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Ripsaw XL

Ripsaw XL

Model of a high-performance tracked vehicle. Features complex suspension system and a cannon.

Datasheet:

Completion date: 19/07/2014
Power: electric (RC unit)
Dimensions: length 70 studs / width 33 studs / height 22 studs
Weight: 3.15 kg
Suspension: pendular bogies on trailing arms with shock absorbers
Propulsion: 4 x RC motor geared 3:1 from slower output
Motors: 4 x RC motor, 1 x PF M motor

With custom-built, heavy-duty tracks tested in my Grassgrinder, and four RC motors available, the next logical step was to build a Ripsaw. I have already built a small one a few months ago, but this time I wanted to make a serious model.

The model was equipped with two 150-studs long tracks, including 900 2L beams total. This means that the weight of tracks alone was close to 1 kg. Suspension system was made as close to the real one as possible, with pendular bogies housing four small road wheels each, suspended on trailing arms with shock absorbers. The resulting suspension was hard, but worked well. It seemed to transfer more vibrations to the hull than was the case with the Grassgrinder, perhaps because of the smaller road wheels and shorter bogies. The real Ripsaw comes with track pre-tensioners in the front sprockets – here, I have mounted the front sprockets on beams that were slightly bent downwards. This was simpler and stronger solution that using shocks absorbers, and it was able to reduce play in the tracks effectively, but to a limited degree.

The propulsion system was the same, with the same gear ratio, just more motors. The front RC unit controlled the steering, engaging four PF switches with its steering output. The rear RC unit controlled a PF M motor with its auxiliary output, which allowed to include one extra function: a cannon popping up from the upper hull.

The performance proved problematic, once again proving that RC motors are simply not fit for vehicles this heavy. I have put brand new Energizer batteries in the model, and all was good and well for about 10 minutes, then the performance started deteriorating quickly. The hot weather was additional issue, as both RC motors and RC units are known to generate plenty of heat, and it didn’t help that their black cases were exposed to strong sunlight. Every now and then one of the RC units would simply shut down from the heat, and I had to let it cool. This raises questions as to whether it’s possible to include a cooling system in such a model, perhaps in form of a ducted fan.

In the end, the performance was pretty satisfactory, but for a shorter period of time. The suspension worked nicely, although it was perhaps a little too hard – then again, a softer suspension would create plenty of play in the tracks. The propulsion system generated much more torque that in the Grassgrinder – it was possible to make zero-degree turns, even in short grass. The conclusion is that the design was correct, but it was crippled by characteristics of the RC equipment, such as the sensitivity to heat and enormous power consumption under strain.

Photos:

1.jpg 2.jpg dsc00206.jpg dsc00208.jpg dsc00215.jpg dsc00219.jpg dsc00222.jpg dsc00224.jpg

Video:

YouTube Preview Image

Media coverage:

The LEGO Car Blog

Categories: Misc. Tags: , , ,
  1. Sariel
    October 16th, 2014 at 18:49 | #1

    @Slung
    The video shows that precisely.

  2. Slung
    October 16th, 2014 at 18:24 | #2

    How worn out are these track pieces after you used them? Scratches from the pavement or anything?

  3. EpicMOC
    October 5th, 2014 at 19:24 | #3

    Wow! 1kg for the tracks ALONE?
    I’ve built a whole high-performance car using Mindstorms EV3 (the brick is very heavy) with Ackermann steering geometry weighing only 740g.

    Although there was no suspension…

  4. Sariel
    September 16th, 2014 at 09:13 | #4

    @kevinoufr
    It’s not for sale.

  5. kevinoufr
    September 16th, 2014 at 02:20 | #5

    hello I’m french and I would like to know the total price? and if it Was possible to have room to reproduce detail, thank you?

  6. Ev3fan
    September 9th, 2014 at 21:33 | #6

    Sees, that’s right. I’ll do that, I think.

  7. Sariel
    September 9th, 2014 at 20:41 | #7

    @EV3fan
    Or you can just join a community site like Eurobricks and share your thoughts, ideas and questions with others. It may be much more enjoyable.

  8. EV3fan
    September 9th, 2014 at 16:44 | #8

    @Sariel
    Ok, I’ve got a solution. I WON’T let me forbid to say what I think but I will proof what I’m about to say and I will write a warning in front of every comment that contains more than “oh this model is so cool” which says that it may contain something silly and that you don’t have to read it.

  9. Sariel
    September 9th, 2014 at 11:27 | #9

    @EV3fan
    Yeah, again.

  10. EV3fan
    September 9th, 2014 at 11:04 | #10

    Oh. Sorrry. Didn’t know that.

  11. Sariel
    September 8th, 2014 at 11:38 | #11

    @EV3fan
    Everybody knows this idea and you’re like the millionth person to bring this up. Let me sum it up for the millionth time:
    – weaker
    – much more expensive
    – prone to wear down really fast
    – the grip of the plastic tracks is already quite good

    Mahj’s idea is great for lightweight vehicles, and mainly for indoor driving. So, what I think is: stop commenting. Really.

  12. EV3fan
    September 8th, 2014 at 10:16 | #12

    Hey Sariel,
    I’ve found a good custom tracks solution by a pro builder , mahj, on youtube:Trachs out of lego rubber pieces.(It’s this one: http://www.bricklink.com/catalogItem.asp?P=45590)
    Here’s the vid:https://www.youtube.com/watch?v=dmR-Y4fp404&list=UU-G_RyVIfGPA7i2aKroleXg#t=36
    Now, what do you think. I think the idea is great.

  13. Ronald
    September 5th, 2014 at 21:31 | #13

    LegoMaster, that thing is so cool!!!
    I have been checking your creations the last year and you keep surprising me. You should have seen my reaction when I realized the tracks are made of a million 2L beams haha Lego must be paying you a lot to not make instructions for everybody (joke, or not?).
    I know you want to teach us how to fish instead of just giving the fish (I got your book) but I am suffering when I see your creations. I probably got every part or just buy it but a masterpiece instruction from you would be so fantastic, like one of your supercars (Zonda) or that 2K tank. First let a lot of people pay in advance for the instruction and win win. I know you don’t make full instruction but I can’t resist begging for it… please??? Best argument: “Come on… come on…”
    Btw, my cats like your hamster!

  14. Sariel
    September 3rd, 2014 at 09:07 | #14

    @TShera
    Depends on the wheels, but from my experiences with L motors, I would expect you’ll need to gear it down at least 3:1.

  15. TShera
    September 3rd, 2014 at 01:50 | #15

    @Sariel

    What gears would be best for high speed, inside that portal axle part, if propelling with an XL motor per axle?

  16. Sariel
    September 2nd, 2014 at 22:24 | #16

    @TShera
    I guess you could try… or you could buy the four pieces you need, whose prices start under $1 per piece: http://www.bricklink.com/search.asp?itemID=102719&colorID=86

  17. TShera
    September 2nd, 2014 at 21:02 | #17

    @Sariel

    Is there any way I could do it using common pieces only? I own 24008, 24009, and 9395.

  18. Sariel
    August 26th, 2014 at 23:03 | #18

    @TShera
    Well, the easiest way would be to replace the standard wheel hubs with the portal ones from the 8110 set.

  19. TShera
    August 26th, 2014 at 22:04 | #19

    Sariel,

    How could I add portal axles to an RC 42029 set? I want more ground clearance.

    Thanks.

  20. Sariel
    August 25th, 2014 at 09:26 | #20

    @Grant
    Um, I make the rear axle just as wide?

  21. Grant
    August 25th, 2014 at 04:01 | #21

    How do you get wheel’s on a car the same distance apart in the front and back? The front axle tends to be wider on my cars due to the steering system.

  22. Sariel
    August 24th, 2014 at 09:00 | #22

    @elton
    Thank you, but I think I’ll pass.

  23. elton
    August 23rd, 2014 at 19:22 | #23

    hey sariel I like your model very much and anyways could you please give me your home address cause I would like to meet you in Poland and anyway I am a am a great fan of u and it would be my honor to meet you thanks.

  24. Sariel
  25. Kaszi
    August 19th, 2014 at 10:19 | #25

    @Sariel
    I have never heard about it before. I wasn’t able to find the technic 2×1 beam. What is its name on Bricklink?
    Thanks.

  26. Sariel
    August 17th, 2014 at 11:25 | #26

    @Kaszi
    Are you aware of the Bricklink?

  27. Kaszi
    August 17th, 2014 at 11:01 | #27

    On lego.com the 2m beam costs $0,40, so the two tracks cost $720,00. Can i buy it cheaper somewhere?
    Is this modell available in your book?

  28. Sariel
    August 8th, 2014 at 23:31 | #28

    @Iaz
    I’m sure both have been done before. I’ll pass.

  29. Iaz
    August 8th, 2014 at 14:53 | #29

    Hi, I don’t know how to reach you so I thought this maybe the best way.
    Sorry but this has nothing to do with this, but I am wondering if maybe you could
    Make something different like a lego Swiss Army knife or a lego computer?

    Just a thought ☻ thanks.

  30. reznov71
    August 8th, 2014 at 12:41 | #30

    General Joe Colton’s Ripsaw?

  31. Placticine
    August 6th, 2014 at 14:57 | #31

    @Sariel
    You could always try Ultrafire/Trustfire batteries which run at about 4V per battery. These would be great for heavier models, although they may just burn out the motors. Either way, they could be a great improvement to an already amazing model!

  32. Jumper
    July 29th, 2014 at 16:22 | #32

    Nice!
    Please build the Ghe-o-rescue!!

  33. Sariel
    July 29th, 2014 at 09:07 | #33

    @Tobias Stanisfugl
    There’s not much to tell. Two RC motors for each track, geared down 3:1.

  34. Tobias Stanisfugl
    July 28th, 2014 at 23:54 | #34

    Hi Sariel
    What a huge warship! Since the Grassgrinder’s suspension layout was no issue for an sprocket free drive, with Ripsaw’s topology a really soft and long excursion one poses the question of adhesion then. So I see a bit of a dicrepancy from concept; of course, the chain tensioning mechanism is a major topic designing an high performance cross country tracked vehicle.

    Can you tell or show little more of the drive train in detail?

    Greets, Tobisas Stanisfugl

  35. Mikko
    July 24th, 2014 at 16:09 | #35

    If you are willing to pay for separate postage fees, you can order the charger from their international warehouse (the batteries must be ordered from europe, or the postage fees will be ridiculous). You can also use a NiMh charger if it’s charging voltage can be set at 1.9 volts, though most don’t have this option. Of course you can also try your luck on ebay or local shops, but I bet the prices will be much higher.

  36. Sariel
    July 24th, 2014 at 00:15 | #36

    @Mikko
    Yeah, but I don’t have a suitable charger either.

  37. Mikko
    July 23rd, 2014 at 19:02 | #37

    Sariel, if you are interested in higher voltage, maybe you should try 1.6 volt NiZn-batteries. They are really cheap on hobbyking, little over 1€ for 1500mAh AA cell. I haven’t tried them myself yet, because I don’t have a suitable charger for them (a standard charger for 1.2 volt NiCd/NiMh cells obviously won’t do), and hobbyking doesn’t have them in their eu-warehouse at the moment.

  38. Reinhard
    July 21st, 2014 at 20:29 | #38

    Cool! Its so much like mk1, yet so much better, well done, I really love it, it looks so great! Keep up the awesome work! ;)

  39. Pedro
    July 21st, 2014 at 17:58 | #39

    Thx for the link :)

  40. Sariel
    July 21st, 2014 at 17:17 | #40

    @Yeti
    Thanks, but I’m not comfortable as a judge of other people :)

    @Pedro
    Here: http://www.bricklink.com/catalogItem.asp?P=57523

  41. Pedro
    July 21st, 2014 at 14:27 | #41

    @Sariel
    OK :p can’t find it on brickstore, thats something I could use for a A-10 thunderbolt (thats one of my projects)
    I thought of a rim you modded :)

  42. Yeti
    July 21st, 2014 at 14:17 | #42

    You inspired me to make my own technic vehicle i took the 1/10 scale ferrari f1 car and made a 1960’s f1 car is there any way i could send you some pics of it for criticism? If not thats ok. Keep doing what you enjoy.

  43. Sariel
    July 21st, 2014 at 14:07 | #43

    @Pedro
    Of course it’s a LEGO part.

  44. Pedro
    July 21st, 2014 at 13:56 | #44

    hi, nice work and cool video to go with.
    just wondering if the 6 barrels canon is a lego part or a DIY part you made.

  45. July 21st, 2014 at 02:08 | #45

    Nice song pick!

    I hope you decide to build more anti-pet stuff on the chassis. Very neat to see.

    LEGO should release an official ‘super battery’ just for your creations. …That and sponsor some of your batteries and bricks. Your work is solid!

  46. Sariel
    July 20th, 2014 at 20:20 | #46

    @Joexer
    No problem, thanks for advice. I’m using really nice Eneloop batteries normally, but I wanted 9V here, not 7.4V.

  47. Joexer
    July 20th, 2014 at 19:56 | #47

    Nice work, those treads look great. Water cooling (per your design from your first book) has been more effective for me and my friends out here in California. One of our guys just took out the temp. control circuit altogether. It gets to 110°F (44°C) out here regularly, but its dry. I use a PC fan as going all Lego is extremely hard. Pc fan lowers ambient temps by 5°(2.4°C). And pneumatic(IV) tubes with water wrapped arround gives a solid 15°F (~9°C) But whatever floats your boat (when you are not in a major drought). By the way, if you don’t mind using non proprietary Lego stuff, I suggest batteries meant for rc cars, IE Hobbyking.eu, Typical Alkaline AA’s provide the standard 2500mAh but you can get a 2500mah battery with better amp draw, rechargeable, efficiency and burst/constant drain performance for like $8 usd (5.92 Euros) mine has lasted 4 years and I got a solid 3 hrs plus constantly from my(disassembled) nxt based crawler. Just a few ideas. Hope I can help a little :). Also sorry for the text wall.

  48. Lamboguy59
    July 20th, 2014 at 17:17 | #48

    Love the cannon.

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