Suspension or no suspension?

[clarkdef]

Hello all, I have been developing an RC car, it is a hill climb car. Basically there is a section of hill in my area that I try to set a time on once a year around Christmas time. Last year the car was a power function car, with two large motors, it wasn't the fastest but I plan to evolve. The car had suspension, really didn't need it as it was so slow.

This year is a different story, I have some serious power, 20km plus on the flat. Testing at that speed I have come to know that no lego suspension that I have come up with can handle that speed! The tie rods fall off and on turn in the wheels cave in. The purpose of suspension is for it to be functional, but it's just acting as a very weak link.

I just finished a chassis today, I tested it and still same result, so in total ANGER I ripped it apart! So I am at the stage of dropping the suspension, seems pretty boring not to have it. though.

This may be an interesting topic, so please share your experiences and frustrations.

[Zerobricks]

Depends on the terrain I guess... Having no suspension and hitting a small bump can cause the vehicle to flip.

[andythenorth]

I have a couple of projects using PF XL motors which have no suspension between motor and wheels. It's hard to build a strong compact vehicle with both a reliable drivetrain and suspension. For steering axles, it's even harder.

Of course, there are a lot of trial truck MOCs that have done all of this successfully, but they sometimes look bulky, and heavily engineered.

The pictures attached are the rear drive for an 8x8 truck. There is walking-beam suspension between this double-drive axle unit and the chassis, but no suspension within the axle unit.

The axle unit is designed quite carefully. All gears are meshed with liftarms, and there is no way for them to slip unless they actually break. The gears are also easy to replace The unit won't twist due to traction torque, but has some flex laterally, so will twist a small amount to follow uneven ground. Diff locks are essential (inspired by Sariel).

I'm working on another 8x8 truck which is articulated. This will have no suspension at all for the axles, but will have 3 degrees of movement in the chassis. It will use Power Puller wheels which also have a lot of flex in the tyre wall. Inspired by http://www.nov.com/W...MODEL_8860.aspx

These are *not* 20km/h though

Edited August 11, 2013 by andythenorth

[clarkdef]

Depends on the terrain I guess... Having no suspension and hitting a small bump can cause the vehicle to flip.

Well exactly, you need some bump absorbing. I ordered some rubber pieces on bricklink, I have a wild idea that probably wont work! The terrain is dirt.

I have a couple of projects using PF XL motors which have no suspension between motor and wheels. It's hard to build a strong compact vehicle with both a reliable drivetrain and suspension. For steering axles, it's even harder.

Of course, there are a lot of trial truck MOCs that have done all of this successfully, but they sometimes look bulky, and heavily engineered.

The pictures attached are the rear drive for an 8x8 truck. There is walking-beam suspension between this double-drive axle unit and the chassis, but no suspension within the axle unit.

The axle unit is designed quite carefully. All gears are meshed with liftarms, and there is no way for them to slip unless they actually break. The gears are also easy to replace The unit won't twist due to traction torque, but has some flex laterally, so will twist a small amount to follow uneven ground. Diff locks are essential (inspired by Sariel).

I'm working on another 8x8 truck which is articulated. This will have no suspension at all for the axles, but will have 3 degrees of movement in the chassis. It will use Power Puller wheels which also have a lot of flex in the tyre wall. Inspired by http://www.nov.com/W...MODEL_8860.aspx

These are *not* 20km/h though

Very clever system you look to have, can't say I can see how it actually works.

I gave up on front driven wheels because like you say not easy, the uni joints kept separating in the middle with high revs. It has forced me to use trailing arm on the back not independent control arms, the driven arms being two or three buggy motors, making it an extremely heavy suspension arm! Thus making it pointless.

Your idea on chassis flex could be a good thought though.

Yes speed brings lots of new and exciting challenges. Love it though...

[MrNumbskull13]

Pendular suspension is relatively easy to build and can be made very strong! You could make a two speen gearbox aswell, 1st gear with a lot of torque for the hill climb and 2nd gear for the fast bits.

[Zerobricks]

Pendular suspension is relatively easy to build and can be made very strong! You could make a two speen gearbox aswell, 1st gear with a lot of torque for the hill climb and 2nd gear for the fast bits.

Pendular suspension doesnt cusion ANY shocks. Its useless for fast vehicles.

[Technyk32231]

Try front and rear floating axles, look at doc brown's 1932 hot rod for some good inspiration. Floating axles generally can take more punishment.

Edited August 11, 2013 by Technyk32231

[andythenorth]

If I was setting out to build a fast hill climb buggy, I would probably use:

- long rear trailing arms, one per axle, on soft springs.

- two PF XL motors - one per rear wheel, mounted inboard in the centre of the chassis, so they are sprung weight; or use the buggy motor

- a gear train of 12 and 20 tooth gears along each trailing arm. The friction of these will suck up power, but they will be robust.

- front suspension: I would use a live axle sprung on trailing arms

- one PF XL motor, or the buggy motor

- no diff (assume the ground is rough and the wheels can slip = no diff needed, also hill climbing mostly straight?)

- use these steering components http://www.bricklink...tem.asp?P=11949

- use double steering links on each side to reduce the chance of popping them off when hitting bumps.

This is conjecture, I've never tried to make anything that goes quick

Edited August 11, 2013 by andythenorth

[z3_2drive]

Does it have to have high clearance? Can it be RWD? If not I can show you some pictures in a day or two of a pretty nice front suspension I used on a car built for speed, and it could handle bumps and jumps no problem, only the bottom got scraped a bit by the asphalt, which wont be an issue on dirt/you could add a skid-plate. It also has caster so steering is better. Edit: for the rear, whether you use suspension or not, try to do direct drive. Even a single pair of gears will drastically reduce power, or at least perpendicular bevel gears.

Edited August 11, 2013 by z3_2drive

[clarkdef]

Pendular suspension is relatively easy to build and can be made very strong! You could make a two speen gearbox aswell, 1st gear with a lot of torque for the hill climb and 2nd gear for the fast bits.

I have messed around with gear boxes. they work awesomely! But in the end I think they absorb power as they heat up also you have to avoid many cog types to avoid breakages. I use direct drive mainly... I know it's boring haha.

Pendular suspension doesnt cusion ANY shocks. Its useless for fast vehicles.

Yes very true.

Try front and rear floating axles, look at doc brown's 1932 hot rod for some good inspiration. Floating axles generally can take more punishment.

Thanks. I like the way "The Tudors" front steering system looks!

If I was setting out to build a fast hill climb buggy, I would probably use: - long rear trailing arms, one per axle, on soft springs. - two PF XL motors - one per rear wheel, mounted inboard in the centre of the chassis, so they are sprung weight; or use the buggy motor - a gear train of 12 and 20 tooth gears along each trailing arm. The friction of these will suck up power, but they will be robust. - front suspension: I would use a live axle sprung on trailing arms - one PF XL motor, or the buggy motor - no diff (assume the ground is rough and the wheels can slip = no diff needed, also hill climbing mostly straight?) - use these steering components http://www.bricklink...tem.asp?P=11949 - use double steering links on each side to reduce the chance of popping them off when hitting bumps. This is conjecture, I've never tried to make anything that goes quick

4 to 6 buggy motors direct drive is what I am aiming to use, it is very solid trailing arm on the units. The front is my real issue those hubs look the money to me, will have to get that F1 car!

Does it have to have high clearance? Can it be RWD? If not I can show you some pictures in a day or two of a pretty nice front suspension I used on a car built for speed, and it could handle bumps and jumps no problem, only the bottom got scraped a bit by the asphalt, which wont be an issue on dirt/you could add a skid-plate. It also has caster so steering is better. Edit: for the rear, whether you use suspension or not, try to do direct drive. Even a single pair of gears will drastically reduce power, or at least perpendicular bevel gears.

Doesn't have to be high clearance, maybe 2-3cm. Yes strictly rear wheel driven! Uni joints don't survive in the front... I would love to see your idea. And yes gear I avoid.

[z3_2drive]

4-6 buggy motors? sounds beastly My idea uses the new hubs though, which I got from Lego Direct. Since I took it apart I will have to rebuild it or find pics.

[clarkdef]

4-6 buggy motors? sounds beastly My idea uses the new hubs though, which I got from Lego Direct. Since I took it apart I will have to rebuild it or find pics.

I should probably just use four, six makes the car too big, a few of them need replacing because I stored them in an air tight case for years... and now they are rusted and make a lot of noise. I do want those new hubs, if merely to play with ideas.

[andythenorth]

Get the hubs on Bricklink? Buying the F1 car is an expensive way to get them (It is a good set though).

[z3_2drive]

Just built this, hope it helps:

Enjoy! And yeah those hubs are pretty good aside from the slight wobble.

[andythenorth]

Apart from it looks good (it does) - what advantage do you get from moving the shocks inboard?

You could just mount them to the bottom arm-with-towball...?

[z3_2drive]

Apart from it looks good (it does) - what advantage do you get from moving the shocks inboard?

You could just mount them to the bottom arm-with-towball...?

because there is no efficient way to mount them that way without the shocks bending, there are too many offsets, and this gives a softer and slightly more travel suspension movement

[clarkdef]

Get the hubs on Bricklink? Buying the F1 car is an expensive way to get them (It is a good set though).

Yes but after you work in the postage all the way to NZ, you might as well of just bought the car! But still good point.

Just built this, hope it helps:

Enjoy! And yeah those hubs are pretty good aside from the slight wobble.

Looks great man, and wow I appreciate the effort you went to making this, looks like you have a touch of castor applied, which helps strength a lot. Though you have to put it through a grueling test to see if it works lol. I will post a video of the monstrosity I made, and show you my testing process.

Yours is better than the one I just made in a few obvious ways. It is smaller, it has more travel so I could rest it at halfway and the steering system looks easier to fit to the buggy unit.

Though other than the hubs (I use the ones of 8880 supercar) it looks the same as systems I have made before, I usually setup the castor by tilting the subframe.

Edited August 12, 2013 by Blakbird
: Removed large number of quoted images.

[z3_2drive]

No problem, I might use it soon anyway on a large RC car, and do you have a lego.com account so you can buy from lego direct?

[clarkdef]

No problem, I might use it soon anyway on a large RC car, and do you have a lego.com account so you can buy from lego direct?

No I would say the postage would be too much. Will check it out though, is it lego.com?

[clarkdef]

A rough overview of what I came up with the other night. http://www.youtube.com/watch?v=SHekv7CfUYs&feature=c4-overview&list=UUmGNbWRBJsu1XieU3aJ2zyQ

Would like to try z3s setup once I get them hubs.

[Doc_Brown]

Hey that looks good! Can't wait to see the rest of the buggy!

Here's what I'm working on atm, pretty strong, and smashed it like you did in your video, and didn't break! haha

I only have 2 RC motors tho, but building a 2 speed sandwiched in-between the motors.

Waiting for bigger wheels too.

Those hubs do have a lot of play tho. Prob not the best for high speed driving.

[clarkdef]

Hey that looks good! Can't wait to see the rest of the buggy!

Here's what I'm working on atm, pretty strong, and smashed it like you did in your video, and didn't break! haha

I only have 2 RC motors tho, but building a 2 speed sandwiched in-between the motors.

Waiting for bigger wheels too.

Those hubs do have a lot of play tho. Prob not the best for high speed driving.

That has a good width for stability, it does look strong. It'd probably beat mine around the corners. The hubs to me look the same as the crawler hubs (cut of the excess and it is essential the same). So the play should be the same? When you plug in an axle, you rid a lot of play.

Haha also it's the ultimate test to see if it separates from the tie rods!

[Doc_Brown]

haha yeh sure is!

Well im not sure if it would beat yours, my buggy is pretty slow. lol and turning radius isn't the best.

I put an axle in them and it doesn't do much. I have an idea to make a thin washer and see it that helps.

After testing it the steering needs a bit of work, not quite return to center if you know what i mean.

Hopefully my bigger 81mm wheels will arrive tmr.

[z3_2drive]

Here's my car, just to see how the steering is incorporated, along with some fun testing

^rear axle is direct drive with no diff. While it may reduce cornering (unless it starts to drift ) it helps keep stable at top speed and there is minimum power loss.

^when suspension is compressed (such as when hitting a bump at high speed or going over rough terrain) there is some toe-in, which is perfect because it will keep the car straight and it wont lose control

I may make a video today or tomorrow if I have time.

EDIT: I tested inside because I knew I'd crash eventually with the poor IR signal And I did, but a near full speed crash will make anything with lego fall apart, in this case the front axle assembly separated from the rest of the chassis. As for steering-everything is perfect except the steering rack came out so one tie-rod separated from the rack but not the hub, but trust me, at top speed, along with some small jumps, this holds together perfectly during a crash I actually think sections coming apart is better, since it absorbs the impact instead of the pieces at the very front taking all the force and possibly breaking.I like the setup in your video a lot, it could be used for a large scale stadium buggy or baja truck.

Edited August 13, 2013 by z3_2drive

[MrNumbskull13]

Put a bumper on the front! :D