Where would you track-build to solve this?

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L2SFBC - Robert Pepper - auto journo

3 ай бұрын

#trackbuild #trx4 #traxxas
So the TRX-4 can't make up and over. Where would you trackbuild to fix this?
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Пікірлер: 43

@Gemini_0815 3 ай бұрын

Acceleration of the free spinning wheel requires torque coming from the diff due to the inertia of the wheel. That same torque is then applied to the other wheel, because that’s what an open differential does.

@madautodetailing6691 3 ай бұрын

Tough one. I'm leaning towards A the most. Due to the setup of the model car: 50/50 weight distribution, 50/50 front/rear torque split and low COG. Weight transfers to the RHS instead of weight transfer to the rear axle. Maybe we're all right.....or maybe we're all wrong.

@thabzmoyo96 3 ай бұрын

D - the car has enough flex to put the power down and start climbing the first part of the obstacle but not enough to completely get over. Option D minimizes the height difference at the top of the obstacle with the rest of the difference is being made up by the flex of the vehicle. Option D is the best bet and if that doesn’t work none of the other options will because ultimately the best way to get over that obstacle is a combination of option C and option D

@MegaLaurentd 3 ай бұрын

It's the passage of the second step that seems to be the problem. It's hard to tell from the camera angle! You can't really see the difference between the position of the wooden blocks between themselves and the wheels. A- This transfers weight back to the rear left and front right wheels when the front axle passes over the second step but the rear axle will be blocked when passing over the second step as for the front axle or the wooden block would have to be repositioned. B- Does not change the situation C- Could work, but if the piece of wood is too short, as soon as the front right wheel has passed it, we risk having the same problem as initially when passing the second step, with the right front wheel hanging.With a bit of momentum, this could help. D- If the D position is too far away, which seems to be the case, it won't work. If the right wheels reach position D before or when the left wheels pass the second step, this could work. So let's say C!?

@UberCon 3 ай бұрын

The spinning wheels rotational mass causes resistance, which will transfer torqto the other axles, which I would think

@proudbugowner 3 ай бұрын

Thanks so much for all the informative videos! I would choose position C with a little more speed, but I'm a newcomer 😂. Regarding the open diff, maybe the wheel with more traction gets the additional torque required to increase the rotational speed of the wheel with less traction and given the lightness of this car, it is adequate to propel it temporarily a few centimeters.

@grantm1891 3 ай бұрын

Moves up the ramp as you are increasing torque. So the slipping wheel gets more.

@user-wx2el5jy2t 3 ай бұрын

I think it works because when the differential receives enough power it cannot put more on the wheel that is slipping so it gives what is excess to the other wheel

@davidberry2542 3 ай бұрын

C overall best. A & C will have a similar effect in reducing the angle between the diffs for the first obstacle but C will help a lot when you get to the second obstacle by flattening things out and that the rear will be overall higher as the front climbs the second obstacle which means less effort required. For the second question, when you accelerate the wheel, there is an increase in torque to both axles during the period of acceleration, which means more torque going to the wheel that’s not spinning. Once to acceleration is complete and the spinning wheel is at its new constant speed, the torque to each wheel drops back to the torque required to maintain that speed, and the car rolls back down until it finds the point of equilibrium.

@LesNewell 3 ай бұрын

Exactly what I think would happen. Very well explained.

@UberCon 3 ай бұрын

C 1st, but A after you engage, the obstacles would do it

@kienanmaxfield6288 3 ай бұрын

A would work for getting your front tires over the first obstacle, but you’ll be totally stuck at the second obstacle. Even without the second obstacle, the rear tires still need to get over the first one. I don’t think B would do any good really. So that puts us at C or D. I don’t know but I bet that the biggest factor is how it interacts with that second obstacle as I’m thinking that either location would get you over that first one… For the second question, inertia and friction. Everything has frictional losses, so the gearing that makes the free wheel spin will cause the other wheel to exert a small amount of torque because of the friction in the differential. Additionally, the inertia of the tire, wheel, & axle on the side with the free wheel will resist acceleration which will apply some force on that other tire.

@btlepyromane1648 3 ай бұрын

I guess position C beacause B seem usless D hard tu use without a lot of momentum and A will make the car will lean a lot. For the second problem, I guess maybe because of friction in the differential. anyway I crave fore the anser now. good vidéo

@andreas.9582 3 ай бұрын

Solution A would only be useful to let the front axle pass the first obstacle, so I think it's not the right answer. I would say C, considering the wheelbase and the distance between the first and second obstacle (just a rough estimate as there's not a side view of the ramp in the video). Provided the measurement explained above is right, the rear wheels would be still on the flat part and evenly pushing when the front right wheel approaches the second obstacle. Then the front left wheel would start spinning as the opposite wheel climbs to the higher part of the obstacle but at the very same time the rear wheels would be leveled on the lower part of the first obstacle (with the track in position C), so granting enough push before the rear left reaches the higher part of the first obstacle. When this happens, the front right wheel should have passed the second obstacle and leveled with the opposite wheel, so granting traction on the front axle. If it's not enough, while the front left is still spinning I would use the trick of giving full throttle for a while, as for the second exercise that led to the second question. The differential will not appreciate but it will make the difference between being home for dinner or doing some extra work in the darkness. 😊 Just can't wait to see your next video. 😎 Greetings from Italy. 🇮🇹

@neutronstorm 3 ай бұрын

Your right that A would get the front wheels past the obstical and was that the original question? There are more obsticals up the track that I think the vehicle will get stuck on no matter which of the options you use.

@dtnicholls1 3 ай бұрын

C. First, it flattens everything out at the point where it would be getting most crossed up. That puts more weight onto those two wheels, giving more drive. Second, when you hit the second lump on the left, you'll have more weight transferred to the rear of the vehicle, giving more drive to push up over that as well. Of the two, the greater benefit is just in getting the diffs flattened out. In that A is also a viable option, until it comes time to get the rear diff to climb, and it assumes the position works out just right with the wheel base, hence C is the better one. B and D do nothing to benefit traction, B just moves the point where you climb first, doesn't help with the second lump, D doesn't climb till you're already on top of the second lump and the issue is getting to that point in the first place. The only way D helps is if you're sideways across the hill which is bad and basically turns it into C anyway. As for the second question, the thing that's limiting the torque to the wheel with traction is the opposing force on the other side. There's a bunch of dynamic components to that caused by the oil in the diff, windage etc that are non-linear. The faster those components are spinning the more drag is present, which causes a greater torque to be applied to the side with traction. Don't make a habit of doing that, the small spider gears in the diff really don't like it. They're not designed to operate at high rpm, if you do that to them continuously they'll heat up and fail and if you do it intermittently they will wear excessively and fail. It's just a bad idea. Pull out the shovel or pack rocks instead.

@StefansView 3 ай бұрын

Thanks for this interesting riddle! I would build at position D. It helps the front wheels over the first obstacle (allowing some torque for the front right) while also keeping the car more leveled. That also helps with traction for the rear axle. When moving further up D again helps the rear wheels and hopefully the car will make it over the last obstacle. A and B would not help with the last obstacle at all. C would still have the car crossaxled after dropping down from C during the climb.

@neutronstorm 3 ай бұрын

The spinning wheel has inertia so when the torque from the motor changes, some torque is transferred to the ramp wheel. As the spinning wheel slowly accelerates, this equalizes the situation and the torque at the ramp wheel drops back to zero and the vehicle rolls back down the ramp.

@nirfz 3 ай бұрын

No experience in offroading, i would think position A and C would both work. Because in both cases the diagonal articulation needed is lowered and so all 4 wheels touch the "ground". In A because teh whole left of the car is on the obstacles and the right of the car isn't. In C because the front of the car needs less articulation and the back gets more weight transferred. In position B and D i would think this won't work: in B the problem without the additional piece of wood stays the same, and in D it's "too late" and the car doesn't get there. As for the question at the end, my answer would be: inertia? (as a non native englishspeaker, not sure that's the correct term) The increase of the revs is so quick that the inertia of the spinning wheel keeps it from accellerating as quickly as the reves.->The overall torque increased very fast with the revs and due to inertia, both wheels accellerated the same amount for a very short period of time pulling the car a bit up the ramp.

@hoyks1 3 ай бұрын

To keep the chassis relatively level left to right and help the front wheels get over the obstacle, I'd go position C. It will also help the rear stay relatively level and push over the next obstacle.

@OFFtheROAD34 3 ай бұрын

A: Traction on all 4 wheels!

@neutronstorm 3 ай бұрын

That's what I thought but as others have commented, won't you become cross axled again as your back wheels go over the obstical?

@neutronstorm 3 ай бұрын

I think i would pick A. This eliminates the cross axle issue. B looks like it just moves the problem down the hill, D the car probably wouldn't even get that far as its stuck on the original bump. C would be second choice however you then basically have a rock step which will be hard to drive and possibly high center your vehicle. A is the clear winner or pull out your shovel and get rid of the original obstical 😂

@neutronstorm 3 ай бұрын

Also, with C you're probably going to get cross axled when you pass C and the original slope will still be lifting your wheel. Other option is the drive to the left and put both wheel on the obstical.

@brunoterlingen2203 3 ай бұрын

Ripper, let the student think for him/her self, well done Robert.

@grantm1891 3 ай бұрын

D for me. Minimises relating axle angles on average over other options.

@StefansView 3 ай бұрын

Exactly what I think in a short sentence! 👍

@25052007 3 ай бұрын

As the wheel spools up torque is used and C

@Gemini_0815 3 ай бұрын

I changed my mind. This is more complex than I initially thought. It’s probably a or c.

@overlandready 3 ай бұрын

I would probably trackbuild on C, as it gives a good possibility of equalising the suspension travel and the cross axle issue. The reason the car moves up the ramp with open diffs and accelleration is friction. Friction internal in the diff, the gears cannot run absolutely freely so there is drag caused which effectively gives an action of a LSD. Can I also pull you up on saying "at one point the back end scewed around there" can I ask why you didn't call it understeer or oversteer? As that is exactly what you normally call it. That explanation should set you on the course to understanding why skidding is not over or under steer.

@L2SFBC 3 ай бұрын

I didn't call it understeer as the front end wasn't moving, but yes the rear lost traction and the car was yawing so I guess it's a form of understeer, but not what people typically understand by the term so I said it slewed around. I forgot to add this example kzbin.info/www/bejne/rGLaf6WchqytZtU

@overlandready 3 ай бұрын

@@L2SFBC This is my point on the whole misconception of over and under and neutral steer, if it physically did that movement, you 'd be right but it's only the effect that the driver feels, it's not what the vehicle is actually doing - and that fact is what actually matters in reality, if you call it what it is, a skid, a loss of control, then it becomes a better tool to use as you want to avoid these scenarios not accept it happens like there is nothing you can do about it. You can't actually do anything about under steer, over steer and you ideally want neutral steer as it's design issues, but you can do something about skidding. Skidding is the same whether travelling or not, it's external to the vehicle, skidding is essentially excess, uncontrolled yaw as you say, where you want controlled yaw to best get around a corner. Look at how a tyre works, as I know you know that, and when turning you get slip on the tyre, the slip angle is a determined by speed and desired angle of travel, once the slip angle is exceeded ie the tyre can no longer atain traction at the required angle it looses traction, it no longer actually steers so it cannot be, by definition under steer or over steer, it has to be factually a skid as that is a loss of traction, whether intentional or not (technically a wheel spin is also skidding). Consider what actually is over steer and under steer, A Nissan Navara D40 is actually a good example as it is available here and in AU, take the time to have a good look at how the steeering works, you'll see one wheel really goes over the ark if travel when on full lock, the outer wheel turns tighter than it should. What would you call this? What effect does it actually have on the vehicle? then think about it. You'll find it either over steers or under steers! At this point you will understand why calling a skid as oversteer or under steer is wholy wrong and hopefully stop doing it. The point in your work is to get facts over and improve people's driving and design etc... You generally try to explain things in defined terms, work out why something happends and explain it and if it's not what people thing, give the correct info about it. That I like about your work.

@DougAskin 3 ай бұрын

I think A or C would work, the other might work like an LSD

@Malc664 3 ай бұрын

Build the track at position C. And the two wheel drive may have an LSD or similar.

@That_Guy_Outside 3 ай бұрын

A - that would put the driver and passenger side of the car lifting and settling at the same time.

@glenwillson5073 3 ай бұрын

C - less difference between L & R front wheels.

@jayc76chai9 3 ай бұрын

C- the axle twist effect are lesser.

@jerryfrench2981 3 ай бұрын

This is why I'm not a brilliant 4 wheel driver.. I cant see much advantage on any position. I'll go C. Perhaps it will stop the vehicle crabbing sideways.