Carsnz123 Posted September 7, 2017 Share Posted September 7, 2017 So the short version of this story is my brother and I compete in a vintage sporting trials event every year. Our car is a 1926 Pontiac. The problem is the car is big and heavy and we have to get creative as far as making it competitive against the likes of Austin 7s. Unfortunately in the rules you're not allowed to run a welded or limited slip diff. So has anyone got a good plan to make the spider gears function less. I was thinking of putting really thick oil in it or Penrite steering box lube. Quote Link to comment Share on other sites More sharing options...
tortron Posted September 7, 2017 Share Posted September 7, 2017 Can you run one of those preload things that were mentioned on here a while back? I think @rustisize used some washers to pack somrthing out too Quote Link to comment Share on other sites More sharing options...
tortron Posted September 7, 2017 Share Posted September 7, 2017 Search phantom grip. Could probably make something like it up Quote Link to comment Share on other sites More sharing options...
Yowzer Posted September 7, 2017 Share Posted September 7, 2017 You could pack it chocka full with grease and I doubt you'd feel a difference. I think your best bet is to shoehorn a Torsen in there somehow. Unloaded they behave like an open diff so ya might get away with it for longer. Quote Link to comment Share on other sites More sharing options...
Yowzer Posted September 7, 2017 Share Posted September 7, 2017 6 minutes ago, tortron said: Search phantom grip. Could probably make something like it up Google suggests you should have some spare diffs in stock if you use those. 1 Quote Link to comment Share on other sites More sharing options...
Nominal Posted September 7, 2017 Share Posted September 7, 2017 If the rules specifically so 'no welding' then there's nothing to stop you locking the spider gears by non-welding means. 2 Quote Link to comment Share on other sites More sharing options...
BLIZZO Posted September 7, 2017 Share Posted September 7, 2017 i cant see a way around it tbh, making something like a phantom grip is still technically a limited slip diff, the rules are obviously there for a reason. anything you do to make it lock under load is limited slip. Just run it as per rules. Quote Link to comment Share on other sites More sharing options...
Yowzer Posted September 7, 2017 Share Posted September 7, 2017 Rules are made to be broken 2 Quote Link to comment Share on other sites More sharing options...
BLIZZO Posted September 7, 2017 Share Posted September 7, 2017 yea showing a written copy of the rules might help answer this question, often in motor sport they state what you can do, not what you cant do Quote Link to comment Share on other sites More sharing options...
cletus Posted September 7, 2017 Share Posted September 7, 2017 Are you allowed individual wheel brakes? 8 Quote Link to comment Share on other sites More sharing options...
Hemi Posted September 7, 2017 Share Posted September 7, 2017 I nearly got into a table throwing debate with an apprentice once re: lsd's he was ademant that you could shim a viscous unit, no matter how hard i tried to tell him by shimming the unit it was just going to load the spiders he went " nah to locks them bro". so yeah. grab a sweet hardened washer and pack it out. Dawg. The rules no doubt have something about doing this though. Quote Link to comment Share on other sites More sharing options...
Alfashark Posted September 7, 2017 Share Posted September 7, 2017 6 hours ago, cletus said: Are you allowed individual wheel brakes? Should be sweet, do a search for fiddle-brakes - most of the vintage trial cars in the UK use them. Quote Link to comment Share on other sites More sharing options...
Ghostchips Posted September 7, 2017 Share Posted September 7, 2017 My diff had spider gears inside a 2 piece housing. By putting hard fibre washers in there (they put pressure on each end of the axle shaft where they meet at the center, acting as a clutch with a 1 inch diameter) it limited the slip, at least until the washers wear down a bit. Have heard of putting lead around the spider gears, easy enough to remove later if you pull the diff' apart, and no welding, so no harm done. Won't break your axle shafts either. Quote Link to comment Share on other sites More sharing options...
Popular Post fletch Posted September 7, 2017 Popular Post Share Posted September 7, 2017 You take the spider gears out and machine a tapered bore into them. Then you make some tapered cones that sit over the spider pins out of brass/bronze i forget exactly the best stuff. You size the cones so the spider gears are pushing towards the centre a bit. You need a bit of clearance - around 2or 3 mm between the back of the spider gear and the housing. When you spin a wheel it loads up the spider gears and they push out onto the cones and bind up. Its a bit of trial and error to get the taper correct to get good lsd action vs cone wear AND getting the spoders to free up once the load evens up again. Works best on a 4 pinion diff cos more spiders. The officials had a little roller that you drove one wheel onto to make sure you didnt have lsd or locker. You had to give it a gentle rev so as not to load up the spiders, then pump the brakes to get off. Never got sprung. 10 Quote Link to comment Share on other sites More sharing options...
ajg193 Posted September 7, 2017 Share Posted September 7, 2017 Just do the individual wheel/differential braking. Otherwise you'll probably end up getting caught and banned from the fun. For bonus points make the left seat person control right brakes and right seat person control left brakes. Also, can you fit tractor spec tyres to it? 2 Quote Link to comment Share on other sites More sharing options...
Unclejake Posted September 8, 2017 Share Posted September 8, 2017 I haven't read the thread, but the common way when I was racing was to shim the diff to make it super tight. Google should help Quote Link to comment Share on other sites More sharing options...
igor Posted September 8, 2017 Share Posted September 8, 2017 7 hours ago, ajg193 said: Also, can you fit tractor spec tyres to it? Yes totally fit farm service lug tyres. They work for me. 3 Quote Link to comment Share on other sites More sharing options...
igor Posted September 8, 2017 Share Posted September 8, 2017 Bit noisy on sealed roads though. Quote Link to comment Share on other sites More sharing options...
smokin'joe Posted September 8, 2017 Share Posted September 8, 2017 don't the streetstock guys fill the diff with either brakefluid or ATF to get them to bind uinder acceleration, whilst still being open while on the test rollers ? Quote Link to comment Share on other sites More sharing options...
Carsnz123 Posted September 8, 2017 Author Share Posted September 8, 2017 can't run mud tyres or fiddler brakes. They pretty much limit you to pre 1960 stuff that road cars came factory with. Quote Link to comment Share on other sites More sharing options...
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