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But they go to gear diffs in touring cars and 4wd. That's a different story all together. I can try to make it more understandable with this statement though. It just as fast, but more unpredictable and harder to drive, on the plus side it means less maintenance. |
This makes me think of front one-ways for 4WD. When I started with 1:10 OR a few years ago, I got the impression that everyone used them. It was simply faster.
But when I finally tried with a front diff everything went way better for myself! Much easier to control, and I really cannot say that I got more steering from the one-way either. And MUCH better in the air of course. It's not always a good idea to copy the set-up from the very best drivers... unless you have out of this world hand-eye coordination, an easy to drive car is always faster on average! |
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I'm not sure about gear diffs in 2wd's. from what I have heard, ball diffs are more precise in 2wd. Have not heard of any AE team drivers using gear diffs. |
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Whilst some of the worlds best may be driving gear diffs...in 1/10th offroad there are certainly a lot of the top guys who are still on Ball diffs! The 2 UK National winners from 2010 are both driving ball diffs, and will be again in 2011 as far as I know! Sponsored drives aside ;), the top guys could drive any style of diff and make it look like the best thing since sliced bread!!! I'm really interested to hear this talked about...from an average driver point of view the gear diff looks like a good idea. But from what I'm hearing...only from a building/maintenance/reliability point of view! I'm really interested in running a durango for myself to see if I can tell the difference, so Razers comments on the lack of consistent driving feel are very interesting! Good discussion :thumbsup: |
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Well my durango is quite hard to drive compared to other 4wd's I have/had. Cannot put that down to the car itself or cos of the gear diffs. I have also heard of people using kyosho ball diffs in their durango's, so maybe you are right! |
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If I could just get my modded B44 diffs ready... I'd be really interested to hear how it feels to drive with gear diffs!
But there's guys on here that's tested gear diffs in their B44s, speak up! Gayo for instance! :woot: |
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this gear diff by specR, made for the tb03 'could possibly' fit some current offfroad 4wd's with some work.
http://www.spec-r.com/specrr2/module...roducts_id=108 I'm going to order a couple of these diffs, and see if they fit in some of my 4wd's eg. D4, zx5sp. |
Keep opinions coming, this is one of the more interesting threads for me in a while:thumbsup::thumbsup:
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B44 : I tried with the help of Olivier "The Brain" Langlet Durango diffs on my B44. I liked the adjustability, running stiffer diffs (specially front) helped to make the car less twitchy. Sadly the diffs leaked (solved now with Kyosho o-rings and good grease). As I fell in love with K-cars, I sold my B44 quickly. I sold the Langlet-made transmission to a mate (hey, I gave the money back to Olivier!) and he seems to like them on his B44. CR2 : I built my car with the Desert Truck gear diff. Franckly I found the car bad, a bit twitchy on carpet and hopelessly understeery on slippy indoor floor. Again I sold the car quickly but I'm afraid all the problems came from the gear diff. It was also badly made with very soft outdrives, not something I would recommend to anyone. So, to sum it up, I feel that to perform well and if you run on different kinds of tracks like me, gear diffs have to be tweaked to each track to perform best, so they actually give more work on the car, not less. They are also heavier and quite messy. I didn't feel they gave me any edge on track, so unless experience shows that a gear diff is faster, I will stick with ball diffs. Wow, lots of english words for me :bored: |
:cry:...
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On Tc Gear diffs are for the Mod racer running on large sweeping tracks at 65mph.
I tried one in my car and Its almost like a spool, I could muck about with different oils but a ball diff is much easier to tune (a slight twist on the screw) And if you make a ball diff properly they last for ages before maintenance on 10.5 or less. |
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High power brushless motors is what starts this problem. I remember running the TC3 in modified, and on a hot summer day with a 12 turn(european limit), I got about 6-8 packs of running through the original diff with plastic outdrives. And I remember the power as very good, it spun all four of my Sorex 36, fully sauced and heated. Try that diff now with a 3.5-5.5 turn, and you've come to a dead stop in probably two minutes.... I run an 8,5 turn in my 2wd, and my diffs last for 2-3 practice days on carpet. That is usually around 900 laps with high grip, and outdoors they last a lot longer. What I have figured out is that your balls and rings should match. I tried running ceramic balls, and they're great. Never wear them. But the rings get crappy in half the time because all the wear is on the rings, so the overall value of using ceramic balls is low. |
Yeah, I didn't make very good friends with ceramic balls either!
My experience is also that the diff lasts longer with steel balls. I also find it easier to adjust the diff with steel balls. It feels a bit on/off with the ceramic balls (too loose or too tight is very close to each other). And as I understand most UK racers just re-use the steel balls and only grind down the rings. Which must mean that even the steel balls don't wear. Never tried myself though, always replace the balls... |
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I was talking to someone this week about oneways - and they made a point I'd not considered and that's just the sheer power and speed of the cars might be too much for a one way now. A lot of drivers I knew running one-ways in years gone by have stopped running them. |
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Precisely. The biggest problem with one-ways today is the inability to brake. I tried one in my Tamiya 511 on a big outdoor track. At the end of the 50m, 105km/h straight (we had a speed gun) there was a hairpin. With the oneway I had to brake almost 20 meters before. With the diff I could get that down to 5 meters and 4 tenths on the laptime. Its the sheer amount of speed we carry towards the corner that dictates the need for brakes and the main reason oneways arent used anymore, at least not in the faster classes.
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Power = torque x revs. Strength of the system is a function of torque. Gas cars get their power through revs, so their systems can be smaller than electric cars, who get their power through torque. It doesn't follow that a system that works in a gas car will work in an electric car. A Veyron has twice the power of a 38 tonner, but if you put the driveshaft from a Veyron in a Volvo truck, the Volvo would snap it with one lift of the clutch! All that luvverly torque...! This is a great thread, full of interesting information. One thing I would be interested in is how you guys measure the torque limiting capability of the various diffs, and how you measure the percentage of lock-up. If this area is well understood, you'll be making good progress, and I'd love to apply your calcs to a 12th diff! As for Torsen diffs, I doubt they could be engineered into the space provided. However, a smaller version of the Ferguson fluid clutch diff should be possible - imagine a Losi Hydra slipper scaled down and popped in a diff and you get the idea. A clutch-based LSD would also be possible - imagine a PTFE slipper clutch popped in the diff to give you adjustable amounts of limited slip. If Cecil Schumacher is still up for a challenge, he could make a second living with a proper LSD for On- and Off-Road!! |
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I'd love to be able to run a one-way diff in 4wd, I'm sure I'd be faster over a single lap - but that's the problem. There's a much bigger chance I'll make a mistake on big stops into slow corners. Also a one-way has a bit of a mind of it's own accelerating through bumps in a shaft drive car, less of an issue on those rubber band cars ;) |
A 10th scale one of these couldnt be that hard to make.
http://tlcequipment.files.wordpress..../imgp1838e.jpg |
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I'm an experienced 1:8 TR driver, which is the fasted RC class. They do approx 110 km/h on the straight, and that's with super wide sponge tires, a 2-speed and a combustion engine doing 50.000 revs/min... I know touring cars are faster now with brushless and Lipo, and can show equal or better laptimes than 200mm. But a 1:10 OR being as fast on the straight as a 1:8 TR... sceptical... :D Very interesting about the braking! |
I do know that I would pay good money to anyone able to put Durango diffs in my spare FS2. PM me if you are that man.
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As I understand there's a guy in Germany that has made something like this for his B4- which works very well! But he wants to keep it a secret it seemed... |
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And remember to order replacement Kyosho O-rings (JE Spares carry them) Can those of you that know 1:8 OR list all the types of diff existing for those cars? Plus give a quick explanation of the "felt difference"? -regular diff -Torsen diff -Fiorini diff? ... |
have been messing with a plated diff, only at early stages really, no friction plates as in a full size diff, just relying on the viscosity of the sillicon oil to provide the limited slip effect, how it compares i cant tell you as it hasnt been put in a car yet, but it feels when rotated to lock up harder than just oil and gears under pressure
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have a look at the quaife ATB differential, that would be easy enough to minaturise, they work well too, ond mugen 1/8 diffs were laid out like this but not with helical gears
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I'm very skeptical towards a fluid based LSD, as I can't really see how that will deliver the precision we want in the size we demand. Of course, I do not know what technology active differentials from WRC 5(?) years back were based on, but in all my experience, a purely mechanical diff that can be preset as you like it, is a lot more predictable than any viscous and oil based solution. At least with available technology to be put in a 10th scale car:) But then again, I'm not familiar with all options, and I'm not an engineer:) |
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I had a couple of FF diffs in my Sierra XR4x4, and they were excellent. :confused:
Any of these diffs can be scaled to fit into a model, that's the easy bit. What you can't scale is the Laws of Physics, and they start to give different results when things get bigger and smaller. Those results don't always mimic in a model car what is experienced in a full-size car. The clutch-style LSD might not work correctly when the area on the clutch plates gets to be so small, for example. An example of this is the size of dampers we use. If a TC damper were scaled up to a full-size touring car, it would be so big it wouldn't fit in the space provided, but if the touring car one was scaled down, it would have so little fluid and movement it wouldn't work at all in a TC! That's the challenge, finding a solution that does what you want it to do. Simply looking to full size and trying to scale it is probably not what is needed. Something different is likely to succeed IMHO. |
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Was going to have a shot at making some durable diffs out of grooved race way thrust bearings but this LSD thing has got the old coconut thinking. one daft idea was to have a cog on each outdrive meshing into an idler and then to another cog that carries a slipper linking each side. It was the only manufacturable way within my means to do it as far as last nights thinking was concerned. Probably take up too much space and too much rotating mass. http://i471.photobucket.com/albums/r...gg538/lsd2.jpg |
Fun fact: My latest ball diff did about 350 laps on Thursday and 440 on saturday, on carpet, and it still feels brand new;-)
Also, the B-fast stuff gets a lot of good words, I'll be trying that soon... |
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We also need to remember the INSANELY big jumps our cars face! Only thing that slightly resembles an upscaled RC as I can think of right now are those Paris-Dakar buggies. They have very long suspension travel and can jump like a kangaroo :D Quote:
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-------------------------------- But guys, have you all read about this? http://www.oople.com/rc/photos/euros2010/day2/ Georg Kotzinger from Germany was running a pretty standard looking Associated B4.1 buggy - but we got a tip off about his unique gearbox which looks like nothing special from the outside. Inside however - he's got something pretty strange going on. The differential is a geared diff that he's been running for the past three years and ABSOLUTELY won't give away it's internal secrets to us mere mortals. The differential has the usual 'differential' action so one wheel will turn more around a corner but most of the time it locks or has a limited slip action. If the car lifts a wheel when going round a corner for instance, the car wont lose momentum and the wheel with the most grip (the one on the ground) will have full drive. Interesting - wish we could get to see inside! :( http://www.oople.com/rc/photos/euros...r/DSC_2215.jpg If any of you guys were there to see it... did it perform well or not??? Often hard to tell if these home-made solutions are good or not, as "mad scientists" like these seldom are the best drivers... :lol: |
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http://www.eaton.com/ecm/groups/publ.../ct_126000.jpg Shy, don't you read anymore? B-fast is mentioned for balls and rings every time someone complains about their balldiffs;-) |
Tell me more about that diff! Looks like a medieval torture instrument! :woot: Sure does look long lasting!!!
Only audio books these days! :thumbsup: Link please kiddo!!! Ovlov? Lada model??? :eh?: Btw got a 22 yet? Tempted to get one myself... Then there's this thing: Fiorini center diff ("torque reactive differential") http://www.rctech.net/forum/electric...tial-mbx6.html http://i46.tinypic.com/2ep2epu.jpg Would center diffs be worth having in a 1:10 car? Or why not vs. 1:8? |
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