Almost free CR-01 BTA and some lightweight side plates

[lowslowTJ]

OK so here is a breif write up of how to BTA a CR-01. Its actually relatively easy, and makes these things steer much better with improved Ackerman Angle for almost no $$$$ provided you did not cut the rear arms off the stock knuckels.

All you need are a couple of ~3mm spacers, one extra 3.0mm screw, some time and a Excto knife.

1)First you have to remove the lower coil buckets from the front axle and the long tie-rod from the front of the axle. Leave the short drag link running from the servo to the right knuckle in front. (If you are not running the stock coils then you can skip to step #3)


2)Trim the webbing off the bottom of both of the lower spring buckets like so:


3)You can now attach the long tie-rod to the rear arms on the stock steering knuckles (or if you are running some aluminum aftermarket arms if they have both front and rear arms) with the 3mm spacers under the pillow balls and the extra 3mm screw(if you are not running the stock coils and lower coil buckets then you are done).


4)You can now re-attach the lower coil buckets to the two holes behind where they were (moving the coil-bucket back a touch) and use the pillow ball for the push-rod to the shock on the back of the upper screw(see below):



5)You can also move the billow ball for the push rod to the lower hole if you flip the upper screw around so the nut is facing the tire. (I hope that makes sense).

-You may also need to move the upper coil bucket back on the frame rails so the spring does not buckle when it is compressed.

Let me know if any of this needs clarification:thinking:.

Also here are my lightweight (and polished) side plates. They were a PITA to cut and drill out of 3mm-1/8th aluminum plate, but they are about half the weight of the stock frame-rails and plastic side pieces. (These are not almost free, I just wanted to show off a bit )

[John74]

I like free to do ideas, i will try this out when i next have some time to rebuild my CR-01

[fatwoul]

Like the idea, and glad it works for you. I'm back working on my own CR-01 now, but it's all aluminium, including those super fancy axle housings from RC4WD, so my knuckles never had the rear arms. I guess I could dig out the old plastic ones...

Actually, I'm thinking I might even have enough plastic pieces to build a whole other CR-01, if I can get hold of the internals for the axles. If I can, I'm definitely trying this.

[lowslowTJ]

Originally Posted by fatwoul

Like the idea, and glad it works for you. I'm back working on my own CR-01 now, but it's all aluminium, including those super fancy axle housings from RC4WD, so my knuckles never had the rear arms. I guess I could dig out the old plastic ones...

Actually, I'm thinking I might even have enough plastic pieces to build a whole other CR-01, if I can get hold of the internals for the axles. If I can, I'm definitely trying this.

I have these on one of my CR-01s with this BTA set up, but yea it sounds like you can build a 2nd plastic CR-01! Cool!

http://www3.towerhobbies.com/cgi-bin...3&I=LXWKG3&P=K

[860Crawler]

Did you flip the servo as well so everything is BTA or is there not enough room?

[krapulax]

NIce scale lownslow, where did you get it and how much was it?

[lowslowTJ]

Originally Posted by 860Crawler

Did you flip the servo as well so everything is BTA or is there not enough room?

No the servo is in the stock location in front of the axle and pushes the right hand side knuckle from the front via the short tie rod which in turn turns the left knuckle via the long tie rod behind the axle. this fixes the Ackerman angle of the whole steering system. You can kind of see how it works in this picture but the front is a bit obscured:

Originally Posted by krapulax

NIce scale lownslow, where did you get it and how much was it?

The scale was a gift from my mom, and I have no idea where it came from. I will ask when I talk to her next!

[prusik333]

That's a great idea BTA steering, i think i will try that.......i almost trimmed that inside knuckle off too, glad i held off from doing that
great job

[lowslowTJ]

Thanks. it does improve the steering for sure!

[fatwoul]

Originally Posted by lowslowTJ

I have these on one of my CR-01s with this BTA set up, but yea it sounds like you can build a 2nd plastic CR-01! Cool!

http://www3.towerhobbies.com/cgi-bin...3&I=LXWKG3&P=K

Cheers, low. I might give those a go, although so far I've not had much success with Integy parts.

I'm definitely tempted to try and build a second chassis with the leftover bits. Could be an interesting build thread for here, in fact.

[AkFordfan]

Just got done with this, works great thanks for the tip.

[SteveVanB]

Just did the bTA mod. Nice free mod, and it works good.

[GraciousOne]

Cool idea for the Ackerman. However, how much difference does it make - i.e. turning radius was X feet, now it is Y feet with the "corrected" Ackerman.

The SCX10 has the same "backward" Ackerman setup, and it works pretty well. I am just wondering if the Ackerman is set up that way on these trucks (CR01, SCX10) just for convenience (i.e. steering link and tie rod on the front to keep it out of the way of the driveshaft), or if it is actually designed that way. Remember, Ackerman (well, zero Ackerman) is set up to allow the front wheels to turn with minimal (or no) scrub. This means the inner wheel is allowed to follow the tighter radius it should, and vice versa for the outer wheel. That's fine with an OPEN diff. But with a locked diff, the greater the difference in radius that the front wheels follow, the more scrubbing there is (more accurately, spinning) of the wheels as they are forced to rotate at the same speed by the locked diff. Reverse Ackerman, would, in theory, mean the inside and outside wheels follow a closer (obviously not identical) radius, thus reducing scrubbing caused by the locked diff. This could, in theory, improve steering, not that anything with a locked front diff will turn on a dime. Again, if it were an open diff, going with "correct" Ackerman is a no-brainer. Just wondering if, with a locked diff, reverse Ackerman might actually make a bit of sense.

That's why I'm so curious to know if in reality, correcting the Ackerman will result in a tighter turning radius. Thoughts?

[OSRC]

It did not make any improvements on mine - in fact, with the ackerman corrected, mine turned worse. Outside wheel does not turn quite as far and couldn't dig in. Cannot quantify it, but definitely felt it out on the trail. Went back to the links in front of the axle. If I had open diffs, I imagine I would have had much better initial turn-in and handing would be better in general, but with locked diffs all around, not so much. That's my experience anyway.

Having the link behind the axle puts it out of harms way as well. 1 less thing to catch on the rocks. Nice benefit in and of itself.

I would imagine it is set up that way for convenience.

[GraciousOne]

Thanks for the response, OSRC - I appreciate it.

[Scottd9990]

Seems to me that having the steering rod behind the axle, it's pushing the wheel to turn right, vs Pulling when the rod is in front of the axle. I would think there would be some flex there. Not sure I am understanding this correctly?

Thanks!

[860Crawler]

Originally Posted by Scottd9990

Seems to me that having the steering rod behind the axle, it's pushing the wheel to turn right, vs Pulling when the rod is in front of the axle. I would think there would be some flex there. Not sure I am understanding this correctly?

Thanks!

I guess this only matters if you plan on only turning right from here on out

But really, the rod is pretty stout, I've only bent a steering rod by hitting a rock