Optima Mid Gear Slip HELP Please..

[BOARDRIDER 7]

My Optima Mid seems to build up speed slowly and struggle on grass although top speed is very quick. If I hold it still and accelerate gently the the motor and pinion are turning the gear but the belt is not moving. It feels like a slipping clutch on a car. Does anyone know what can cause this and how if at all it could be adjusted or if not what may have gone wrong?

[Barnoid 71]

What sort of Mid is it? LWB? SWB? Gear or ball diffs? Does the spur seem to move OK? Any melting plastic-y smells? Initial thoughts are that the spur 'slipper' (it's not really a slipper; it's too primitive) is loose, and needs tightening. Anything else will get time consuming, as it'll involve a near total strip down.

[BOARDRIDER 7]

Hi, its a swb not sure about the diff type. I haven't opened it up yet. There aren't any smells but there is a squeaky noise as it pulls away. I'll take it apart and get back to you. Thanks for replying.

[BOARDRIDER 7]

It was as you said, the spur gear was slipping. The rubbing had shred a bit of the surface of some of the layers behind it away but after a clean up, re-grease and tighten it seems to be good again. I'm not sure ill be able to find those parts anywhere! Do you know if there's an alternative to all those parts behind and in front of the spur gear? Thanks for your help.

[Barnoid 71]

Glad it worked out! I'm not sure if there are any direct new replacements for those bits, but spur parts do crop up on ebay from time to time. Another alternative would be to machine a longer shaft to install a modern slipper clutch - there are a few folks on Facebook who might be able to sell you one - but that's as much of a hassle (and an expense) as you'd imagine! My 'race' mid has an Associated slipper only so I can run brushless without fear of drivetrain death, but I think it'd be overkill if you're not planning on racing with brushless.

[BOARDRIDER 7]

I do have a brushless combo in it at the moment and I'm not loving the idea of drivetrain death! Although I'm never going to race it I think maybe I'll research these clutch upgrades to save killing it. It's going great at the moment though!

[Barnoid 71]

Find the Kyosho Vintage RC group and look for Rama Chandra - I got mine from him; it now runs an AE slipper :-)

 

[Wooders28 4719]

The best, most reliable option is to upgrade to a modern slipper, as above, (if I remember right) , it was a direct replacement shaft, and then used Team Associated parts (?) , they'll take more abuse ,and parts are easier to find!

I found a ,Schumacher K2 multi plate slipper can be made to fit, but requires a bit of welding and machining.

Another option is to look for replacement slipper pads, OT-88 protector plate , there's one on eBay the now, but a bit pricey for shipping to the UK...

 

 

https://www.ebay.com/itm/254629732377

Although, I recon you could find a bit of friction material ,and make your own? 

[bartman77 16]

hi ,,  Shapeways sell 3d printed gears too OT85 and SG25 ,, dont know if there any good  and was looking at ali express  for OT-85 (Flat aluminum alloy 0.8 mod 28t 29 teeth involute straight gear) they have ali gears that could be machined to hold the bearings 

https://www.aliexpress.com/item/4001015881811.html?spm=a2g0s.8937460.0.0.11b32e0eeM1Z8H

[bartman77 16]

https://www.aliexpress.com/item/4001015881811.html?spm=a2g0s.8937460.0.0.11b32e0eeM1Z8H    i spent hours looking   but i have fixed the diff problem   solid now ,, 

[Wooders28 4719]

On 7/4/2020 at 4:39 PM, BOARDRIDER said:

My Optima Mid seems to build up speed slowly and struggle on grass although top speed is very quick. If I hold it still and accelerate gently the the motor and pinion are turning the gear but the belt is not moving. It feels like a slipping clutch on a car. Does anyone know what can cause this and how if at all it could be adjusted or if not what may have gone wrong?

Not sure if it was you that wanted one?

But

There's a guy making another batch of slipper shafts, to accept the more modern RB6 slipper parts.

 

https://www.facebook.com/groups/IconicRCSales/permalink/2781685002072800/