice rear shock attachment and make a few other adjustments before I'll be able to take this bad boy for a spin. 

Check out how the wheel base grew by a few mm and, what's more interesting, the front track width also increased! I'm going to use hexes with 7mm and 4mm offset on the rear and front axles respectively. We'll see how it goes... 

On the rear things more or less stayed the same geometry wise, except for the slightly increased toe in. And last but not at all least, I'll need to order another set of CVDs because I miscalculated the required length. I used the shaft-part of each of the CVDs to mount the wheels. 

Consider this a proof of concept. I've only mounted the parts loosely on one side of the chassis, which makes for nice comparison shots. I'll be back with more, when there's more. Btw, let me know if you want the part numbers.

 

[ARocketScientist 17]

Getting there...

[ARocketScientist 17]

Update update update...

So I finally got everything together and also found the time to assemble it all into one piece. Bzw, in the process I moved the steering up on top of the frame and away from those pesky obstacles on the ground... There's still some work to be done like balancing the wheels, figuring out proper suspension settings, tidying up the electronics, new bumper, wheely bar and applying some Loctite for good measure here and there - to name a few. And of course there's the body but that's another chapter. For now, I'm pretty impressed with how well the project actually turned out! 

Watch for yourself in the fresh "mayden drive" video below. At the end I lost the steering but it was easily fixed and nothing was broken, just a slipped bushing, that's all. 

 

 

I'll be back with some pics and explanations. If somebody is interested, that is... I'll definitely do a video overview of what has been done and modified but that could still take a while.