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

I went back to the plain nylon c hubs and i think that's working better . I got dogged off with the constant failure of the one way roller bearings in the front drive hubs so i drew up and printed some direct drive ones instead .


Also printed up a CF nylon front bulkhead , shown next to the plain nylon one .


Had a couple more runs today and the gears are still going strong , should have time for another run later .
Its quite a learning curve working out what material to use where , the C hubs and chain sprockets are better in the plain nylon , suspension arms ,gears and gearbox in CF nylon , top deck / chain guide ,battery tray and wheels are all fine in ABS and just the rear chain guide in PLA .
These are my experiences anyway but it adds to the complexity when selling parts , if its a car that's going to get used a little , raced or displayed you might want different quality parts .... more to think about .

Managed to break two more bits today , probably in the same accident ,I landed a jump crooked and ran into the fence with the right front , it broke the right steering bell crank made as a slightly beefed up version of the original and printed in ABS and split the steering knuckle around the ball stud thread , it didn't let go completely , it was a direct copy of the original printed in plain nylon .
Both parts have had a redesigned part made up to replace them , hopefully beefing them both up significantly in the area they broke , both now printed in CF nylon although plain nylon might be better for the steering bell cranks as it flexes more , time will tell.
The transmition is still holding up well so I'm close to thinking that that's ready , the only under tested transmition parts are the stock chain sprockets , I've been running with a Kyosho chain and sprockets I modelled to match so at some point I'm going to have to rob the chain from my stock Dogfighter so I can properly test the sprockets I've made for it , I guess I should do that soon .

No breakages in two days , that's seven runs and I'm starting to treat it like any other car , I've cartwheeled it several times , run it into the fence a few times , I've got a little course set up with a jump , its not a huge modern jump and its on grass but I'm not babying the car anymore , the gears are as I want them and I've made some minor design changes that correct some fit/clearance issues so I'll probably be happy by the end of the month that its all good and well tested , that should time out well with having a second printer up to the same standard as my original one , after that I'll look at taking orders if anybody want anything .

Just been reading old posts on dying nylon , wonder how well it works on printed nylon parts , my wallet groans every time I think these days

Wish this lot was all genuine , its all development parts . I'm not obsessed

12 runs and multiple cartwheels ,crashes and bad landings and I've cracked a C hub , not fatally but its letting go , I don't think that's too bad , I'm treating it way rougher than my genuine car and bits break on that at a similar rate , I've modified the design again to strengthen the area and I'll print another pair , I need to start logging things properly .
If that's the weakest part then the Pargu store C hubs are not overly expensive .

As a side effect of test driving 3-4 times a day I think my driving is improving , I'm finding it much easier to line up on the jump in my garden , keep its attitude in the air and to keep it on the worn thin grass instead of the deeper grass ! I'm really getting into a groove with this car in a way I've not felt since I was racing my Hot Shot !

Dadio wrote: ↑Wed Sep 18, 2019 12:27 pm Just been reading old posts on dying nylon , wonder how well it works on printed nylon parts , my wallet groans every time I think these days

My printing company offers it as an option. And ORB delivers dyed parts too

Mr. ED wrote: ↑Sun Sep 22, 2019 3:37 am

Dadio wrote: ↑Wed Sep 18, 2019 12:27 pm Just been reading old posts on dying nylon , wonder how well it works on printed nylon parts , my wallet groans every time I think these days

My printing company offers it as an option. And ORB delivers dyed parts too

Thanks I'll give it a try .

Had a couple of parts failures today , the front chain sprocket ( Kyosho chain ) stripped and the idler gear in the gearbox started slipping , they have both been on and working for 30+ runs and I have just fitted a brushless motor and run lipo , all the testing till now has been with a 19t brushed motor and 2200 mahr NiMH battery , I'm not sure what to think ,weather with brushed power it would have gone on or if this is an acceptable service life , my feeling is that all would be well on brushed power and that brushless was just too much ,I don't think I can make stronger gears , thoughts ?

It's interesting that it was the front sprocket that failed - is the rear sprocket metal?
Can the tranny gears be made in a higher mod to increase shear?

depending on the wind of the brushless motor, the culprit might well be the lipo. it's lighter than nimh, but it runs like a 7 cell pack nicd for almost the entire drive time. nimh has a higher internal resistance, so it's not as powerful.

XLR8 wrote: ↑Tue Oct 01, 2019 2:29 pm It's interesting that it was the front sprocket that failed - is the rear sprocket metal?
Can the tranny gears be made in a higher mod to increase shear?

The front sprocket is printed flat , the layers are in the strongest orientation so its not layer separation . The rear sprocket is printed also so I have no idea why it survives , strangely when I was running test PLA sprockets its was the front one that failed , it may also be that I'm running no one way roller bearings on the front just direct drive with no diff , that may also be putting more stress on the front sprocket .
The Motor is as far as I can tell about a 10.5t brushless , its a motor that came in a RTR Team C car I own and the battery is a 2s 2600 mahr 90C shorty pack , its for sure way more powerful than the 19t brushed motor and I'm running it on grass so a lot of traction .
My feeling is that run on even a low turn brushed system then the transmition would last a lot longer ,I put the BL into it in order to speed up stress testing , I guess I went too far .

I think Joe makes a good point, it's not just the motor that is creating more drive-line stress, it's the lipo battery as well.
I've never owned a Dogfighter so I don't know but if the gears are say .8 mod, raising them to 1 mod should increase the strength of each tooth. Is this possible?

Changing from 0.8 mod to 1 mod might solve the problem but I really wanted reverse compatibility , the other thing would be the math , would 1 mod gears fit with the spacing inside the gearbox .... Probably not so I'd need to alter the gearbox as well ..... Again no reverse compatibility , I'm going to open the box and have a look tomorrow but I'm pretty sure its the idler gear , its actually on its second life anyway as earlier the shaft had slipped through the gear and popped out of the bearing on one side , that did surprisingly little halm to the gear ,for all I know it might have happened again , if its just the shaft slipping through then I'm laughing , I'd just put a knurl on the shaft and press it in next time but I think its likely that the gear has worn .
I'm fully aware of the difference in battery's from lipo to NiMH , although I've only used lipo in cars for a few years I switched from NiMH to lipo in airsoft guns over 10 years ago , I'd wanted more run time for testing so I wanted to use lipo , that also meant the switch to brushless as well because the brushed motor was pretty hot after a run with the 2200 mahr NiMH , it would have been glowing after a run with the 2600 2s lipo . I used to run my stock Dogfighter with a 17.5t brushless system and my highly modded Dogfighter runs a sendsored 10.5t but it has a slipper so its gears are protected to a degree .