Mid-motor B1, B4, B6

[radioactivity]

Thank you guys!!!

I bought an empty B6.1 laydown empty case. I had a goldpan that I took apart and started taking lots of measurements by eye and digital calipers. Everything looked promising.
I made a template to help mount the case to the goldpan.
When the black chassis went on sale for $20 I bought a couple and earmarked one for the build.
I started hunting for B6.1 trans and found a laydown and a layback on Ebay for an awesome deal.

I have used the B4/B44 carrier/bone arrangement before and the B6.1 trans gave a little more leeway for bone travel/engagement.
The ball stud mount on the trans was almost perfect, I did swap the rear hubs side to side to get a little better camber turnbuckle alignment.
The height of the tall tower mounted on the trans is almost exactly the same as my world’s.

I’ve used B6 rear shocks before and they are very close in length to the 1.18” sale shocks.
I did play with the rear shock length a little, settling with the longer B6 lower eyelet both front and rear.

That said I was hopeful and the results were better than expected.
A predictable happy accident!

I still need to change the front springs, they are way too stiff for dirt.
I have started a project to get a little more weight on her tail, hope this one works out.

Chuck

[RCveteran]

Wow, excellent build, now I need to resist taking apart my B6.1

[radioactivity]

Been awhile...

I spent a little time putting together a Build of the Month car. Hope we get some more participation, it's so cool to see these builds.

Using the laydown trans may have moved the F/R bias a little to far foward.
In an effort to shift the F/R bias back a little I made a plaster mold from the epoxy part show above. The original epoxy part came in at about 3/4 of an ounce.
I then embedded lead shot into epoxy and made a second part in the plaster mold. That part came in at about 2 oz.
The parts I made both act as ballast and as a spacer that fits where the B6.1 rear "D" arm mount would fit.
The car with a shorty pack, body, motor, etc. being compensated for is still about 3oz under the 1499g minimum due to the lipo battery weight.
Guess I won't be looking for ultra light body, motor, Esc, servo and receiver

Chuck

[XLR8]

That's a clever way to add ballast, Chuck.
3 oz is a lot of weight to add but that's a good problem to have - i.e. build the car as light as possible so you can position any necessary added weight where it's most beneficial.
Certainly, it's best to keep the weight on the chassis and as low as possible. Some of the more basic sensorless brushless ESCs tend to be heavy. In my more recent runner builds, I've been resisting the temptation to go the lazy route and simply mount the ESC to the rear shock tower (as I've done in the past) but make room to stick it to the chassis plate instead.
It would be interesting to know to what extent the B6 parts you're using on this build affects overall weight.

[radioactivity]

The weight savings by going to the B6.1 transmission was not as much as I expected.
I took some estimates early on. A little less than a 1 oz. in total.
That included 6 gear with spur and ball diff, bulkhead, motor mount, trans to bulkhead brace , wing tubes and tower.
B6.1 included trans with spur and slipper, waterfall, tower, B6.1 wing mounts, molded epoxy tower spacer and ballstud mount.
I did not include the leaded or leadfree spacer mentioned above because it could be substituted with a very small plastic spacer that would weight virtually nothing.
I lost a little bit more when trimming the chassis sides and to clearance for the spur.
I did weigh everything with an older letter scale, I really need to get a small digital scale to be totally accurate.

BTW the leaded spacer vs no spacer moved the F/R bias toward the rear about 1/4". Again less tha I expected.

Chuck

[radioactivity]

Just a short update
I got a cheap Spektrum receiver that needed repair on Ebay. Fixed it, fired her up and it works fine.
Dug a little deeper in the pocket and popped for a Savox Black 1251mg. Really a nice servo.
Servo arm was free.
Looking at ESC motor combos, probably Associated... Black Friday/Cyber Monday is coming up!

Chuck

[KidAgain]

she looks good.....................................

[Nick]

This is fantastic, I really miss how much of the hobby has gone away. Great project!

[radioactivity]

Thanks guys

I did get a Reedy motor/ESC during Black friday. Saved a little on the two.
Fitting both in the chassis was fairly tight.
I moved the servo forward and to the right to gain a little more clearance.
The sensor wire that came with motor is too long so I have a 150mm on its way.
Got some soldering done and preliminary binding, endpoints etc done.
When the shorter sensor wire comes I'll more permanently mount esc and receiver.
Not really sure where to set timing, seems like 40 on the can marks is close???

Chuck

[XLR8]

Looks great Chuck. Neat and tidy.
One of the very best mid conversions I have ever seen.

[Headling]

Nicely done! looks factory

[Lavigna]

Fantastic build so far. Great innovation.

[radioactivity]

Thanks so much guys!

I appreciate positive feedback.
Still have a few mods to do before I call it "complete" , if that is possible.
The body/paint is still undecided but getting narrowed down.

Chuck

[radioactivity]

So after a quick bench test to check esc, steering and motor functions it was obvious that the rear wheel/tires were way out of balance.
I did not have a wheel balancer nor did I want to spend $30 to order one and wait. More fun to build one anyways.
I did find some black plastic spacers from a TV mount in the garage. I'm a terrible hoarder of small bits and obscure pieces.
I had some old bearings that I cleaned and a short piece of 3/16" aluminum tube. I mashed the tube very slightly to get the bearings snug on the tube.
Most of my wheels are 3/16" axel so this will work for those.
The hand-held balancer worked perfect taking out all the rear wheel/tire vibration.

Chuck

[XLR8]

That's a great tip Chuck, thanks for posting it.
By the way, I've noticed that wheel/tire sets from Kyosho usually run very true and don't require balancing.
For my other vehicles, I've used short pieces of lead solder as wheel weights -- some of the short course wheels require a lot a weight to bring them into balance. Anyway, I'll usually attach the weights with electrical tape but they eventually fall off. I feel like there must be a better procedure. Any advice here?