My interpretation of the IFMAR 91 car

[fredswain]

Somewhere around 4 years ago I started working on the 91 IFMAR car. As more pictures became available over the years it became easier to get a more accurate representation of various parts of the car which were impossible to tell from only the old pdf pictures available at the time. I've worked on this off and on since then but am now finally nearing the end. Overall I'm happy with it. It might not be exact to the originals but I'm confident that it's the most accurate representation yet. The only way to be completely accurate is to directly measure one. Making sure everything lines up properly has been extremely tough. Some parts of the originals were clearanced to fit anyways and other parts are just plain tight. Trying to replicate that has been tough. Anyways, here are a couple of pictures. I'm still working on the bellcranks and have a copy of tiny little cleanup tweaks to do in the models. I'm going to print one of these up. Justin is getting the other one as he's been a big part in getting many questions answered.

[jbmeyer13]

This has been an interesting project to say the least. When we started it 4-years ago I thought it would be a few months but it's been a much longer journey with periods of intense focus followed by long bouts of stagnation. I have a new found appreciation for the R&D process for scale R/C models.

This project inspired me to start working with AutoCAD and that alone has been an incredible learning experience. Having drafted the chassis and shock towers (2-D) I have a tremendous amount of respect for Fred's skill in 3-D modeling the parts- his attention to detail and tireless efforts to get it just right simply can not be understated. The front bulkhead and front suspension/steering were massive time sucks that had seemingly countless iterations.

The process of having 30 degree carbon fiber panels fabricated with the right material and then precisely machined via a jig was both time consuming and expensive. To some degree I had taken these aspects of the process for granted early on but learned a lot as the project progressed.

[Mr. ED]

Very cool!
To me this is by far the most inspiring rc10 design from BITD

[XLR8]

Really nice work guys. As someone who has also tried to reproduce accurate designs with only old photos or line drawings to work from, I can fully appreciate the effort that has gone into this. It looks great!
Are you planning to build a runner?
I fully agree with Mr. Ed. I see this car as the ultimate vintage RC10 racer and it's made even more special by the fact that it was never mass produced.

[jbmeyer13]

Are you planning to build a runner?

Without a doubt;-)

[TRX-1-3]

Hey cool. It was fun to watch the other "other" interpretation come to life. There was some drama there for a sec. iirc. The hardcore of the hardcore, the 1%'rs out there, could end up with both interpretations sitting on the shelf next to each other?

What if the measurements were averaged across all dimensions between the two and a third "super tweak" edition was made?

It would be interesting to compare the two.

Good luck on the next phase.

[fredswain]

I've publicly stated that the NIX91 is wrong in many areas but that's not to say I'm critical of it. It was designed only off of pictures from that Detroit pdf and there were many things you just can't see. It was a remarkable achievement under the circumstances. We only know certain things are wrong because it was put side by side with the real thing and because we have additional detail photos now. I'm sure if that info had been available back then, that car would be damned near perfect. I have nothing but praise for what Niki created with so little info.

I can't claim mine is perfect either but I'm confident that it's more accurate. I hope it'll be photographed next to a real one as well and if any differences are evident, I'll change it. I'm starting to work on the 89 car as well. It should be easier and there are actually things on the 91 car dimensionally that carry over.

[jbmeyer13]

Fred and I began this project prior to the NIX91 being released. Once his version was released I even used the NIX parts on various plexiglass mock ups when tweaking wheelbase dimensions.
In the chassis development phase I asked Niki to modify his bellcrank model slightly to use as a placeholder to help facilitate the front end coming together which he kindly did. Nothing but praise for his work and contribution to this community.

[jbmeyer13]

Here are a couple of shots through dev phase

[mikea96]

Are you guys planning on making this available like the nix 91 was?

[fredswain]

Are you guys planning on making this available like the nix 91 was?

While it's easy to load the printed parts to Shapeways, no shock towers or chassis kits will be made. This was strictly our own project. I've learned from chassis in the past that everyone complains about how expensive it is, it's a ton of effort, and in the end is a lot of work to make it happen where there's no money to be made from them. I have no interest in going through that again.

[XLR8]

Notice in this image that the axle centerline is ahead of the diff. Perhaps this will increase rear weight bias and if these cars had a tendency to understeer this might be partly to blame. While doing your research, did you find any options to alter the axle location as is the case with the production RC10?

It would be awesome to own and run a very precise replica such as you have here. Short of that, I would settle for something like an aluminum chassis car if that's the best I could do. Are you concerned about possible breakage with the Shapeways parts?

[fredswain]

Keep in mind that it's only ahead of the centerline of the outdrives because of the rear toe built into the arm mounts. If they were at 0° they'd be inline. The picture isn't quite dead on from the side either but yes the driveshafts do slightly angle forward.

As I only intend mine to be a shelf queen replica, I don't really care about reliability issues from printed parts. Yes, they are more fragile. That's just the current nature of the technology. The goal was to make as authetic of a replica as possible, not to make as authentic of a runner as possible.

Here's a top shot of Masami's car for comparison on the rear axle angle.

[XLR8]

Ah, I see what you mean; the perspective in that image can be tricky.
I reckon one could order a set of parts from Shapeways then set about finding ways to re-make them in stronger materials. For instance, I think that the arms could be routed from sheet stock like those from Dynotech. Of course arms made this way wouldn't include that beautifully complex trellis framework of the originals but at least maybe they wouldn't break either. So long as they accurately capture the hinge point geometry of the originals, the alternate material and simplified design shouldn't detract significantly from relative performance.
I guess I'm at the opposite end of the spectrum; I'm more interested in the experience of drive the car and less interested in keeping a pristine example on the shelf... although the thought of having an awesome car like yours to admire definitely has its appeal.
So, with this one completed, you're moving on to the 89 car next?

[fredswain]

It would certainly be fun to have one to drive but the material properties of printed parts vs nylon or even machined delrin are very different. You could have a car that looks like an original but it most likely will not drive like one. If I were going to build one to drive, I'd modify it a bit to be more tunable. I'd add some camber link location options, would widen the arms to allow modern offset wheels without wide axles and would probably modify the rear bulkhead so the rear tower mounts behind it, putting the rear shocks perpendicular to the arms rather than leaning forward a bit. If that were the case then I'd build the rear camber link locations into the rear tower. At that point it wouldn't be a 91 replica anymore and at that point designing a whole new car that had it's looks inspired by the 91 car is what would be happening. The 91 car had lots of design and geometry flaws to it. If it didn't, they'd have built them and sold them. Instead we only saw certain design elements get integrated slowly over the years.

I've already started the 89 car. It's going to be far easier as many dimensions transfer between the cars even though the looks are different.