RC10Talk - The Net's Largest Vintage R/C Community

On eBay, there's a set of Parma carbon rear axles, but I don't know that it would give enough weight reduction to make much difference. I think the gearbox configuration is the limiting factor. Maybe something could be done with softer compound rear tires to absorb bumps better.
.

Frankentruck wrote: ↑Tue Jul 26, 2022 12:06 pm On eBay, there's a set of Parma carbon rear axles, but I don't know that it would give enough weight reduction to make much difference. I think the gearbox configuration is the limiting factor. Maybe something could be done with softer compound rear tires to absorb bumps better.
.
Screenshot_20220726-110240.png

I was actually thinking of taking the axles out and putting them on the lath to thin them down a bit between the bearings , there's quite a substantial metal shaft that the spur gear runs on that I could replace with a piece of CF rod I know I have as well , the gear cover that's held on by the motor screws could be replaced with a bit of Lexan , the oil fill cap and screw could be replaced with a dab of silicone sealant , the three piece wheels are probably not the lightest either , the list of little things is quite long but each one offers very little really .

It would all add up, but it all could also reduce the durability. But if there's a Grasshopper Invitational race series, having the cheating-est Grasshopper entered could be worthwhile.

I just weighed the wheels , 67g for the Tamiya wheel tire combo , just weighed a modern buggy wheel n tire 46g , that's a big saving of 42g for a pair

Those carbon axles are cool..but I don’t think those and other minor lightening will help much. The big problem is the heavy motor. Softer tires would probably be the biggest help.

Just out of curiosity I weighed the whole caboodle , 450g so shedding 40g from the wheels is not negligable but I can't see me shedding near to another 40g , maybe another 20g ? That would be over 10% loss , might help .

Motor is 154g by itself .

Are the current wheel assemblies air tight? If the tires have to stay inflated like balloons, that would add rear end bounce on bumps.

No the hornet/super champ tires have an air hole so they are not pneumatic .

Made adapters for 12mm hex wheels , fitted the FC axle for the spur gear , made a light weight pinion gear cover and replaced the oil fill cap with a small piece of Lexan . That's 52g reduction or a tad over 10% , it's pitch dark now but I'll give it another test drive in the morning .

Just found another 4 link mod on YouTube with some running footage , he added 200g of weight to the rear of the chassis and despite the heavy use of slow motion footage you can still see it hopping , he had also flipped the axle so the motor was at the rear , this makes no difference to the hopping but it does allow a lot more suspension travel so I might try it , with the greater articulation of the 5 link system over even the Hornet getting the clearance is difficult .

Just gave the new lighter setup a test , not really any better to be honest , the modern low profile 2.2 wheels are a lot less weight but also have very little squish in the side wall , overall I'd rather have the more squishy old school tires as it's kinder on the axle , may try printing a one piece lighter wheel for the old school tire to try and get the best of both but it's going to be very marginal in any gain , I doubt I'm a good enough driver to notice it .
On the bright side I could see the suspension moving relative to the body even at full chat so it's not torque locking the rear suspension , I have a sneaky feeling that the original suspension as it pivoted from a single point actually reduced the unsprung weight as the area of the gearbox nearer the pivot was not moving much where as with the 5 link it all moves the same amount ?

Just found some BL 2440 motors on eBay that are a direct swap for the 380 motor and they weigh in at between 50 and 68g , less than half the weight of the 540 at 154g potentially losing 100g and that's a worthwhile number .

Ok more fiddling , I stuck the old 380 motor back in and had another go , much more composed and pleasant to drive , I then tried switching back to the hornet rear wheels and it was noticeably worse so maybe that concludes the question of lighter weight over compliant tires , also suggests the BL 380 size motor might also be a win . I'll pop another video up in a bit .

Footage with 380 motor and modern wheels , this takes the overall weight down by 150g and the ride is more composed .
https://youtu.be/C-rRSCOkrE0