A carbon / Kevlar DJ/Street/trial frame
The latest project taking shape.
I just came to think of, that I have something as unusual (for me), as a drawing to show
It at least gives an idea about what I am on about.
Add to this a removable seat tower, like the old Intense DH bikes had it.
Did you fab your own drop out or cut them from a pre fab'd sheet of carbon?
Made of a sheet that I made a while ago.
More to come the following days, as I am at a mates place working on it.
What happened to the DH bike Mr Magura. I want to see the DH bike!
To be honest, I lost interest in it, so I gave it away to a friend of mine.
Originally Posted by Fix the Spade
The bike it was supposed to replace, has not moved an inch since last summer, so it seems a bit pointless to make another bike to collect dust.
Last summer I built up a cheap and simple single speed DJ 24" bike, and since that bike saw the light of day, all the other bikes have seen little to no use.
Hence this change of direction.
The DH bike still needs a rear end, but the main triangle is done. I guess the guy I gave it to, will finish it during the winter.
Here you got a pic of the current state of the project.
Next step is prepping for stratification, and gluing in the last bits and pieces.
Maybe it's time to tell about the aim and specs.
I want to make this bike as versatile for my specific needs as possible.
So, to be able to use it for street trial, the seat tower has to be removable, and the head tube angle must be like 70 degrees.
For DJ there has to be a seat, so the tower goes on, but in the lowest position.
For AM the head tube angle must be 66 degrees, and the seat can be moved up like an adjustable seat post, but the entire seat tower will be a parallelogram, with hydraulic height adjustment, and the seat angle will rise by itself, as the seat is lowered.
The head tube angle will be possible to change within a few seconds.
370mm chain stays (I like that for some reason)
BB 15mm above wheel center
Fork: RockShox Revelation dual air, lowered to 110mm.
Aim to get the frame including hydraulic adjustable seat height, and saddle, down around 2700g.
So far that seems within reach.
Nice!! Keep it coming Magura.
This project is btw. also the first I will be able to get scanned for voids.
A friend of mine has promised to do x-rays and a CT scan of the finished frame.
Now that will at least make for some nice wall art for the workshop
Ok, time for an update:
The frame is pretty much finished by now, but I'm still lacking a bunch of the metal parts.
Work seems to have gotten much in the way lately. Now I'm just dreaming of the days (like half a year ago), where I worked like 8 hours a week.
Anyhow, I just got around to doing the mould for the seat tower, and will get the layup done tomorrow.
It took a bit more calculations than expected, to get the seat height adjustment right, while maintaining a reasonable degree of suspension of the seat tower boom.
I got myself a RS Monarch for that job, which now just need a few modifications, in order to work as height adjustment/suspension.
A mould for a carbon/Kevlar saddle is also in the cards tomorrow, if things works out as planned.
I'll try to get some pics of things tomorrow, before I put it all back on the shelf for the next couple of weeks.
No, YOU don't understand. You're making an ass of yourself for all of eternity.
Subscribed! Would love to see this one finished.
Ok, no update anyway, as yesterday turned into the biggest fail day.
I experimented with a new type of breather, which I considered marginally different from the one I usually use.
Well, not so. It compressed completely, and didn't let the vacuum through.
The result was like 40% fiber content
In other words, the result of this, was something for the bin.
Back to square one, and no more experiments for now. This bike simply has to run before Christmas.
Aww man. That's an f7u12 moment. I'm sorry to hear that.
The way the seat-tube is diagonally cut looks like it could hurt in a bad crash. Mebbe should have laid the TT over it .....
Just random thoughts - don't like my musings get to you.
Bummer on the Breather not bleeding off excess resin. 40:60 resin content is a bit rich, pretty much like a chopper gun built boat, not good.
I'm guessing the breather was a prepreg spec breather.
OK, so now the big question, the Kevlar is obviously hybrid into the lay? Assuming you used 49 based Kevlar and not 29, plus hopefully it was not dyed unless an exterior decorative ply.
You build some cool stuff.
Reps! We don't need no stickin' reps!
Yes 40:60 is a far cry from the approx. 70:30 we usually get.
Originally Posted by PMK
Back to pressure and heat. To be honest I don't know why I all of a sudden found it smart to vacuum bag this, when the rest is made with pressure bladders.
The breather was sold as wet layup type, but it looks different from the usual type, so it may be intended for prepreg. I didn't know there is a difference between the two.
Fact is though, that roll of breather is no longer to be used for its intended purpose.
Yes it's a K49. I have tried playing around with K29, but never managed to make it work with carbon. It seems to be too soft, and I either had to use a very flexible epoxy, ot the epoxy would crack if you looked at it wrong.
By hybrid, do you mean weaved into the other layers, or just made in the same layup?
Originally Posted by Mr.Magura
Technically there is not really a prepreg vs wet layup specific breather. It comes down to the prepreg starting life around a 55:50 resin content so much less is bled off and therefore the breather is not choked. They do offer some breathers that won't "crush" flat to low flow under the higher pressures attained in claves or non vacuum bag setups.
As for hybrid, I was asking in regards to two materials in one ply. Hybrids can also be two materials in the same layup.
As for your previous choice of K29, I can imagine it was not optimum in a structural type application. K49 is a structural type aramid and will layup easily. Why are you using the K49, protection or flexibility of the component?
Send me a PM about what specific brand and weight plus other details about the breather. Maybe I have some laying around and can offer more experience details on using it.
Reps! We don't need no stickin' reps!
So it's a hybrid but it is a layer of K49 on top of the carbon.
Originally Posted by PMK
It is part of something I did some testing on a while back.
With K49 in the layup as the outer layer, and 0.3mm titanium sandwiched on with a 1mm neoprene layer afterwards, it seems to be virtually unbreakable.
I did the tests on a square edge, which is my concern for the downtube in that place.
I have not made any experiments with a 50-50 carbon/K49 layer. Would I get a better result with that for this application?
I tried to find out what type the breather that failed is, but the company I bought it from claims it is the same as I usually get, which it obviously isn't.
Sound like a good time to change supplier.
You are most likely right, that the breather that failed, crushed under the pressure.
I compared it to the breather I usually use. It can carry much more load, and seems to have a more open structure as well.
Thanks for the offer to help though, much appreciated. You obviously have a load of experience in this field.
The good news of today, is that I finally managed to make the titanium rear axle inserts.
If there ever was a nasty piece of work, this would be it.
It took like 3 hours to make them, as I lack power for machining that big diameter titanium. I only had 50mm diameter laying around that was big enough. It ended up with two inserts of 13g each, and a whole lot of Ti chips.