Tagged: 1963 Willard Indy Special, D7.5, DArt, Indy Roadsters, tires, wheels
- This topic has 28 replies, 10 voices, and was last updated 2 years ago by DB.
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March 15, 2021 at 11:15 am #18333
I thought I would let everyone know about my progress in designing, building and testing a 3D printed chassis for our Indy Roadster class. For nostalgia’s sake I’ve been working on an Eldon Indy Roadster which roughly represents the Watson Roadster of the time.
As my printer has a very small bed the chassis had to be made in two pieces and aligned with piano wire pins, this does give the advantage of a wheelbase that will adjust to most roadster bodies.
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The whole process has helped me use up any spare time that I thought I had as I had to diagnose and partially rebuild my printer ( each new part took a month to arrive and I didn’t get it all figured out the first or even the second time) and then had to start learning Fusion 360 in order to make the kinds of designs I was interested in. I can’t tell you how many iterations I printed that didn’t fit the way I was expecting before I realized that my thumb had been hitting the reset button on my digital calipers. I am getting close. Here’s the latest test fitting.
One of the greatest design challenges was getting the ff050 completely ahead of the edge of the cowling in order to comply with the spirit of a front motored build. The problem is that those tiny slim line motors are proportionately bigger than a V16 and its tough to get them into the space that originally had a 4 cylinder. Now I’m going to order axles, gears, bearings and a guide to make sure of my final measurements. In the meantime I’m going to start working on the body again.
I hope that by this fall we can have an in person debut of the Indy roadster class. I look forward to seeing all your designs.
Cheers
Steve
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March 15, 2021 at 12:27 pm #18336
Very very COOL Steve, and the ‘variable length’ would I guess make the chassis more viable for other cars/classes as well, multi functional!! :good:
Question though, and I’m sure others waaay more knowledgeable than I can opine… Do you think that your initials, the ‘open/cut out’ part of the chassis may compromise the structural integrity? Perhaps ‘etching’ them, or a raised low profile may work better? Regardless, I’m sure those here may be lining up soon, if you intend to produce/sell?
Stay well!
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March 15, 2021 at 1:28 pm #18337
Hi Drew
Thanks for the compliment. I am still developing this chassis and hope to do basic debugging on my Plastic track. The chassis as it stands is fairly stiff but the space just over my initials is designed to hold some weight, either a piece of brass or some lead in order to move the center of gravity further towards the rear axle. with brass glued in it should be extremely stiff, my initials are just a little bit of vanity and are not likely to stay as is. The needs for flexibility in certain planes of a slot car chassis is very complex in such a small narrow chassis with a front motor but I am experimenting with some webbing reinforcements in order to keep the flex only where it’s wanted. 3D printing allows me to vary the thickness of the chassis strategically and Fusion 360 even has tools to show where the stresses are, although these are still beyond me. I am trying to modify my design so that I can do a precise wheelbase for those that already have bodies that they would like to fit. The material I am using is PLA which is very stiff but somewhat brittle and I’m going to experiment with an enhanced PLA, PETG and ABS to see which is the best combination of printability and durability. If I can get my design refined enough to be useful to others I’d certainly consider producing at least a small run. I think the Indy Roadster class is a natural for this type of chassis as between this chassis and Art’s body anyone could build a car to qualify for this class.
Cheers
Steve
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March 16, 2021 at 9:32 am #18347
<p style=”text-align: left;”>Well done Steve! It takes great commitment on your part to learn the software and troubleshoot an refine your design. It looks great so far and I look forward to seeing it on the track.</p>
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April 21, 2021 at 6:58 am #18446
Good Morning Racers!
I thought I’d share an update on how the 3D printed chassis project was going. Unfortunately the adjustable chassis idea was just not workable as in order to have enough strength it meant that it would be too wide for some of the roadster bodies eligible for this class. Luckily, as my fusion 360 design skills slowly improved I found that parametric modelling allowed me to easily change the wheelbase in software for each individual car. My wife, who has been very supportive of my various hobby obsessions even bought me a full size 3D printer ( a Tronxy XY-3 Pro ) so that I could print a chassis in one piece.
I found a free file on Thingiverse for printing a Dremel chop saw attachment and with only minor modifications I had a way of making precise cuts for the motor shaft, the tubing adapter, the spring connector and the 2mm gear shaft.
I went through several iterations of the chassis design to make sure all the components would fit and align properly and that the chassis would be strong enough to take the abuse that a roll over expert like myself could inflict. Here is the final result in black and another earlier version in orange, for greater visibility, sitting on the 3D printer bed.
There’s some more work to do fitting and testing the components and then trying the whole thing out on my plastic test track. I’ll try to do another update in a couple of weeks. In the meantime you all stay healthy and we will be racing again by the end of the year.
Cheers
Steve
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April 21, 2021 at 1:37 pm #18481
Steve. Great to see what can be done with a little ingenuity!! I have been looking for something similar to your chop saw attachment ever since I discovered that square cuts were much easier to work with than my freestyle ones!! :wacko:
Would you consider making one for me?? If so let me know how much and we can work out the details.
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April 21, 2021 at 2:30 pm #18482
Stellar work on the chassis Steve!
That mini chop saw is also awesome!
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April 21, 2021 at 3:25 pm #18484
Wow, Great job.
That chassis can easily go viral on the Scratch32
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April 21, 2021 at 4:14 pm #18485
Thanks guys
At some point I think I’ll try to get a list of the wheelbases and overall chassis lengths of the bodies that people would like to use so that I can modify and archive the appropriate print files for each body. I’ll need to finish my testing of the final chassis first. There are also some hard limitations on what can be designed. The chassis at this point is exactly 20 mm wide at its widest point and can not be made any narrower without rotating the motor 90 degrees. The position of the motor in the chassis can not readily be set back without running afoul of it’s front engined intent, as it is already at the base of the windshield on my Eldon Watson Roadster, though other cars may have a little more leeway. The wheelbase which is currently 66.9 mm can be lengthened readily but using a spring coupler for the shaft means there are some real packaging constraints and the current space of about 18 mm between the motor and the support for the rear axle and gears is the only place to shorten the wheelbase. With careful fabrication the most the wheelbase could be shortened would be about 10 mm. If you wanted to use body posts for mounting the body the front post would have to be ahead of the guide and the rear post behind the crown gear. These limitations are not unique to this 3D printed chassis but are based on the provisional rules, scale and packaging constraints. There are many alternate ways to mount a body but they would have to be accounted for in the chassis design. I still have a lot to learn about 3D printing and design but I think it is another tool that can make our Hobby more rewarding.
Cheers
Steve
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April 21, 2021 at 4:29 pm #18486
Great work Steve! :good:
The Happy Canadian Scale Modeler!
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April 27, 2021 at 8:50 pm #18500
Amazing work Racer68! Opens up a new dimension for the hobby. You’re a techno wizard!
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April 28, 2021 at 3:25 pm #18507
Bracket for shaft bearing
Cheers
Steve
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April 28, 2021 at 3:30 pm #18508
I added the bracket as the shaft bearing was popping out at speed, the snap fit I had designed was enable to restrain the torque of such a mighty motor!
All better now, things are starting to slowly pull together.
Cheers
Steve
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October 14, 2021 at 2:43 am #19896
Hi Racer68,
I’ve got one of your chassis left for anyone contemplating this class – I can include it with any shipping DArt online order too – Racer68’s ask is just $20 – a great deal if you ask me…
The Happy Canadian Scale Modeler!
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April 29, 2021 at 9:34 am #18499
Hi guys
I thought I’d give a quick update on my Roadster chassis. I scavenged some parts from existing cars so that I could start some testing. Very quickly I found that the shaft bearing would need some additional support as snapping it in had allowed it to occasionally pop out at speed and I didn’t want to glue it in until the entire car was finished and ready to race. So I designed a little screw in brace. The 3D printer really has trouble printing tiny parts and holes but after a couple of iterations I came up with this :
It’s strong enough to accept the small Professor Motor body screws I had on hand and keep the bearing in place, while still being removable for any drive train changes.
Cheers
Steve
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April 29, 2021 at 11:58 am #18520
Looks like your R&D work is proceeding well!! :yahoo: Very slick!! Can’t wait to see it on track, hopefully soon.
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October 14, 2021 at 11:03 am #19897
Nice work Steve! Digging out my chassis and parts for assembly as we speak.
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October 30, 2021 at 4:25 pm #20067
Here’s some of the work that I’ve done on the body of my roadster. It has a provisional exhaust, nerf bar and roll bar. I’m trying to figure out the proper fuel filler, steering arm, wheel inserts, lower front fascia and most challenging for me a windshield that will look right on this car. All the parts were designed in Fusion 360 and printed on my Tronxy 3D printer.
Cheers
Steve
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November 1, 2021 at 11:10 am #20068Anonymous
Steering arms, rollbars,pushbars etc. are easy enough to make from piano wire and bits of aluminum.,……….likely a touch more realistic than painting plastic/resin bits.
Cheers
Chris Walker
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November 1, 2021 at 2:58 pm #20069
Hi Chris
That’s one great looking roadster. I’m trying to work on my 3D printing and design skills so I’ve been concentrating on trying to design the parts in Fusion 360 and produce the parts on my Tronxy printer. I’ve learned that wire, metal, epoxy and solder can give me both a quicker and better result for small parts and I do still intend to use them on my models but I got back into slot cars mostly because of nostalgia and on this particular project I was trying hard to preserve some of it’s essential “Eldonness”, the parts being just slightly out of scale and made of plastic help to maintain that feel for me.
I’d love to see the chassis you built for your roadster. I’ve used a printed chassis for this model but I feel that brass and wire chassis or the aluminum ones that Ken makes still have a performance advantage because of their greater tunability and precision.
Cheers
Steve
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November 1, 2021 at 3:33 pm #20072
Great looking work Steve, and from the schematic/plan below the car, I think you could print a 1:1 version too! :>)
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November 1, 2021 at 4:13 pm #20073Anonymous
Hi Steve, the chassis under the Watson Roadster is a fairly straightforward single rail flexi-board design, identical to the chassis below, which is under a Lotus 16.
For low powered motors and skinny tires, it is the execution of the chassis (must be square and flat) rather than the design, that will result in a good handling car. That said, a chassis with the correct amount of torsion flex will outperform a “rigid” chassis all day long.
Cheers
Chris Walker
This chassis design is under the “Roadster”…….it is powered by a BWA FC-130…………this particular chassis is under a Lotus 16,…which explains the “wobbly” wheels.
And this is the Lotus 16…………..
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November 1, 2021 at 6:03 pm #20074
Chris
That chassis is a thing of beauty. I need to figure out how to translate those design and construction principles to a front motor lay out.
Cheers
Steve
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November 4, 2021 at 9:26 am #20135
I second those comments!!!
Also, I still have one of racer68’s 3D printed chassis for anyone who needs a chassis for under their DArt Watson Indy Roadster or any other model with a similar wheelbase…
Thanks again racer68 for taking the time to design that chassis!
Cheers!
The Happy Canadian Scale Modeler!
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November 4, 2021 at 10:31 am #20139
Hi Art, I will take the chassis if it is still available. Do I order it thru the online site? Thanks Dave
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November 5, 2021 at 3:07 pm #20140
Hi DB,
I set that chassis aside for you. I emailed you this morning about arrangements to get it.
Cheers!
The Happy Canadian Scale Modeler!
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November 18, 2021 at 9:36 pm #20503
What size tires are folks using? I am thinking about using 14.3 X 5mm wheels from Pendles, then using a D7 (Front) and D7.5 (Rear) tire. Interest in what others are using?
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November 19, 2021 at 8:43 am #20504
Hi DB,
I’m using D7.5 front and back mounted to 14mm x 7mm BWA/RS Slot wheels. I trued down the fronts a little smaller and cut the same sidewall detail as in the rears so they match. I didn’t do this trying to keep to scale but just the good’ol eyeball test when compared to the body… overall diameters for the rears are 25mm and for the front 23.3. My chassis jig was set up using the blocks you see in the photo for ample chassis/body clearance.
The Happy Canadian Scale Modeler!
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November 19, 2021 at 12:04 pm #20569
Thanks Art, my thinking is similar so thanks for the information. I will check my rim box to see what RSS rims I have. I am pretty sure I have 5mm rims so I will see. I will order some tires soon then.
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