Ball Diff vs Gear Diff

I noticed that my Mid does not work well with gear diffs on loose sandy low traction surfaces , which cause the car to spin out on power while cornering.

On muddy surfaces or grass, the gear diff works great. So I decided to switch back to ball diffs, for this coming 8th Feb 2015 race. One of the problems with the ball diffs is it gets gritty by 10 packs, and you have to open the gearboxes and rebuild the diffs. There are 2 main causes of the diff getting gritty so quickly, one is dirt getting in the drive line, and the other is, even  if there is no dirt, ball diff greases break down ,turn black and form deposits. I recently bought a synthetic grease from ACE hardware ,called Super lube. I am now using this as my ball diff grease, and I will seal the driveline properly. In theory this grease will take much longer to degrade.

I opened my driveline yesterday and discovered sand in my gearboxes, and traced the entry points to the front belt cover edges. The front lower belt cover lifted from the chassis, and the one under the upper deck has also formed a gap. since the rest of the belt covers form a rather tight seal, when the belt moves, it forms a vacuum of sorts that sucks the sand inside.
I am now rebuilding the LWB with synthetic grease in the ball diffs and will reseal the driveline, hopefully I will succeed ,and get back the awesome handling as seen in the video of the last post. I want to get my LWB working to a level that it can challenge the Durangos and ZX6s.
Last night, on the 21st Of January, I rebuilt my LWB driveline, and I find the diffs to be smoother compared to before, thanks to the SUPER LUBE grease.
I set my front diff noticeably tighter than the rear, with the rear slipping a bit. I did this to make the car stable on acceleration and braking. This will make the car understeer a little, a car that understeers a little is easy to drive under pressure. Right now I use 10 Degree ZX5 caster blocks, and find steering to be a lacking at the very tight turns, may go back to 7 degrees depens on this weekend's testing.

11-Nov-2014, all paid off !

The car was incredible with the 7 degree caster blocks. I was finally able to drive it really well and keep with modern cars. The tail wasn't swinging anymore.

 

Adding caster to front

I have changed back to ball diffs, because the geardiffs don't seem so smooth. Since I did not have enough parts to rebuild a rear ball diff, I made some improvements to the standard kyosho rear ball diff.

I got a 8x16x5 bearing, and got my machine shop to make a 16mm sleeve with 19.8mm outer diameter.


 

The bearing slides into the geardiff casing

 

This ball diff is now very smooth.

I also used Lazer ZX-5 7 degree c hubs with 3racing ver2 ZX-5 alloy knuckles. I had to grind the c hubs in the fronts to make sure it will fit into the arms without binding. I am in the process of making a ZX arm that will be a direct fit with ZX-5 c hubs.

7 degree caster blocks with 3 degrees in the arm mounts equal 10 degrees total. this should improve handling. However I find that steering throw is also reduced.

Assembled parts. The front CVD is 3racings 65.5mm and upper turnbuckle is now 50mm.

                                   

Grind the c hub below the angle mark. With my new arms which will be ready next week, no modifications will be needed.

 

Turbo Optima Mid SE SWB test run for racing

Bashing on the Beach

 

 

 

Ready for racing - 2014

After cleaning up. Some sand went in the front gearbox and made its way to the back. I changed new gearbox so that it will hold better on the chassis.

Serviced LWB next to my SWB

Built a SWB Optima Mid - finally !

This was my brother's old Turbo Optima Mid, that was in pieces.
I have a LWB ,but I missed driving a SWB, so I decided to rebuild one with some upgrades.

My Own Made associated B4 slipper compatible layshaft. More is available for sale.

The loose parts layed out

 

The front & rear ball diffs and rear gearbox innards. Notice my own made hard PEEK gear. I have more for sale.

Semi completed

Assembled gearbox and slipper.

With 2.2" wheels

Kyosho GP10 strong steering parts.

Incomplete rear end

Grinded arms, flipped, to make sure CVDs exit straight

semi complete

Recently completed with Mid SE decals

http://www.youtube.com/watch?v=QrZf_AYY0og

 

This is a video of this car running, hadn't had a chance to test it offroad yet.
After the ball diffs get gritty I will install gear diffs to cut down maintenance.
next build, my Old Lazer ZX !

Raced my mid today

So finally there is a EP offroad race in MYMTRG track. Unfortunately there wasn't enough entrants so all the EP 1/10 rc vehicles had to be raced together. In the field were 2 Durango DEX 410s, 2 Losi 22s, and one 2WD SCT. On Saturday, the track was mildly muddy, so I decided to use OT-66 tyres. It wasn't a really good race as I did not have any practice these last two weeks. The car kept overturning easily in the ruts as it seemed like the spikes were digging in too much in the bumps. However I finished the race without damage to the car, except the gear cover. I managed 5 laps in 5.08 which netted me in 3rd place for the first heat. Suddenly my boss called me and ask me to haul my butt to work. So I had no choice but to leave the 2nd and 3rd heat. Sure enough some one else beat my time and I slid down to 5th.

On Sunday, I used Lazer ZX-R tyres, figuring that the track was still damp and the hard spikes will dig in well. In the first final I did not do so well, but better than Saturday. I still made 5 laps , and cut down my time to 5.02 which netted me a 3rd place behind a TLR22. Still not happy with the car overturning, I increased negative camber on all 4 wheels, I surmise this would help prevent the car from overturning in the ruts. I also tightened up the slipper clutch to gain more speed and changed my driving style to go easy on throttle coming out of the corners, then gradually increasing speed. It paid off in spades and I cut down my best lap time down by 6s. I also finished 6 laps this time. In the 3rd heat I manage to repeat my performance. 2 finals were tallied and I won 2nd place behind a DEX410 driven by a young guy name dragon. I was really happy with my Optima Mids performance , and the new arms and PEEK c hubs I made were really strong and did not fail even though I took some pretty nasty hits. The Optima Mid has gained the respect from the newer generation after this race. The young guys were surprised with its performance and silence. 

 

 

 

Gear Diffs Yet Again

My rear ball diff failed on me last sunday while batting a Durango DEX410, embarrassingly. I really believed I could have at least  kept up with the DEX410 if my diffs were working. I am now installing gear diffs in my MID. I used Xray TC 300,000 gear diff oil filled only half. I did this to make sure the diff wont unload too easily and also the pressure in the casing will not be too high and cause the oil to leak out. I tried this and the diff is quite hard but still movable. The silicone oil should ensure that the setting remains constant and wont loosen up. For the front gear diff I used RIDE TC putty, to make the front diff almost like a spool, just the way I like the car to handle, very stable.
I will let you know how it goes. I hope the large bevel gear will not separate out from the shaft, or I would have to take the car apart yet again...

Latest updates and changes-Back to Lazer ?

I just recently got a new batch of layshafts , and I haven't been running my optima mid since last year, when I sold my layshaft to Daniel Rowlands. My car has been running for some time now with the optima mid suspension, with the back arms flipped so that I can place the shocks behind the wheel in order to clear the layshafts.
Last night while I was looking my car over I noticed that the rear CVDs were exiting the diffs at an angle, it was swept forward. That means the wheelbase was also reduced about 5mm. There was also noticeably a huge amount of rear toe in, which isn't really a bad thing.
However, the forward swept CVDs could pose a problem.
Forward swept CVDs will pull the rear suspension down under acceleration, and rearward swept will push the rear up, both conditions are not good for optimum handling. I did find my rear end washing out every now then. I then tried placing back the Lazer rear arms, and sure enough, they exited straight as an arrow. If you remember , I had problems with snapping my Lazer front C hubs, so in order for me to use back the Lazer arms, I had to find stronger alloy c hubs. An idea just came to me, why not find drift car alloy c hubs, since touring and drift cars uses smaller components similar to the lazer and optima, I am bound to be able to find one that fits, then I would have to use the knuckles  that fits that c hub.
The MPP arms seem to be tougher than Kyosho arms, simply because MPP arms are more flexible. I don't know how that will affect handling, but for sure my car will be more trouble free. I have been hearing from other people in the know, like terry sc who swears the Lazers suspension is much better than the Optimas on rough tracks, so that's one of the reasons I want to switch back.
However, I did find a peculiar thing comparing lazer and optima arms. The shock mounting holes on the lazer arms are much further outwards. I believe they did this to get back the same wheel rate as the optima since Lazer arms are much longer and will give more leverage. Still I wonder if the wheel rate on the lazer arms is enough for rough tracks, as I believe the optimas shock positioning should give a softer suspension which will handle bouncing better. well, time for testing then.

Another thing I found out about kyosho big bores is the kyosho rod ends seem to be rather weak. I used X ray T2 touring car rod ends with their balls and they are much tougher, but they cannot go into the lazers capped arm because they are 5.5mm wide, compared to the kyoshos which are just 5mm. Anyway, I will try using back the kyosho pieces but this time I wont be removing them so often, and will put threadlock on them.
I will keep you guys updated on my front c hub findings.

Back to the Optima (suspension)

Ok, i love back to the future, since it was so 80's. So thats how i came up with this title. I was supposed to race my Mid in a race last week but i broke one lazer ZX front c hub while casing a big jump. I got so fed up and went back to the original Optima Mids suspension. One of the biggest reasons was i had  a pair of A & L alumimiun C hubs with bearings and i think i could practically bulletproof the suspension with these c hubs.

The A & L C hub, with 4x8x9x3 flanged bearings.
Thats a ZX-5 plastic knuckle. i ground off 2mm from the top of the knuckle to be 20mm then only it could enter the c hub.

another view.

Rear Optim Mid Suspension with the arms flipped so that i can place the shocks at the rear like the lazer. Thi is done so that i can clear the new layshaft .

Position of shock on shock tower.

I tried the car today on the terrible offroad track and it was much better than before, simply because i removed the durango shock boots that was interfering with smooth suspension movement. the Mid could clear the big jumps most of the time and landings were good. It also handled the bumpy sections rather well. Of course the tree roots still posed a problem, but the car was definitely better. Also since i was using modified kawada touring car knuckles, the mounting for the kingpins was too short causing the kingpins to dislodge itself and ending my testing. i went home and then decide to grind off the ZX-5 knuckle by 2mm at the tops so that i can slide it into the c hub.The zx-5 kunckles felt a lot more secure, and the kingpins felt secure in them too. i think i pretty much nailed this problem with this solution. will test again the next week.