Hello, hobby casting from Seattle area for a recumbent motorcycle project

Discussion in 'New member introductions' started by Matus, Nov 27, 2022.

  1. Matus

    Matus Copper

    Hello casters!

    I did my first casting quite a few years ago now. I do lost foam casting and make parts for a recumbent motorcycle project I've been working on:


    It's not weight or performance optimized and is just the first phase of multiple stages to test out the geometry and behavior. I plan to build an optimized version with all new components after testing and refining the prototype.

    Those rear wheel mounting points and the rear wheel hub were all cast by me and then machined.

    In troubleshooting some casting failures I came across Kelly's videos and thus this forum.

    Looking forward to learning many great things here and improving my casting skills!
    Tobho Mott, BattyZ and Tops like this.
  2. Tops

    Tops Silver Banner Member

    That looks like one 'bad Moto Guzzi'...or is it? I am filled with chagrin as my 'good' motorcycle sitting in pieces in the garage.
    Welcome to the forum!
  3. Matus

    Matus Copper

    Thanks for the welcome! Just browsing around for a few minutes and I'm shocked at the complexity of things people are casting with lost foam. I definitely have much to learn to move away from my thick bulky disks and blocks.

    It's actually a Honda CX500, I think those are the only transverse v-twins, I think Honda copied the idea from the guzzis from the 60's. I'd love to put a guzzi v-1000 in this thing. I also have a turbo 650 version of that honda motor that puts out 100 HP from a rare cx650 turbo that I plan on upgrading this one too, but I'm going to test on the 500cc 45hp motor first.
    Tops likes this.
  4. Al2O3

    Al2O3 Administrator Staff Member Banner Member

    Have you built and driven other motorized recumbents?

  5. Matus

    Matus Copper

    Nope this is my first one, there aren't many out there and just a few people building them.
  6. Al2O3

    Al2O3 Administrator Staff Member Banner Member

    I used to race motorcycles..........and I'm scared!

  7. Al2O3

    Al2O3 Administrator Staff Member Banner Member

    It's a cool project Matus. Just a word of caution about hobby casting. In general, the material properties of castings will be poor compared to their wrought alloy cousins, especially so in the "as cast" condition and cast in a hobby environment. Many alloys will need post heat treatment to achieve expected strength. Castings can have hidden flaws that can dramatically affect strength. As a hobby caster, the quality and control of your melt, the source of metal, and the design of the part are all important contribruting factors.

    All of this is true even for commercial/pros but they will (destructively) test, and develop process........we usually make one. I've cast a few critically stressed parts for myself and close knowledgeable friends, but in general, I will not. I'm happy to offer you advice on how to cast a particular part, but my advice would be to make your critically stressed parts like triple tree clamps, drive train parts, from wrought stock.

    When I was kid, if something didn't have an engine on it I thought it must have been an oversight and put one on there. If it already had one, I figured it needed a bigger one and immediately corrected the matter. I always ran with scissors. :)

    Now disclaimers aside, looking at your project, for someone who is building but never driven a recumbent motorcycle and considering adding a boosted V-twin, this is probably the least of your worries LoL!

    Welcome to the nuthouse Matus.

    BattyZ likes this.
  8. Matus

    Matus Copper

    Thanks!! Oh yeah, I'm definitely aware of the severe limitations of castings - especially the ones that I do! I have a healthy sense of self preservation and, I think, being very cautious at every step.

    This is the approach I'm taking:

    - I'm massively over-engineering any cast part, I'm guessing a very low tensile strength of about 10,000 psi, which is like 1/4 that of the lowest common cast alloys you can get from a foundry, and putting a wild safety factor on top of that, at least 8 and often higher over max potential loads, and running FEA simulations in SolidWorks for each aluminum part.
    - I'll stress test my sprues / runners to get an idea of the tensile strength each specific actual casting has, machining them to a 1" cross section and then using a strain gauges actually measure their real tensile strength. Hopefully 2 or 3 samples per part, and re-calculate the FOS for each part based on that.
    - I'll also be calculating the density of each part by measuring the volume (since they are machined and simple shapes this is easier and extremely accurate) and the weight to get a rough idea if their are any significant voids in the structure
    - Most of the parts have either a second backup piece or are backed up with a separate steel part that 'limits' the extent of the failure hopefully enough that I can stop safely.
    - Last I'll be replacing each part in the near future with a legitimate machined from billet part as money permits, to reduce the risks of fatigue failures. Costs have dropped dramatically for custom machined parts I've recently found, even with short lead times, so this is becoming more of an option. I may end up doing this with that hub I posted about since it is now much cheaper than even a year ago.
    - I'm definitely not casting my own triple trees or anything like a aluminum twin spar frame!

    I don't think too hard to make a safe part if you don't care about weight :) For instance that wheel hub, it connects the sprocket to the wheel, has a FOS of 8 over the full engine output at max torque with the wheel prevented from slipping and the vehicle unable to even move, as if you bolted it to a concrete block and applied the max engine torque to it! In reality all it needs to do is overcome wheel slip torque. And it's only half the hub, the other side has a similar part and connects to the rear brake rotor. Both of those spin around a massive 2" diameter steel spindle. If both sides of that hub failed, the wheel spindle will still easily handle the weight of the back until I come to a stop. Most of the parts I'm casting though are more simple bearing and axle spacers that get loaded almost entirely in compression.

    I'm similarly progressing the bike design itself in stages, starting with a simple hard tail low powered chain drive to test the general behavior and geometry out, and I'll be adding additional complexity in phases after successful testing of any previous phase. You can learn more about the design and goals at www.matus1976.com or my youtube channel at https://www.youtube.com/matus1976

    My assessment is that once you start trying to optimize for weight and performance you start pushing boundries and riding at the edge of low safety factors, or using materials that suddenly catastrophically fail like carbon fiber as critical structural components, that's when you start really pushing your luck. When I get to that point, I'll be redesigning the entire bike from the ground up integrating everything I've learned and using all new high end components and professional engineers and fabricators to make a production model.

    Hope that makes more sense and makes it sound less crazy, I definitely welcome constructive feedback.

  9. Matus

    Matus Copper

    Circling back here, after some casting failures of some very simple parts, and the much more reasonable costs in one off custom part making that has sprung up recently, I've decided to take the very wise advice offered here and just remake all these cast parts from billet through CNC machining. I wanted to to do anyway eventually, but decided to do it right away. No critical structural parts will be cast, though I do anticipate casting some non structurally critical stuff in the future still!

    I wanted to share the latest update on my project if anyone is interested too:

    - Matus
    Tops likes this.
  10. Matus

    Matus Copper

    Hi all, just wanted to share an update to my recumbent motorcycle project -
    Tops likes this.
  11. Robert

    Robert Silver

    Very impressive work and design! I always have trouble with weld distortion, especially when trying to maintain critical angles and spacing like you show here.
  12. Matus

    Matus Copper

    Thanks! Yeah it's a constant struggle fighting against welding distortion. When I'm lucky I can use it to my advantage, in a previous video I used it to reduce runout in a welded shaft plate. Most of this is still tack welded only though, so they'll be some heavy clamping and fixturing before final welding to hopefully keep the distortion low enough. I built a 8' frame jig for the frame to keep it under control as well (and I want to make more of these so it'll be useful for that too)
  13. Robert

    Robert Silver

    Are those bevel gears OK without lubrication running in a frame like this? I always assumed they should be enclosed and run in gear oil like a rear diff?
  14. Matus

    Matus Copper

    Oh, nope, I wouldn't think so, not for any length of time. Maybe for a few test rides.

    I plan on enclosing the bevel gears and giving the large bevel gear a sort of molded bowl to continuously scavenge lubricant out of, which coats the small bevel gear too, and after splashing about drains back into the bowl to have the cycle repeat. I'm wondering if I can do something like plexiglass with mineral oil to show off everything going on inside there. Still working out the details on all that though.

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