33 replies to this topic

[Sparky]

I do not have the space yet for a press and to be fair, ramming is perfectly workable...or should be. And it's quick when you the into the groove.

I am absolutely sure it is poorly consolidated fuel grain due to a "bouncy" ramming table. It is definitely not overly fast BP fuel, I couldn't have been less zealous here ;-) 

[Sparky]

I spotted a bargain in my local old fashioned hardware store today. A Thor #2 rawhide and copper faced hammer.

http://www.amazon.co...e/dp/B0001P0Y00

I think this will be ideal for ramming, it's quite heavy so will only need a gentle strike and I've two types of surface to play with to see if it makes any difference. Beautiful quality too!

[samboradford]

go on then Ken......

 

I'll add another 2 pence worth.

 

What tubes do you actually have Sparky ?

[starseeker]

Nice one Ken,

 

Really simple and informative video , as they say ,pictures speak a thousand words 

[Sparky]

Maybe of some help and with permission

 

Nice video, I think my basic technique is fine.
 

I suspect my problem is subtle but critical and I'm still betting it is my ramming surface / post and the consequently badly consolidated fuel grain.

 

[Sparky]

go on then Ken......

 

I'll add another 2 pence worth.

 

What tubes do you actually have Sparky ?

 

I think my spiral wound ones are old OB stuff but I have some much better ones I think I got from Pyro supplies. Parallel wound.

[Mortartube]

If you are hand ramming them, what are you ramming them on? A bench or a ramming post on a wooden floor. I had CATO's using both of those as benches and wooden floors bounce and reduce the effect of the mallet. Use a stout wooden post on a concrete or brick surface (a tree stump would be ideal.) That may be the difference between success and failure. Nozzleless rockets are easy. I use straight home milled BP with Elder charcoal and about 1% mineral oil. Use the same tooling that you use for 1lb core burners and a good weighty hammer (2lb club hammer works very well, but just use the weight of the hammer, don't add force or you may ruin the tooling). You should be near to ideal and just need to tweak things a bit for your own purposes. I do NOT rice the powder.

Edited by Mortartube, 08 August 2015 - 11:30 AM.

[starseeker]

I ram mine on a concrete step using 8 to ten medium blows with a dead blow mallet ,i put a newspaper on top of the step and a hardwood board onto of that to ram on ,and also i do not rice either .

[Sparky]

If you are hand ramming them, what are you ramming them on? A bench or a ramming post on a wooden floor. I had CATO's using both of those as benches and wooden floors bounce and reduce the effect of the mallet. Use a stout wooden post on a concrete or brick surface (a tree stump would be ideal.) That may be the difference between success and failure. Nozzleless rockets are easy. I use straight home milled BP with Elder charcoal and about 1% mineral oil. Use the same tooling that you use for 1lb core burners and a good weighty hammer (2lb club hammer works very well, but just use the weight of the hammer, don't add force or you may ruin the tooling). You should be near to ideal and just need to tweak things a bit for your own purposes. I do NOT rice the powder.

I'm with you on this. My old ramming table was too bouncy so I have just installed a much more solid post that is driven about a foot into the ground on a steel spike. I also have my doubts about ricing the powder as I am not convinced it aids consolidation. I have a theory that if you rice then you have to be very careful about how much you add in your increments, I suspect that if you use as much as you would normally that the top of the riced layer does not transfer the compression to the lower granules and you end up with a recurring solid and looser layer as you work up through the grain.

I've noticed this effect on gerbs as I seem to get a far more even burn when I do not rice my composition...the downside is a more messy working area lol.

I'm hoping to do some more testing tomorrow. With my new ramming post and much better copper / leather faced hammer I am feeling confident.

 

[starseeker]

I look forward to seeing/ reading about your results (success)

[Sparky]

OK I've rammed a few motors now.

All using BP with ratio 60:30:10 and a quite short milling time. No ricing, minimal mineral oil and using good convolute tubes (not NEPT ones yet but I now have a couple to try). All made using my new ramming post and leather faced hammer and even before testing I can almost feel the difference just in how well the grain consolidated as I made them.

So I'm keeping it simple to start. I've got places to go to improve more but I want to see if these fly first. If they CATO I am going to add more mineral oil, use the nept tubes and wax the tubes before trying again. IF those CATO then I will back off the BP but to be frank at this point I will be starting to wonder what the hell I am doing wrong lol.

 

Edited by Sparky, 20 August 2015 - 11:24 PM.

[Sparky]

Hurrah!!! I tested 2 motors tonight and had a success and a failure. 

 

So of the two I tested here's what I did:

 

Both used the same fuel which was 60:30(willow):10 milled for just an hour or so in a basic small rock tumbler mill. Mixture of lead and ceramic media.

 

Both now rammed on my much more solid post and using my expensive but nice leather / copper faced hammer/mallet.

 

Both used convolute wound tubes but the first was the cheaper you see around and the other was nept.

 

I used a bulk head in both cases and did not even consider a header lol

Both used fine, good quality bentonite clay for nozzle and bulkhead

 

First major difference in construction was the nept tube was waxed and I may have imagined it but I definitely "felt" a difference in the way it rammed. I waxed it using a similar process to Ned on his forum. Literally filling the tube with molten wax via a funnel and then letting it pour out into a pan. I shall be doing a few more tomorrow.

 

I fused both with green visco just into the nozzle with a hook of visco. I don't know how this happened but I inadvertently used a piece of fast visco for the first rocket. I am careful to seal the fast fuse I do have in separate jiffy bags that are carefully labelled so I have no clue how that got in my box of odds and sods. That's not a mistake I want to make again and is just sloppy so I'm annoyed with myself!!! Luckily it was only a rocket motor test and I had given it a lot of length so I was still a few feet away.

 

Results 

 

Rocket 1 - Very fast launch but either the nozzle or the bulkhead blew out. I couldn't find the tube to inspect it but on the video it looks like it blew out the bulkhead. As I've heard comments about being able to ram comp all the way to the end and no bentonite bulkhead is needed with these core burners I'll be interested what people think. Maybe I was just not consolidating the BP well enough towards the top or I simply didn't use enough clay.

 

Rocket 2 - Probably the quickest launch I've ever had. I've never used 60:30:10 and milled too with any success and it went off like....well...a rocket lol. The lift phase was about 0.9 seconds so with a 1 second delay on the header it would be ideal. No idea how much it would have lifted but it certainly went well. 

 

Next I will repeat the exact steps for rocket 2 with a variety of tubes and compare.

 

I'm hoping it wasn't a one off!

 

I've popped a little video on YouTube, I have a small Ion Air Pro which I put quite close the the launch to get good view of the initial ignition and lift. It proved quite a good idea to help me troubleshoot!

[maxman]

Glad you had success sparky! Personally I think 6.3.1 willow and milled would be well to fast for a 1lb cored rocket that is hand rammed. You might have more luck with that pressed hard. 6.3.1 pine and not milled should be well fast enough even for a 4oz. As the rocket gets bigger the fuel should be slower.

Rod

[starseeker]

If it helps ,

 

I mill the Kno3 and sulphur until super fine , i then screen all the ingredients together through a 60 mesh screen about four times and use .

[Sparky]

Glad you had success sparky! Personally I think 6.3.1 willow and milled would be well to fast for a 1lb cored rocket that is hand rammed. You might have more luck with that pressed hard. 6.3.1 pine and not milled should be well fast enough even for a 4oz. As the rocket gets bigger the fuel should be slower.

Rod

I've been told quite vigorously that I could even use 7:2:1 with waxed nept tubes from one source!

I was also skeptical that I could get this ratio  to work as I always used to use about 55% KNO3. There is a medium to fair chance my Charcoal may be mislabelled.As I have been going through all my stock I've discovered I have way too much willow and seem to be missing my basic pine charcoal.

IF I was using the same ratios 60:30:10 but with pine not willow charcoal and in a fairly basic mill for not that long. Do you think that explains why both my tests did not CATO. I am sure one was a badly rammed bulkhead or nozzle.