Wanted - ASP91FS Crankshaft

[Nick Cripps]

A fast pass down the runway turned into an emergency landing when the crankpin sheared in the ASP91FS in my Little Toni a few weeks ago 😯

 

 

Has anyone got a spare crankshaft they would be willing to part with?

[Jon H]

The pins on those are pressed in so if you can find someone with a lathe they might be able to turn up a new one. 

[Nick Cripps]

Thanks, Jon, I'll look into that.

[Cuban8]

Exactly the same thing happened to my ASP120FS with under an hour's running................shame spares are so rare these days, but hardly a massive job to repair if you can find someone with the gear and expertise. Nice engines, so worth spending a reasonable amount to fix.

[Jon H]

6 hours ago, Nick Cripps said:

Thanks, Jon, I'll look into that.

 

No worries. There are 2 different diameters though so keep the broken part and the bit buried in the crank web. See if you can find some nice tough steel. Mild will be a bit wimpy. 

[Outrunner]

If the pin is made to a round size like 5 or 6mm maybe you could use a dowel pin cut to length? Made of tough stuff but could be dremeld to length.

[Jon H]

47 minutes ago, Outrunner said:

If the pin is made to a round size like 5 or 6mm maybe you could use a dowel pin cut to length? Made of tough stuff but could be dremeld to length.

 

The bearing journal is smaller in dia than the pressed fit into the web. It needs to be turned unfortunately 

[Nick Cripps]

I'd assumed that the pin would be hardened and then ground to diameter for the big end?

[Jon H]

Just now, Nick Cripps said:

I'd assumed that the pin would be hardened and then ground to diameter for the big end?

 

thats how i would do it 

[Nick Cripps]

Hmm, what size are Laser crankpins? 🤔

[Jon H]

Ours are milled as part of the crank so its all one piece and they cannot be removed. 

[Engine Doctor]

Check if the os 91 crank fits . If it does it will give you more options. I have fitted  old OS 52 cranks into the ASP 52 and the 60 fs to get mates out of trouble as they have Identical measurements but far better quality and the engines run far smoother than the original. As for turning  a crankpin on a lathe they are usually made from a hardened roller from a bearing, silver steel or a chrome steel alloy might do the jobYou will probably need to grind it to size if you go the roller route. The step in the ASP etc  crankpin creates a weak spot any many snap on the line or come loose in the crank.

Edited August 31, 2022 by Engine Doctor

[Nick Cripps]

Thanks, ED, more useful info.

 

I replaced the ASP with a new SC91FS bought at Don Valley earlier this year (for a good price!). I have to say it runs very well with a steady idle, good pick-up and plenty of power.

[John Wagg]

Out of interest how would you remove the remaining pin out of the crank?

I have a SC 30 FS with a snapped off pin that I would repair if possible.

 

[Jon H]

11 minutes ago, John Wagg said:

Out of interest how would you remove the remaining pin out of the crank?

I have a SC 30 FS with a snapped off pin that I would repair if possible.

 

 

you can press them out. I did this on an asp 52 crank when i was bored and messing around with stuff. Its here in a box somewhere

[John Wagg]

4 minutes ago, Jon - Laser Engines said:

 

you can press them out. I did this on an asp 52 crank when i was bored and messing around with stuff. Its here in a box somewhere

Thanks Jon.

Would some heat be of any help or just press out cold ?

And the same for pressing a new pin in ?

 

[Jon H]

3 hours ago, John Wagg said:

Thanks Jon.

Would some heat be of any help or just press out cold ?

And the same for pressing a new pin in ?

 

 

Both parts are steel so expand equally when heated. Heating the crankshaft and cooling the pin may help during assembly but not disassembly but as steel will not pick up like aluminium i would not loose too much sleep over it. A very light lube and an accurate press will do the job.