Baja 5B Electric roller for $345 should I do it?

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Welp back to cheap aluminum chassis, the impact with the curb twisted the steel plate in the front of the Kraken RC polymer chassis. TBF it probably would have done the same to an aluminum chassis but I'm disappointed they didn't use spring steel for the internal plate. Totally my fault but at least the aluminum chassis are cheap to replace.
 
Taylor rc working on this for Baja

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I'm not buying expensive chassis anymore unless they make the angle part out of spring steel. If you hit it right it WILL bend even if it's made from 7075 that's just the reality of 28lbs of weight concentrated on 4mm of aluminum in the right direction. The only way to get around that is to make it from something that would flex and then return to it's original shape.

To be clear it's not that it always bends, it's just that once in a while you hit it just the right way and it does.
 
Wish I'd known about this earlier: https://www.ebay.com/itm/126498428700

Requires you to drill two 5mm holes in the bottom of the chassis to fix the plate on the wide end. I image the best way would be to fix the plate to the chassis with the existing screw holes and then use the plate itself as a template. I have a tabletop drill press so this is trivial. You could also drill those holes out larger and fix press in nuts if them if you wanted to get fancy,
 
Cheaper option for upgrading your Baja shocks: https://www.ebay.com/itm/177594405702 (there are also ones with silver ends available)

I'm pretty sure these fit the standard 16mm shock bodies. They have 8mm shafts and aluminum shock pistons with O-rings.
 
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With the 10mm shaft big bore shocks the shaft displaces so much oil that bleeding them in the usual way causes problems. The shafts will "suck" back into the shock at full extension. To solve this I push the shaft in *most* of the way stopping at 10mm of shaft sticking out (not including the shaft end). Then I pull halfway out before replacing the bleeder screw. This prevents both rebound and retraction and also causes a cushion effect just as the shock is fully compressed that keeps the piston from slamming into the cap. Maybe this isn't "correct" but the shock works better than if you do it the "right" way.
 
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So as it turns out the chassis could be fixed the plate wasn't twisted the plastic body of the chassis had developed a slight twist in it from being subjected to the radial shock load at the front end (an aluminum chassis likely would have been worse). Warmed it up in the oven at 180 degrees clamped at the front end in a bench vice and and twisted it the opposite way till it was back in shape and fixed. Also the front plastic bulkhead had developed a deformation with the hinge pin holder on one side pushed up higher than the other side. I boiled that for 20 minutes and pushed it back into shape. The hinge pin one one side was also bent and needed to be replaced.
 
So the X-Maxx springs fit the rear shocks perfectly. I also switched to 1200cst shock oil front and back and with the increased damping and harder rear springs it just glides over rough ground now.
 
If you need the plastic holders, or the cross pins for a Baja diff those partts are almost impossible to find on their own. The plastic gear holders come either with a new deferential or as part of a $25 parts tree.

However, the Primal RC Raminator differential internals are basically identical to a Baja 5B diff/

https://fearlessrc.com/product/prrmt108/

https://fearlessrc.com/product/prrmt106/

The perforated limited slip disks will fit an HPI differential but NOT a Rovan diff because Rovan uses a 0.5mm thick disk and HPI uses a 1mm thick one. Though you could always lap it down to 0.5mm.

Also, a Primal RC Challenger diff will fit a Baha 5B, though it uses HD size drive cups and you can't swap them with HPI uses because they use a flatted shaft and screw instead of a pin. For the price ($65) it's a nice upgrade.

https://fearlessrc.com/product/prcr0091/

https://fearlessrc.com/product/prcr0123/

You could probably use Rovan V2 drive cups and gears in it (they use a similar D shaft design). The issue with using standard cups is there are no holes in the diff to allow the pins to be inserted. Also the Challenger diff uses solid shim washers instead of perforated limited slip disks so you'd probbaly want to change those out.

https://fearlessrc.com/product/prcr0068/

Also the gasket is much more substantial:

https://fearlessrc.com/product/prcr0108/
 
So I now feel that the HD (25mm) drive cups are more trouble than they are worth, the larger cup requires limiting the down travel more to keep the axle boot from binding on the arm. Also a 5mm dogbone pin sounds like a good idea till you realize that the differential output gear pins are still 4mm. You can get 9mm shaft versions of the standard dogbones (they come standard on Rovan bajas) basically the same as the HD dogbone but with a smaller head to fit into the 22mm cup.
 
Fixing the flawed aluminum version of the Rovan symmetrical steering arm:

This is the original unmodified version:

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The problem is that the stainless steel flange bushing is over compressed against the washer by the spring which causes excessive friction and binding. This mod will fix that.

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Above is the original bushing, washer and spring, below is the new 10x14x10 (22x2mm flange) oilite bushing. 7x10x10mm stainless steel sleeve and m4x14x1mm brass washer. The m4 countersink washer is optional a button head screw would work fine. The flange needs to have the side cut off flush with the side of the bushing. Here I overdid it by about 0.3mm and ended up putting a flat spot on the side of the bushing however this will not affect anything as the bushing and spring rotate together on the steel sleeve. I have also polished the bearing surfaces, the top of and the inside of the bushing as well as the brass washer with 2500 grit sandpaper.

To cut the flange evenly I put a fiberglass cutoff wheel in a drill press and clamped the bushing in a bench vice, lined up the wheel to just above the side of the bushing and slid the vice and bushing under it.

baja_sym_steer_002.webp


Optional step, I fixed the sleeve to the shaft with retaining compound. If I need to remove it later I would use some heat and a gear puller to get it back off. While I was at it I also replaced the stock metal shielded 7x14x5mm bearings with proper rubber shielded ones. You need to apply heat to get the bearings out of and into the aluminum parts.

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Completed, the spring and bushing now pivots on the steel sleeve, the spring is no longer over compressed (the original flange catches and compresses the upper leg of the spring, the new bushing does not) and the friction between the flange and the retaining washer is brass on brass which combined with the oilite flange bushing results in much smoother operation than the original over compressed steel on steel friction.

EDIT: Also I will definitely replaced that chewed up screw. That happened getting it apart they really locktited that thing in there and I needed heat and some elbow grease to break it loose.
 
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So this happened

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Hit a pole with the rear wheel, stopped it dead and ripped the lower suspension arm out of the bulkhead and the outer part of the wheel off the center. It also caused some of the beadlock screws to partially come out. The parts to fix are cheap but it's the time to fix it that's annoying.
 
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I bought the stainless steel version of that:

https://www.ebay.com/itm/256528097370

One caveat is that it gets in the way of fitting a bumper, You still can but you have to cut the hook off and drill two new countersink holes in the bumper to hold it in place due to the lack of the hook, and use longer screws.

Also it can be fitted to a Kraken RC front chassis but due to the thickness of the angled part you would need an approximately 2mm thick shim between the wider horizontal part of the plate and the bottom of the chassis. This could be 3D printed easily enough and once installed you'd have a DOUBLE steel plate up front, one moulded into the plastic chassis and an extra one bolted on for a total of 8mm of steel up front.

Also in case you missed it, the Kraken chassis actually did survive that crash the plate didn't bend the plastic just got twisted a little too far and stayed twisted a bit along the length of the tub but could be twisted back by carefully warming it up a little with a heat gun clamping the plate in a bench vice and applying elbow grease to twist it back.
 
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Baja is fixed, the replacement rear bulkhead set I bought from Titracing seems to be made from nylon, vs the Rovan version which is made from some extremely hard and stiff composite. I'm not sure if this is better or worse but it seems up to the task, maybe the nylon would have resulted in less damage in the previous crash. "Make it stronger" is not always the correct answer. Also no hardware is provided, but the whole set was $6 so I'm fine with that I'd rather they just leave the unknown quality hardware out and pass the savings on.

HOWEVER the Rovan rear forward bulkhead has a completely captured nut for holding the shock tower support screws and the Titracing version has an open sided recess for that nut where it can fall out until the screw thread and nut engage. But the materiel the screw passes through is also 4mm thicker (it needs a 20mm long screw instead of a 16mm). So you need to install the shock tower supports before installing the rear forward bulkhead not after when it would be nearly impossible to keep the nut in place.
 
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Baja 5B with Kraken RC extended arms 1" wheel extenders and GPM X-Maxx reservoir shocks installed. These shocks have a 24mm shock body and 7mm shaft. No limiting straps are required the lenght is perfect IF you replace the front shock tower and rear shock brace.

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I needed to replace the aluminum shock ends with plastic HD Kraton 8S shock ends because the balls were not removable and would not fit in the suspension arms. The balls are 13.5mm wide and a 12mm wide ball is required. The Kraton 8S balls are cheap and 12.5mm wide which was easy to lap down to 12mm. Note that there are two different versions of the Kraton shock ends, the standard are for a 5mm thread and won't fit. I also needed to use the Rovan multi-mount rear shock brace the FLM V1 front shock tower. If I was using standard suspention arms then I'd also need to use the Rovan upper suspention arms for big mpree shocks, but the Kraken RC ones are already designed for big bore shocks. I'm using 3.25mm wire diamater springs in back and 2.8mm wire spring in the front. EDIT: Forgot to mention that the spacers that come with the FLM shock tower aren't wide enough for 24mm shocks. I used some different spacers I had laying around but if you were to use the stock ones that come with it you'd need an additional 2mm or 3mm thick spacer washer.
 
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