Custom Racer with Aluminium Frame and Sportster Engine

Hurco550 said:
Yep, described yourself perfectly. Good job.

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I think you’ll find I’m not the one criticising the angle of the swingarm drop or the relationship of the pivot to shock mount, but hey why let the facts get in the way of your perception . ‍♂️


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JPMobius concerns are valid. The basic concerns with that frame are excessive swingarm droop and poor design/choice of materials. We all agree that the work is amazing, but the choice of aluminum in that configuration is likely to have fatigue/strength and rigidity issues with a solidly mounted motor.

I'd like to see that bike completed and running, but I share the concerns that others have expressed.
 
As an engineer I agree with JPM and others with their concerns but lets not count our chickens before they hatch. They have a long way to go and are trying to do something different. I personally like an outside opinion and I hope they do too. Is that not the point of posting?
 
Yeah, it does look like the shock will use up most of it's travel just to make the swing arm level under load, the shock mounts need to be moved, I think.
 
The trade off being jack up under braking?

I'm watching with interest, and wish him the best for his project.
 
if you draw a line through the swingarm pivot and lower shock mount, then a line at a right angle to that line from the lower shock mount forward, that line has to, at full shock compression, be level with or above the top shock mount on the frame.

if it is not, the shock leverage will be regressive, and increasingly so as the shock compresses.

i'd say the top/front shock mount needs to be on top of the cases almost.
 
I haven't posted an update for a few weeks, as we had Chinese New Year and I've been on Holidays.

But now it's BACK TO WORK!

After the work on the frame and swingarm, we started to tackle the fuel tank.

To do it a bit different than usual, we decided to make an FRP tank using the lost Foam Method.
(Yes, FRP is not ethanol resistant. It'll get a Phenol Novolac coating on the inside, to make sure it can stand the ethanol.)

It's the first time for us to make Lost Foam parts and that's why we decided to use this process.
Always interesting to try something new…

The very first step is carving a fuel tank dummy out of foam.

First we cut a rough shape....

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Why not CAD the tank and then machine the foam on your mill? It will take a lot of the messing around with saws, files, and sand paper out of the equation.
 
Why not form one out of aluminum? If I can do it, these guys surely can. Not saying mine is either finished or any good, but I was surprised how easy. That's not the word i'm looking for. It isn't as hard as I had expected - once I worked out the CAD (cardboard aided design).

Or it it has to be composite, why not lay it up in carbon fiber?

I have done the foam plug thing before and it is a PIA to be polite and horribly messy and using the wrap method aka Lost foam, it's not to easy to insert fuel tap bungs.
 
This is cool as hell, I like how you guys are trying stuff you have never gotten to try before and really gathering feedback from the members here.
 
teazer said:
it's not to easy to insert fuel tap bungs.
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It is if you cut the form in half, then glass it back together. We use a similar method for casting recuperators on glass kilns.

I've done a bunch of sculpture over the years in foam of varying types. It's a very easy and satisfying material to work with. Not that hard to do and easy to clean up, if you're set up right. All it takes is some hand tools like rasps, Sure-forms, sand paper, and Dremel bits. People shouldn't write off hand forming so easily.
 
Sav0r said:
Why not CAD the tank and then machine the foam on your mill? It will take a lot of the messing around with saws, files, and sand paper out of the equation.
Click to expand...
It makes such a mess in the mill. Gets in your coolant, in the pump. Everyone I know that does foam/composites has a dedicated machine for it.
 
irk miller said:
It is if you cut the form in half, then glass it back together. We use a similar method for casting recuperators on glass kilns.

I've done a bunch of sculpture over the years in foam of varying types. It's a very easy and satisfying material to work with. Not that hard to do and easy to clean up, if you're set up right. All it takes is some hand tools like rasps, Sure-forms, sand paper, and Dremel bits. People shouldn't write off hand forming so easily.
Click to expand...

+1
There is a reason that pretty much every auto design firm starts with clay or foam, then moves to CAD.
 
Sav0r said:
Why not CAD the tank and then machine the foam on your mill? It will take a lot of the messing around with saws, files, and sand paper out of the equation.
Click to expand...

Never really considered about it.

It's actually nice to hand shape the tank, then I can change/adjust while it's on the bike and make sure I get it how i want it.
Also i can direct sit on the bike and make sure it fits my legs nicely.

Also...I assume that the foam would totally mess up the machine. No idea how i should get all the foam out of the machine, after it's cut...
 
teazer said:
Why not form one out of aluminum? If I can do it, these guys surely can. Not saying mine is either finished or any good, but I was surprised how easy. That's not the word i'm looking for. It isn't as hard as I had expected - once I worked out the CAD (cardboard aided design).

Or it it has to be composite, why not lay it up in carbon fiber?

I have done the foam plug thing before and it is a PIA to be polite and horribly messy and using the wrap method aka Lost foam, it's not to easy to insert fuel tap bungs.
Click to expand...

Why not aluminium?...Mainly because I was curious to try the FRP process once.

I might make it in CF later on...But then I'd still make the Lost Foam one in normal glass first and then use that one as plug to make tools for a proper laminated one (which then could be CF)
We make a lot of CF parts using a Vacuum Bagging process.

With the lost Foam process the laminated parts are not too smooth and need a lot of sanding/grinding after the laminating. If you'd use CF you'd destroy the pattern.

While CF would still be stronger/lighter, the difference would be neglible for a fuel tank.
 
Time again for another Update.

Here's the finished, carved foam Template.

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The next step was laminating a short tube, using a stainless tube as plug.

That tube will be inserted into the tank as tunnel, as I'm planning to mount some switches into the tank.

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Then the big job started.

At first I've wrapped the foam in a thin plastic foil and then waxed that foil.
That prevents the Epoxy from soaking into the foam and gives you a smooth surface on the inside.

After the foam is washed out, you can just peel off the foil on the inside.

I've laminated about 6-7 layers of glass mesh, using epoxy reason.
A filler cap flange, mounting brackets and a hose flange have beem laminated in.

These have just been placed between the layers and all these parts have a perforated section which bonds with the FRP.

After everything has dryped up, we ended up with a very rough surface.

A lot of grinding was required to get everything into reasonable shape.

There are still some imperfections which I need to repair, before the part can be fillered.

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DM_Andreas said:
Never really considered about it.

It's actually nice to hand shape the tank, then I can change/adjust while it's on the bike and make sure I get it how i want it.
Also i can direct sit on the bike and make sure it fits my legs nicely.

Also...I assume that the foam would totally mess up the machine. No idea how i should get all the foam out of the machine, after it's cut...
Click to expand...

J-Rod10 said:
It makes such a mess in the mill. Gets in your coolant, in the pump. Everyone I know that does foam/composites has a dedicated machine for it.
Click to expand...

I forget the name of the material, but for various items (wings, diffusers, end plates, etc) we used a machinable material that was baked after machining to form the mold. No coolant was needed, no dust was created, and the molds are perfect and permanent. No foam required. Clean up was more friendly than an Aluminum job.
 
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