Its been a bit quiet on the Site lately so I'll Post a coupla boring pics just to have some "activity"
The shaft tunnel needs to be ~10 mm larger in diameter than the 12/118 engine's so I need to increase the inner diameter of the flametube to compensate and allow enough airflow to the FTs inner wall .
Thankfully the 12/118 flametube was a bit "generous" with its cross sectional area at ~3.5 inducer areas , so even with the larger flow from this engine I can still get my "standard" 3 inducer areas even with the increase in flametubes ID
12/118 engine flametube front wall die opened out from 134mm ID and is now 145mm ID with 263 mm OD
Nice to have the smell of vapourised cutting oil pervading my workshop once again , its been a while
Without access to a press , I just get the oxy onto the 2mm sheet, and with a suitably sized/shaped "hammer" , give it a flogging to roll the edge , a bit one side first then a bit 180 degrees away , then 90 and 180 again so that its held in place and can't wander as I roll over the rest , I clamp a 6mm thick steel ring over the sheet to keep it flat , a press would be much better and a lot easier .
With thinner sheeting I can get away without the oxy , its good enough for a prototype, the flametube is only a tin can with lotsa holes in it, no need to be too pedantic :-)
Post by slittlewing on May 31, 2021 17:50:25 GMT -5
Fair enough, sounds like you have a good technique nailed. There is a lot to be said for coming up with “workarounds” that enable us to make things with the tools we have available!! It’s a must for this hobby.
As you say, 2mm sounds pretty thick though, 1.2 might make your life easier!!
Yeh , 1.2 mm is what I normally use for the side walls , I might even use it for the front and back walls this time as theres no evap tubes that need mounting in it and I'll be using the same fueling arrangement as Andy used in the kart engine , also I want to keep weight down as much as possible .
Workarounds are a way of life for me, not much engineering done around here, its getting harder to build engines .
Found a piece of 1.2mm stainless sheet amongst by "stockpile" of crap , so decided to start making a flametube front wall .
I needed to mount the stainless on my faceplate and cut out the inner disc , then with a large V belt pully holding the sheet flat against the faceplate I split off the ring .
How I envy you guys who have laser cutting available .
Removing the inner 130mm disc isn't too hard , but the 280 mm cut gets a tad awkward as the lathes slowest speed is too high for stainless at that diameter , but slow and steady small cuts gets it done.
Tomorrow I'll markout the ~200 holes that need drilling in it after I roll over the edges