I've broken the Optima Mid.
 

I raced the Mid yesterday at Batley Buggy Club in the vintage class. The car did pretty well but unfortunately in practice another driver with a modern 4wd got it all wrong, shot over the track divider and ended up running into me virtually head on. The outcome is a broken front wishbone and a badly bent pin.

What are people doing for replacement front arms? Ideally I would like plastic ones but has anyone tried these:

http://www.pargustore.com/kyosho-opt...-arms-set.html

I've not tried the wishbones, but have used other pargu stuff and it has been good. Will watch this thread with interest as I also have no stock of spare wishbones for my optima - wonder if anyone on here with a 3d printer is able to make them out of abs?
I keep scouring ebay but they never seem to come up!!

Ideally I'd try to stay with plastic: I have no doubts that Pargu's wishbones will be strong enough, I think the concern is with the surrounding parts. I see the Optima Mid has a metal hanger (which will help a lot), but I can see you tear apart the front transmission casing instead.

3D printing may be an alternative: I'm using 3D printed arms on my FWD Buggy, and you're seeing it more and more - a nice example is JQ's 1/10 4WD Buggy, where pretty much everything plastic is 3D printed.

I also came across this thread (link) - These seem like arms that were machined - or cut with a laser/water jet cutter and then had the holes cut in them. The result is a bit of a bulky looking arm, but they are in plastic and the fabrication of them is quite easy and might actually be the cheapest option.

If you're interested in the 3D printing or cutting options, please send me a PM, I may be able to help you out :)

Edit: It may also be worth checking if there are a few more of the Optima Mid arms available - I just found another link showing other machined arms from a different user! (link)

Alcyon is using custom suspension parts as well, he has a topic running on this forum

Yes i make very strong mid arms. I also make strong hingepins out of dowel pins.

I would buy Alcyons rather than Paragu as Paragu doesnt make exact copies. Alcyon makes a good quality product plus you dont want to over strengthen areas where you could snap the chassis, Alcyons items would be perfect for the job.

Are yours made from plastic? Do you have any pictures??

Luckily nothing else got broken in the incident.

His arms are nylon and for a quick fix you can get drill blanks off eBay to use as hinge pins they are a lot stronger over standard pins and a lot cheeper

I've used Shapeways for various Procat parts, including castle to hex wheel adaptors, which take a lot of torque.

https://www.shapeways.com/shops/3DJF

If someone has a spare wishbone and possibly pivot pins they can lend me (I assume they are symmetrical), I could get it modelled up for printing - I use Pro/e for a living.

Wishbones are essentially flat and thin, so print cost shouldn't be astromical for a trial.

Cheers,

Dan.

Have a word with John Price if your looking at 3D printing I'm sure he's got/getting some done for his xx

Yes made out of Delrin.
http://i185.photobucket.com/albums/x...pst36dcvzk.jpg
http://i185.photobucket.com/albums/x...psrhovtm3z.jpg
I have broken my front lazer wishbones before. But I have perfected the design by removing all the stress points. The optima mid ones do not have stress points, and still have not broke after 6 months of abusive use, so its a safe bet. If you seen my videos you would know how abusive the conditions can be on my Mid. Both LWB and SWB.

Hi Dan,

I've got the wishbone that's broken if that's any good as an example?

Attachment 75086

That and pivot pins for accurate measuring wiil be fine.

I'll pm my address - should be simple enough to model.

Cheers,

Dan

As far as i know..for 3d printing you only have 2 choices of materials..abs and pla..both are pretty weak. Thats why i did not invest in a printer just yet.

I was talking to a guy the other day about printing as he's just bought a 3D printer and has just got some nylon to print with, he said he's going to do some test peices and then hopefully some arms.

I've read something yesterday about a guy 3D printing in nylon. It will be interesting to see how strong the arms are. If the material is strong enough you could pretty much make any hard to get part replacement :thumbsup:

Has anyone tried one of these ebay 3D printers? Some of them are under £500 but I can't see them being much good?

strength issues with 3d printing parts are quite often not helped by people not thinking about the design being built with layers. a flat printed arm will always break easily at the hingepin, as the hingepin is running in the same direction as the laminated layers. build your 3d model to be printed vertically so that the layers are running at 90 degrees to the hingepin and strength will be a lot better, downside is you do end up having to clean up more support material from the part and remove the mouldings that helped keep the part in position, but it will be a lot stronger in use for just a little bit more work

Shapeways 'strong and flexible' parts are sintered from a bath of Nylon powder. Items can be built in any orientation, but cost rockets up as soon as you add significant 'height.

I have been very impressed by strength of stuff I have had done, and indeed, there was a chap at Revival 2014 who successfully ran an Astute with a lot of SLS parts in the front.

That's what niki is using in the nix91 on shapeways for the "race arms" the sls material

3d modelling is now complete. I'll upload file to Shapeways tomorrow.

Screenshots to follow also.

cool, have you thought of making the c hubs too. I would suggest an improvement on the c hubs, increasing the height by 3mm so that ZX-5 knuckles can be used, as well as ZX-5 ball studs, that would help a lot, it would be good to have an option to increase the caster angle also from 5 to 8 degrees for very low grip and rough tracks.

Screenshot of model, uploading to Shapeways now.

http://i213.photobucket.com/albums/c...psjbe8xkzl.jpg

Looking good. I don't know how close the final product will look to the original arms, maybe add a little design twist, so it will always be clear this is a repro-item?

I have the OT-93 bumper from Shapeways and although its a perfect copy you can tell the difference from the surface finish, its not smooth like an injection moulded part.
I might have to get a set of these in blue.
Any chance of doing a Mid front gearbox or LA-26 Lazer wishbones?

Is it possible to dye the parts from Shapeways and/or sand the surface smooth?

I Have this one:-

http://www.ebay.co.uk/itm/3512665475...%3AMEBIDX%3AIT

And this filament
http://www.ebay.co.uk/itm/2011315206...%3AMEBIDX%3AIT

Testing is ongoing.... the resolution is not that great so some final surface finishing is required, but its looking promising.
The biggest issue is printing time, to get good resolution prints can take hours.... even for a quite small part

That looks brilliant Dan. Do you have the link for it in shapways?

Not showing on there yet.

Small issue with file, surrounding notch between pivots on inboard edge - should get it sorted tonight.

Link to current file - can't yet be printed.

https://www.shapeways.com/product/E8...shop-inventory

File now live on Shapeways.

If anyone does try items, please forward any feedback - I don't have an Optima (Schumacher man myself), so have no means to test.

https://www.shapeways.com/product/E8...ionId=55960019

if you can send me the STL file I'll try it on my printer this weekend

Hi Dan,

I've ordered a pair and I'll let you know how they perform. Thanks again for making the file :thumbsup:

No problem - do you want broken original back?

Hi Dan,

no it's OK, just chuck it out.

The replacement printed arms arrived today from Shapeways. My first impression is they are very light compared to the original ones. Not sure if this will make them weak but I'll give them a good test in a racing environment and let you all know how they perform. The picture is a close up and they don't look anywhere near as grainy in the flesh.
Attachment 77472

Run some test prints on my Home 3d printer and its seems pretty good. I only used PLA for the tests and the only issue I was found was that the current orientation meant that the hinge joints were very weak. This was due to the strand orientation (Not an issue with the kit shapeways uses)
This was fixed buy rotating the piece on the bed

I make lots of rc parts on Shapeways for the RC10 and soon the JRX2. I only offer them in white polished. All of Shapeways colored parts are actually white inside with only the outside layer being colored. None of the colored parts is polished. The white polished parts have a much nicer finish to them and they can easily be dyed to any color. Printed parts take dye very well and just soak it up like a sponge so scratching them doesn't easily result in white showing through.

nice to see you are on here too fred !

A friend of mine just bought a couple 3d printers and offered to print me a part or two. Would someone mind sending me the file? It will be a while before I can try it on a car as all my r/c is in storage but i will post a pic once it's printed and share any details from my friend about the printing process itself. Thanks!