Race seat unit for a customers hand made bike....

General Composites Discussions Showcase
#1

Made this after I had to take on work started by someone else which was a little bit… well… I will just say I had to use a mould that had never been used but looked worse than some that had been retired then made a thousand eBay parts by some one in a shed at home…

The lower one has only ever had one part made from it…

So I had a new mould made for the customer and ended up taking on the job completely…
So here is the new seat unit I made last week from a material supplied by PRF. It did not have to be cosmetically perfect as it is a race bike. But the results were very good and not far off as good as VTF 261 in places… It may need a little refining with my lay up to improve it more but it is a good material.

So here is the self supporting seat unit and it weighs less than 900grams at the moment…




#2

Looks good. I’m interested to see how you bond them together since it seems like they’re butt joints.

#3

It is not bonded together as such… each half is laid up then strips with one side left longer to overlap when the halves are bolted together then some more strips of pre-preg are over laid along that seam… It is then bagged and cooked.

#4

i have made a similar race tail for a hayabusa drag race bike and it was a nightmare because i did a wet lay/ vacuum bag on it. how many layers of fiber did you put in that seat ?

#5

It changes with more material on structural areas and less on just cosmetic areas… The tail hump is 2 layers with a T shaped reinforcement which has another 2 or 3 layers… The seat has 6 layers with a H section added which adds another 5 or 6 layers and the structural areas which bolt to the bike are up to 10 layers and where inserts are I have added even more… So it really is depending on where I need strength or just to keep shape…

#6

Thats very nice! Is that 11oz carbon fiber for the face?

#7

200gr/sqm or 6oz I think it works out to be… It is all made of the same material. It weighs just under 2lb or 900gr.

#8

Very nice job but know you have to find a way to make nice connect to the middle. Why didn’t make the bagging for both items at once (connected)? This will give better connection and much more easier to sand it.

#9

Each half was laid up first then it was bolted together and joined down the seams to give a good strong joint. It was then bagged up and cooked… The ridge down the centre is not a great joint down the center of the mould but the pattern maker who did this mould is used to wet lay with out a cosmetic surface so he would wax the seam and lay it all up wet with fibre glass. This was his first pre-preg specific mould and now knows he would have to create a tighter joint between the two halves. But it sands back easily and with the pre-preg taped joints being thicker than the area around them they are very very strong.

Thanks for liking my work too… I am happy with my work and I am looking forward to doing more and more pre-preg parts.

#10

Nice one!

Do you have any photos of the inside showing the centre area (joint)? Just wondering how it was all bolted (the bolts must have been parallel with the surface, did you add some flanges to make that possible)?

I wonder how the parts were originally intended to be joined, strange that they didn’t have a joggle etc. made into the moulds?

#11

If you look at the first photo you can see the mould… The flange which is on both parts and gets bolted together is down the centre of the seat unit… You can see the bolt holes and sadly the guy didnt put locators on the flange surfaces so I had to be really careful bolting it together.But as it is not going to be a mass production part it is not too much of a problem…

I will see if I have some photos of how the two halves are joined but to be honest it is really simple with pre-preg as you bolt the halves together and either cut both sides flush with the flange or cut one side flush and leave the other side 10 to 20 longer for an overlap… It depends on how tight the work space is and the shape to be honest for me… This one was cut flush both sides and then 30mm wide strips wer run down the join to create an overlapping join over both halves and I ran about 4 layers over the whole joint with a few more than that down the seat pad area and I also did several layers at 90 degrees in places I wanted to add a little strength too. Working time is not an issue with pre-preg…

#12

This air box to air scoop joining piece was made the same way. Two halves then strips to over lap the butt joint…



#13

Ah, looking back over it I think I just misunderstood your original description. :o Haha. I was thinking that the two CF halves were bolted together on the internal surface, then prepreg covered over the bolts for some reason. :stuck_out_tongue:

So it actually goes like:
[ol]
[li]lay up each half individually in the mould
[/li][li](trim joining edges?) leave the CF layup in the mould and bolt the mould together
[/li][li]apply prepreg on the internal surface, covering the join
[/li][li]two piece seat unit, magically turned monocoque
[/li][/ol]

Well that sure makes sense now that I think about it! Never thought of that before, nice method! Cheers for the airbox pics as well, that helped. So that would actually be a good technique for any complex part that you have internal access to? You could just do a split mould without worrying about joggle joints etc. I am going to remember this one, could come in handy!

#14

Exactly… If you do it right the joint will be stronger than the rest of the part round it… The vac bag should consolidate the join nicely. It is a good way to make complex cosmetic parts in multi part moulds. The seams can be where you have transitions of weave directions so a herring bone V part is easy to get perfect and you only have to lay up each section at a time so a really big part that can take 2 days to lay up can be done in sections and each section can be bagged to debulk it while you lay up the next section…

If you look at the scoop each half of the opening has its weave parallel with the widest direction so when you rotate the part each side of the join has a perfect V pattern and it looks hard to do but as you are doing it in halves it is really simple…

#15

This are scoop was interesting to make… I couldn’t put the second hole in place as I dont know where it has to go so the mould is a 2 piece mould with only one opening at the front through the nose of the scoop and it is too narrow to put your hand down and too long to reach even if you could put your hand down through it… Oh the fun I had… This my first attempt and it turned out OK… One or two dry spots at the furthest point but nothing a coat of resin painted over it will not cure… haha…