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 Posted 12/31/2014 11:26:00 AM |
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Hmmmm....I too would guess that the seat is cast foam. Probably a semi rigid, sorta flexible foam. The advantage I see is that you have a metal support for the seat built into your frame....that's good. I suppose the question is if it's wide enough to support the weight of someone then sitting on a semi rigid foam seat. Or if the seat will bend on the sides and break or crack, I guess that's the only possible concern I see but maybe I'm over thinking it and your support is fine. It would depend on the foam used to cast, or a good urethane rubber even.
Otherwise, the mold would be pretty straight forward. By the looks of it I'd make an injection 2 piece mold, maybe even a rigid 2 piece mold.
You've sculpted the core into the backside, another great 'thinking ahead' feature to this seat so really once you have the mold I'd try some foam and urethane rubber and see what works best. I'm now thinking a good 60 shore urethane rubber just might do the trick as well.
Either way, killer build and hard not to say I want one...but I can't even begin to imagine the cost or time needed to build yet another one but heck I'm certainly following your progress.
Good luck bud!
David
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| Posted 12/31/2014 7:27:55 PM |
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Thanks for the input David. I have a steel plate bolted to the seat post, about 75mm wide. Hopefully this is enough to support the seat structure.
After reading your post this morning about a solid urethane seat.. something I'd thought about but dismissed as I thought it would be too solid I've come up with another idea. A one piece silicon mold / with fiberglass jacket. Open ended where it meets with the engine cover. Place a piece of wood inside the mold screwed through the silicon to the fiberglass. This can hold the screws to attach it to the steel plate on the bike. Pour in some shore 60 as you suggested and make an outer skin for the seat. Might drill a few holes in the side on the wood that will fill with urethane to help hold the rest of the seat to it. Now here's the part that I've no idea if it'll work..... cut up an EVA mat into small cubes, mix cubes into a shore 25 urethane and fill the mold!! Hopefully this would give it better absorption then straight urethane. Might make some in a cup to test it's absorption qualities.
What you think? And thanks for your input. You sparked some new thoughts..
www.spidey4fun.com
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| Posted 1/1/2015 9:10:21 AM |
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Last Login: 10/18/2023 12:03:11 PM
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The piece of wood inserted in the mold sounds like the way to go...but, in that case you should probably go with a higher shore urethane rubber. A 60 might still be too soft for the wood core and 'may' delaminate from it. Same if you chop up the mats and add them to the urethane, doubt you'll get the results desired and at best you'll have something like what my kids just made...rice crispy squares  .
The wood idea is great, with holes in it for the urethane to encompass it...but use a much higher, firmer urethane. One that wont flex as much because if it does...it will come free of the wood and just wobble around it.
Really liking the sound of this all. Good luck bud.
David
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| Posted 1/2/2015 2:33:26 AM |
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I think I found the process Im looking for.. perhaps foam that's a little more solid.
www.spidey4fun.com
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| Posted 1/4/2015 11:04:19 PM |
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This should stop the front axle from turning inside the support pipe when the brakes are applied. I've allowed for three different steering angles but may drill some more holes to turn it into a slot at the later date. Depending on how it handles.
Starting on the seat.
www.spidey4fun.com
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| Posted 1/5/2015 7:43:19 PM |
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| Spidey, So Ive just finished going through your build, and as everyone else has already said, Amazing! Very very nice work. One thing I was curious about, in your process did you ever consider using an already fabricated front spindle assembly from maybe a small car or something of that nature? I was toying with that as a way to get the hub, rotor, braking and steering all ready to go in one package (in a manner of speaking) and then just need to attach the whole unit to the tubing?
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| Posted 1/6/2015 2:46:22 PM |
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I didn't look into using a small car front end. First day of looking for parts I was at the local wrecking place to do just that and the guy at the wrecking yard suggested a trailer axle. I will have to make some mods still before the engineer will consider it suitable for use. I'll need a bigger pin and I want to change the bearings to tapered. This will mean cutting out some more steel, which at this point in time is a little tricky with the tools I have.
www.spidey4fun.com
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| Posted 1/7/2015 1:05:30 AM |
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Silicon mold worked nicely. Now to make the two part jacket.
www.spidey4fun.com
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| Posted 1/8/2015 6:47:13 AM |
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Little more... brakes are now working correctly in the workshop.. road test next.
Some of the fibreglass backing for the seat mold done. I've ordered some expanding foam. Now I just need to workout how much to actually use!!
I expect to roll test the bike over the next few days. Might get some video. 
www.spidey4fun.com
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| Posted 1/11/2015 1:46:23 AM |
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Thought I'd push the bike around the backyard to see how it'll turn and if everything works OK. Just need to weld on a limiting bolt for the steering to stop the wheel from hitting the support arm. Also altered the camber so the steering circle is a little tighter.
www.spidey4fun.com
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