johanby

Eurobricks Vassals
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Posts posted by johanby

  2. Posted

    Yeah peeron has been very flaky for the last couple of days.

    You can download a full good quality PDF here:

    http://www.worldbricks.com/lego/lego-instructions/by-number/7700-7799/7777-trains-idea-book.html

    Sorry for going slightly off-topic: I have managed to find PDF files of most of the old idea books, but have so far failed with finding "Das grosse Lego buch" nr 239. http://brickfetish.com/ideas/239/239_1968.html

    Has anyone seen it scanned somewhere on the web and feel like sharing this information?

  3. Posted

    I always thought that there was some kind of PWM system to regulate the power delivered to the motor, from the 8878 battery or the ir-receiver. Hence there is no (resistive) power dissipation that needs to be cooled off. But I actually have no idea how this is implemented or if this is the case.

  4. Posted

    So, a new motor, borrowed battery box and IR receiver from the 7939 and my 7740 ex-12v loco is now motoring round my old blue track under PWM speed control...lovely.

    I have tried the same, but find that the new wheels with technic axle connection (e.g. http://www.bricklink.com/catalogItem.asp?P=55423 ) have trouble staying on the blue track, especially on switch points. I wish there were similar wheels like http://www.bricklink.com/catalogItem.asp?P=wheel2a but with technic cross axle connection instead.

    Then I got to thinking...I have twenty original LEGO locos spanning 1968 to 1985 all motorised with the old 4.5v classic 4x12x3 1/3 4.5v motor units.

    The 7722 train set used the 4.5v motor and a 4.5v battery tender, but one of the pages in the instructions shows how a later 9v motor can be adapted to replace the 4.5v unit. Figuring that the 4.5v motor was the de facto standard for 30 years, I concluded that exactly the same adaptation would work for any train using the old motor.

    http://www.peeron.com/scans/7722-1/30 for the scan

    Actually, the adapted motor you refer to as a 9V motor is the newer 12V type motor http://www.bricklink.com/catalogItem.asp?P=bb12v . However, this does not change any of your conclusions. I really like what you have done and will try it myself.

  5. Posted

    It's worth mentioning they only provide a momentary output rather than a constant. Obviously meant for a gear change function or something similar....

    I am not so sure I will call it a momentary output. It works fine and deliver a constant output, as long as the load is not too heavy. I.e., if I stall the motor connected to the auxiliary output, the unit seems to cut the current at some limit. Thus the output seems current-limited compared to the regular output. For instance, if I connect the two 5292 motors to the auxiliary output, they will run freely as long as the car is not on the ground (no load), but as soon as it is put on the ground, the car will almost not move at all. However, I agree that the conclusion must be that the auxiliary output should be used to simpler tasks like gear shifting.

  7. Posted · Edited by johanby

    Two of the remote controlled racers (8475 and 8366) from 2002/2003 have a control unit called "RC Receiver Unit with Auxiliary Output (6272)", see http://www.bricklink.com/catalogItem.asp?P=6272c01 or http://www.peeron.com/inv/parts/6272. The control unit has a red connector which is connected to two RC race buggy motors 5292 (in parallel), but also one extra grey colored output (I guess that is the auxillary output). I can control the red output with the remote control, but nothing happens when I connect the grey output. Does anyone know how to control this output?

  8. Posted

    Hi there,

    It is possible to use an adapter that is male-male or female-female depending on what you need. If you have the parts you can make a cable quickly, you only need to wire 3 pins. TX-RX RX-TX and GND-GND. Or you could make this as an adaptor and just use it with a straight through cable.

    When i bought mine secondhand mine too came with the mac stuff, so i just modified that cable.

    Mike

    Yep. I cut away the macintosh connector and soldered a female serial connector to the wires according to your instructions. Will try the interface this evening to try to get som life in it (at least the on-connector works). Thanks for all help!

  9. Posted

    At first i thought i had a broken unit as i bought mine secondhand in unknown condition without a power or serial cable. The 10VAC power pack from the 9V train regulator was suitable but it took me ages to realize the serial cable wasnt a simple straight through type, it is actually more like a null modem cable, where RX goes to TX and vise versa. After that the fun began of writing some programs.

    I too got my unit second hand, however with a macintosh cable which is totally useless for me. Therefore it is very valuable to hear that the serial cable should be of null modem type. My problem is though that all null modem cables I have found so far have female connectors in both ends (in order to connect two computers). Since the interface also has a female connector, I guess the null modem cable needs to have one male and one female connector. Is it possible to find such null modem cables or does one have to solder it by oneself?

    Another questio: Did anyone try this software (Flowol http://www.flowol.com/InterfaceLEGOB.aspx) for interface B?

  10. Posted

    Hi, I guess you confused Radius with Diameter. the inner diameter of a standard 9V circle is 72 studs. The outder diameter is 88 studs. Thus the Radius at the track center is 40 studs.

    fW

    Yes, that sounds correct. One (straight, but I guess also the center of a curved) rail piece is 16 studs. A full circle consists of 16 pieces, i.e. 256 studs. Thus the diameter of the center would be about 256/pi =81.5 studs.

  11. Posted · Edited by johanby

    Peeron.com lists the 8887 "Transformer 10V DC" also as 86444, "Electric Train Speed Regulator 10V Power Adaptor for 120v 60Hz". Bricklink.com has various "Transformers" listed, so for European use, the 10VDC 9833 "AC Adapter, 230V - 10V Transformer" should work. Note that there is a 9833-3 "AC Adapter, 230V - 10V Transformer Type G Plug (British)". See http://www.bricklink.com/catalogList.asp?q=transformer for the entire list. Peeron lists the 9833-1 as 230V, and 9833-2 as 120V (see http://peeron.com/cgi-bin/invcgis/psearch?...&limit=none ).

    I think the 9833 Adapter is an AC adapter and thus not suitable for the 8878 battery. See http://cache.lego.com/downloads/Education/...e2010School.pdf page 27.

    By the way, I use a 12V/500mA generic adapter (positive center) with good results for the 8878. This is however something you do at your own risk if you want to try...

  13. Posted

    So I guess the only way to change the stiffness of a spring is to change its length. A non-destructive way would be to make combinations of springs in series or/and in parallel. Two springs with stiffnesses k1 and k2 would then have an effective stiffness k1+k2 in parallel and k1*k2/(k1+k2) in series. A destructive way, but with more freedom, would be to cut the spring (gives a stiffer spring) or add extra pieces (gives a less stiff spring, however care must be taken so they not overlap (sit in parallel), effectively making a stiffer spring). On the other hand, this procedure also changes the precompression...

  14. Posted

    Incidentally, there IS strain in the system as this external load is being applied, but it is a small tensile strain in the piston and cylinder which is being relieved.

    That is the key point! Thank you for a very good explanation, now this makes sense to me. Obviously, the precompression only moves us to another point on the force-displacement curve, with the slope/stiffness being the same. So it means that the constitutive equation instead would be

    F=F, for F<F0

    F-F0=kx, for F>F0

  15. Posted

    In either case we have a 500 g/cm spring, but in the second case we need to apply at least 125g of load before the spring starts moving which gives the impression of more stiffness. Another way to put it would be that the spring rate (stiffness) is a function of the spring, but the spring loading is a function of installation (free and compressed length). The modifications proposed change the installation but not the spring.

    Well, this is where I disagree. All materials (OK, most materials) are linear elastic. That means that an applied stress (i.e applied force for constant cross section) will yield a (compressive or tensile) strain (and thus elongation/compression) which is proportional to the applied stress (the so called Hooke's law). To precompress the spring will not have the effect that you need to reach some limit stress/force until a strain/compression will appear (since that would mean that the material was not linearly elastic). An applied stress/force on a pre-compressed spring will be compressed, however not as much as on the spring without precompression. This means that the spring (assembly) is effectively stiffer.

    It is easy to test by hand.

  16. Posted

    Strictly speaking the "stiffness" or spring rate of the shock is the same whether you put a bushing on it or not. The spring rate (typically denoted with a "k") is a constant for most springs and is the amount of linear (or rotational) motion per unit force. In imperial units this is typically pounds/inch or Newtons/centimeter in SI. Adding a bushing increases the preload on the spring by making it start in a more compressed state and therefore with a higher initial load. The additional force to make it compress a certain amount remains the same.

    With all that being said, this is still a great idea! It will have the effect of providing more support for heavy models. Shock absorbers for R/C cars and trucks almost all contain a similar mechanism for changing the length.

    Now if only we can find a way to make a stiff spring softer.....

    Yes and no. The total force required to fully compress the spring would be the same with or without the bushing (I guess the masses 600g, 1300g, etc, indicated in the picture above was the the corresponding force to fully compress the spring). On the other hand, the total travel distance decreases when inserting the bushing. Hence the stiffness (i.e. the ratio between applied load and compressed distance) will increase. Therefore the spring will be stiffer, but it cannot carry a higher load until fully compressed.

  18. Posted

    Taking all solid mechanics issues aside, there is of course another problem. A wheel with 30 mm diameter would need to rotate with about 14000 rpms to achieve a speed of 80 km/h. A bigger wheel would of course need less, but still a wheel with 60 mm diameter would need to rotate with 7000 rpms. The XL motor would need an upgearing of about 32:1 and the race buggy motor would need an upgearing of about 5.4:1. Heck, even the high rev low torque 2838 motor would need an upgearing of about 1.7:1.

  19. Posted

    Interesting! I suppose you use the 4.5V motor or is it the 12V motor? Are you having the battery on full voltage (7.2V) or did you choose a lower voltage? By the way, does anyone know how high voltage is it possible to use on the 4.5V motor without damaging it?

  20. Posted · Edited by johanby

    That depends. For me, the blue rail has significant nostalgic value from my childhood and I prefer using it over newer rails. On the other hand, it works best with the trains from that period and also takes more time to set up. Moreover, my Emerald Night tends to derail in the blue points, but as long as you don't use points, it works fine on the blue rail.