MAC FAB buggy build, V3

[MAC FAB]

I'm guessing this is the place for the build, being a non-crawler. 1/4" DOM tube and most of the required mtal to build it up. The parts gathering so far....
It should be about 1/7 scale, like a UDR, on Bomber RTR KR2s. More like a class 10 pre-runner than a class 1 version.

20190512_130413 by MAC FAB, on Flickr


20190508_080502 by MAC FAB, on Flickr


Looking something like this:


20190503_131843 by MAC FAB, on Flickr


The upright with the arm tabs will be under the A pillar, not as seen here. Cab needs to be stretched a bit as well. Vision rendering #1.

[jonnywachter]

sweet!

[MAC FAB]

Originally Posted by jonnywachter

sweet!

I'm glad you have the steering on your program figured out, I may "borrow" some of the concept. Trying to shoehorn some bell cranks between the front pivots in their proper orientation may be a challenge, so horizontal with a servo above them may work for plan B. Chassis lines are pretty much worked out, that upright with the tabs will keep its location, connecting to the new B pillar location. Going for the 4 seat dual sport look. I need to look at UDR shocks to see about getting 2 per wheel, although the singles will work in a pinch. I will get one side of the front done so I can try to figure caster into the geometry and hopefully no or very little bump steer when done. Once the front is figured, it should build up quickly.

[jonnywachter]

The steering works right now but I've been really considering doubling back on it and trying to make a rack of some sort. TBH I've put so much time into the design that I'm pretty burnt out on it. I'm just having fun driving it right now!

[MAC FAB]

I so hear that, my Bomber was the same thing. It has a couple fine tune things still to be done with the front arms and shock tuning, but meh, I'll get to it later, going driving instead. That said, it is quite satisfying when you make something totally outside the box and it works. Hopefully this unequal length A arm front end does the same. AE SC10 bell cranks are 1" wide, Slash are 1-1/2", so I may have tweaking options, they are just ugly in front of the arms for the whole world to see. Guess I could always make metal ones.....

[MAC FAB]

Arms are about done. By going for broke (literally), it will cycle 4-1/4" up front, from binding droop to binding bump, with an overall change in track width of 1-1/8", sitting 13-1/2" od at ride height. So in theory, cycling +/- 3-3/4" should work all day long. Bump steer should also be minimal, but I havent mocked that yet. I hope to be having some tangible progress this weekend.

[JatoTheRipper]

Heck of a start! Looks good.

[MAC FAB]

3 hrs into it and all I have is this. The chassis is stretched about 1-1/4" to become a 4 seater. It dwarfs the Bomber chassis I have waiting to become something. Plan "A" A-arms need to mount about 1" inside the side rails to work so the track width stays at 13=1/2" like the UDR, which doesn't thrill me. Big plated mounts may save the day there. The chassis can easily become a regular A-arm front end and nobody knows the difference. The body will hide all that nonsense anyhow, so why should I care, right?

20190525_151758 by MAC FAB, on Flickr

[MAC FAB]

Tons of chassis progress today. I think it will need to be traditional front A arms, because its getting heavy quickly. That along with some UDR KR2 takeoffs for a stiffer tire. Pics to come, no time to upload them now.

[MAC FAB]

20190601_172305 by MAC FAB, on Flickr

20190601_172104 by MAC FAB, on Flickr

20190601_171848 by MAC FAB, on Flickr

20190601_171824 by MAC FAB, on Flickr

Progress. Motor and trans need to be decided on as well as the front suspension format. In hindsight, I probably should have put a little more roll into the roof line. Its getting a "B" and "C" pillar added, an "X" in the roof, a bunch of other triangulated bars..... just like the 1:1 chassis builders do.

[looneybin]

Nice start!

[MAC FAB]

Thanks. This one is the fourth metal caged build, and man, how much easier it is being larger scale than the standard Baja Rey/SCORE TT scaled rig. There actually is room to work. If time were only so easy to come by to build it. I want to try boxed arms up front like the rear gets, but some 10 or 12 ga arms would be less time consuming. I need to throw all the parts on a scale and weigh them, being I really want to use a Slash tranny for the extra cabin space it would allow for. I suppose with moderate power on 3s it would survive keeping the diff.

[MAC FAB]

Prototyping some 18 ga.rear arms, shooting for 4-1/2" to 5" of usuable travel. Building some 10 ga. front arms tonight, hoping to cycle close to the rear numbers. This sucker is a BIG car. Looking into a FLM Slash Super Tranny for it to keep the weight bias towards the rear and to take all the abuse I can throw at it.

20190606_101500 by MAC FAB, on Flickr

[MAC FAB]

Pictures are worth 1000 words.

20190606_200930 by MAC FAB, on Flickr



20190606_201211 by MAC FAB, on Flickr


20190606_201925 by MAC FAB, on Flickr


20190606_201433 by MAC FAB, on Flickr

[MAC FAB]

20190620_181350 by MAC FAB, on Flickr

20190620_181418 by MAC FAB, on Flickr

20190620_181333 by MAC FAB, on Flickr

Mock up bulkhead. For now it will stay as a camber link, a wishbone upper arm may get into the mix, or a J arm. Slowly moving along.

[Gula]

Impressive fab skills! What is your occupation 1:1

[MAC FAB]

Originally Posted by Gula

Impressive fab skills! What is your occupation 1:1

Thank you for the kind words, and a 1:1 construction worker for the daytime gig. I've had a lot of exposure to off road cars, buggies in particular, so there lies the passion for building them.

[MAC FAB]

Making progress and am coming to the crossroad that I am relatively clueless about, that being electronics. Gonna try putting the horse in front of the cart by mounting the electronics before boxing myself out with chassis members. I'm guessing Big Bertha will tip the scales ~20 lbs. I would like to runs 3s lipos, and have no need of going any faster than 30 mph. I am looking to go the cheap route to get it running (it this things sucks, I don't want a fortune tied up in it, cool static model for plan B), so can anyone suggest something that foots the bill? Motor, esc and steering servo. Its theoretical purpose is for shooting video, in car in particular. Thanks in advance for any help.

[MAC FAB]

20190803_184815 by MAC FAB, on Flickr

20190803_184843 by MAC FAB, on Flickr

20190803_184640 by MAC FAB, on Flickr

[MAC FAB]

In keeping with the 2 steps forward, 5 steps back progress theme on this build, its time to scratch the front shock format pictured above for what is looking to be single, Yeti rears, are back into the equation. I can't effectively tune the shocks with the spring rate required as seen above, and body lines for the hood will suck with the LA Rams shock mounts when all tied in to the chassis. Leverage ratio is waaaaaaaay out of whack, nearly 5:1. Longer shocks with buckets on the bottom of the arms appears to be the solution.