bonox

that trailer is ingenious but actually very simple. You only need one servo - the rest are just for power. There is no programming either - he's cunningly used the servo control mechanism of the rechargable battery box. THe trailer is a great example of mechanical multiple steering radii setup, but won't help for crab variation or electric control. ( for reference, so says the creator at post #38 of that thead) many multiple axle vehicles have one or more non steering axles for simplicity when the scrub is minimal. For the trailer, the non-steered axis is mostly at the centre of rotation of the whole assembly.

bricklink is a collection of individual stores, much like ebay. If you put lists of parts into a wanted list, you can buy and remove those items from the wanted list to keep track of what you still need. For a big project, it's unlikely one store will have everything you need or if they do, there may well be other cheaper options. Search the forum for threads on how to use bricklink. The bricklink site itself also has a fairly helpful info/help section on how to use it. It's a bit clunky to begin with for new users, but I would suggest you deal with someone local with decent feedback for your first outing. also, it's good to be aware of mold variations. Sometimes you find a parts list that contains old versions of a part that are expensive. There may be a newer variant that is much more common, but it won't show up automatically from your wanted list inside a store. If you're having trouble finding certain parts that the catalogue tells you should be fairly common, this is when I go looking for alternatives.

copy the xml bit (the parts with tags like <INVENTORY> around it into the UPLOAD part of your wanted list in bricklink. Unless you want to edit <ITEM> into <ITEM><WANTEDLISTID>xxxx</WANTEDLISTID> by search/replace-all, then everything will go into your MAIN wanted list. The BL link is http://www.bricklink.com/wantedXML.asp

THe factory piece will be the most accurate, however it will depend on whether you want to put an axle through it or you want the part to capture a 3/4 pin. If the former, remake an existing piece. If the latter and you don't have a mill to create the spot face to accept the pin collar then you may be better making by printer. I think technically the simplest is to take a 5L thin and knock two holes off it. There are more colour choices in the 6632 though, so create, remake or manufacture from scratch will depend on what you want.

I disagree with that. ( ) The point here is where you put a universal joint in a drivetrain. I believe there is an implication of a certain change in motor speed by the time you get from the motor to the output (a wheel for example). You are correct in your assessment for equal torque. ie a smaller offset requires a larger force for the same moment sum. Where you're going wrong is in the torque multiplication of gearing in exchanging torque for speed (or vice versa) depending on whether you're gearing up or down. If your output shaft speed is lower than the input speed, for the same input/output power, both the torque and shaft speed change in proportion. In this case, the argument is putting the uni joint at the point of lowest torque (and consequently maximum shaft speed).

Thanks Jaap. Just bought both instructions and a shoot tin of new parts

rebrickable.com has many MOC's. If you notice the banner across each, it will tell you if instructions are charged or free ($$$ or MOC), a link to the homepage or where to buy instructions and what form those instructions take. Some are full TLG type, others PDFs from CAD models, other might just be a CAD model or sequence of photos. mocplans.com is another

if you gear up then down by the same amount, then torque on the joints outside the intermediate shaft won't change (neglecting losses). Only the torque in the intermediate shaft will change. You are correct in a nett zero analysis. Regarding Erik's comments about stages, i've not done any analysis on it, but it's possible that due to the radial loads you get from gears, that the friction in the 'bearings' could sum to different values based on differing magnitudes of change at each gear pair. Would be interesting to investigate. In general though, I believe tribological studies show that for equal power transmission, higher speed equals more friction even though the coefficient vs speed curves tend to taper off with increasing speed.

thanks gents - part order already placed :)

While we're here though, what wheels and tyres have you used for the trailer please?

Brilliant. You'll have another buyer as soon as you finish the parts list for the trailer :)

welcome. Does your irresponsibility extend to owning a 2 wheeled honda?

nice combo of studded, studless and system :) Any problems with the universal joint between the rear axles binding with the suspension movement? It looks like a similar issue motorcycle swingarms have with changing geometry length (ie distance between arms on the triangle change length as the axle to axle suspension angles change).

it's got seven positions using the train remote and quite a few more options if you use an sbrick instead.

Correct. Steering arm length is what I called offsetting the rack from the wheel pivot axis. It's not so much total weight as weight per (steering) axle, plus the friction of the tyre on the ground plus friction in the steering assembly and axle/gear runs that will determine whether your chosen motor will be capable. If you had a continuous motor, you can gear down a lot - like gerger did with his Grove 6400 - but with the servo you're more limited, so you need relatively light steering or accept the smaller stering angle that will come from gearing it down a bit. You could find that your design will work on a hard floor but not carpet for example.

i think you're talking about rack and pinion. Either way, you'll find it about impossible to have multiple servo motors linked at different rates to different axles. Most sove this mechanically with different gear ratio's and or mechanical offsets of the steering rack from the wheel pivots on each axle to keep the steering arcs at suitable radii with respect to the other axles. ie one steering shaft controlled by your servo, with axle steering angles controlled by gearing or offsets. As for 'can the servo handle it', you're down to tyres, surface, vehicle weight etc - too much to estimate with no further data. edit: speeling for factory examples, look at the 8454, 8053, 8421 etc

I'm pretty sure all the printed bricks are real. I know some of the stickers are too, but there are a few like "December" I don't know of. We've got lots of charity events around here like the Variety Club Bash that paint up their vehicles just like that! example:

This bloke (http://www.google.com.au/url?url=http://www.hackvandedam.nl/blog/%3Fpage_id%3D559&rct=j&frm=1&q=&esrc=s&sa=U&ved=0CBQQFjAAahUKEwi57amm-bPHAhVJoZQKHaxvBg8&usg=AFQjCNGFgrGwJgnsWkR6Yfn7mbJ3rXVReA) says that the PWM frequency is 1150Hz. That's quite audible for people and sounds like a 'high' pitch, but nothing like a top C from a soprano or cornet. The noise is the motor being driven intermittently (rapid start-stop) at that frequency. TLG have done it that way because it's cheap. You can drive motors at almost any frequency you like, but you need a driver circuit with a frequency above human hearing before it will appear to be 'silent'. It isn't actually silent of course, just inaudible. As an interesting aside, changing the drive frequency is commonly used to "play tunes" on motors. I believe there's someone who has used an SBrick and a PF motor to play the starwars imperial march.

Once you get a handle on the different categories of parts - Bricks, plates and tiles for example have a modified variant that isn't always obvious, learning the difference between old technic bricks and new technic liftarms etc - finding things in the catalogue gets much easier. Another good resource is putting up a picture of an off part in the thread for that purpose (http://www.eurobricks.com/forum/index.php?showtopic=67887) and hoping an inmate here can point you in the right direction. Something to note that that you may have some parts in that collection of yours that are not lego and will consequently not exist in the lego parts catalogues.

That's a very good point and probably why most people have at least one 'dark age'. It may not necessarily be a lack of interest, but perhaps a higher priority of other things that leads to one being neglected. I used to have an old land rover that I loved and spent large quantities of time and money on. However with changes in legislation, dwindling parts supply and demands from a growing family, it became a better proposition to get rid of it. It didn't necessarily mean i'd lost interest at the time but with a long enough absence you no longer look forward to the idea like you used to.

That's a brilliant set and a great example of modularisation. I'm definately going to build an 88 :)

How so? This whole thread is about perpetual motion - all the way up to the thread title. It's merely another song lyric comment in regard to the quoted line about the earth being a perpetual motion machine because of rain cycles, when it's clearly not! You didn't have a problem with the first lyric - what's wrong with the second? The server was even kind enough to alter the original lyric into a lego theme too The fastest and quickest way to start showing that this project has legs is to create the spinning disk just as it is - no magnets, doodads or widgets necessary - and give it a spin. Put it on video and show it stays spinning for a few weeks without needing another push and you're well on the way to showing feasibility.

torque is a twisting 'force'. The slower you make an arbitrary motor spin, the more torque you get out of it for the same input power. In practice this means that if you gear a motor down by 2 input turns to 1 output turn, you'll get twice the twisting force (torque) out of it. There are obviously some losses in there due to friction in the gearing, but the idea is what i'm trying to get across. To a first approximation, the output power of the L and XL is the same (http://www.philohome...s/motorcomp.htm - about 2W mechanical output at 9V). The L turns twice as fast as the XL and therefore has about half the torque of the XL. That means the XL is about twice as good at moving a heavy truck - but it'll do it at half the speed of the L. Taken to extremes, you can gear down a tiny motor to produce enough torque to twist a steel bar (or plastic lego axle), but it might take all day to make one revolution. This (and the life of your lego parts) is a tradeoff you're going to have to make.

Some edumacation courtesy of MC Hawking (for the upcoming hurt souls ) Creationists always try to use the second law, to disprove evolution, but their theory has a flaw. The second law is quite precise about where it applies, only in a closed system must the entropy count rise. The earth's not a closed system' it's powered by the sun, so megabluck the damn creationists, Doomsday get my gun! That, in a nutshell, is what entropy's about, you're now down with a discount.

In a few places i've seen, the arocs and volvo loader were priced significantly higher than the crane. RRP here is AU$279 for the crane and AU$369 for the loader. If they are the same price for you, i'd suggest you're getting a very good deal on one or a very bad deal on the other.