Issue loading fuel slugs in phenolic liner on a 75mm L875DM-P DMS

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JP Shaw

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Trying to assemble my 75mm L875DM-P DMS motor. The fuel slugs start to bind up in the phenolic liner before the first one is half way in. Has anyone had the same issue with this motor? Has anyone lightly sanded the cardboard around the slugs to get them to fit better or use silicone lube?
Thanks,
J. Shaw TRA 08283 L2
 

Cesaroni Technologies

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Trying to assemble my 75mm L875DM-P DMS motor. The fuel slugs start to bind up in the phenolic liner before the first one is half way in. Has anyone had the same issue with this motor? Has anyone lightly sanded the cardboard around the slugs to get them to fit better or use silicone lube?
Thanks,
J. Shaw TRA 08283 L2
Try peeling off the outer layer of paper from the grains.
 

heada

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Those slugs are commonly called grains. You can sand the outside of the grain slightly to ensure they fit into the liner. I thought Aerotech included that in the instructions but I haven't read them lately.
 

JP Shaw

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Thanks. It was easy to do and the fuel slugs slid into the liner with no problem. It was 'fun' seating the o-ring in the groove between the aluminum forward closure and the case. The o-ring would bulge up as I tried to get the last pushed into the groove. But perseverance and two big tongue depressors worked. Now just waiting for the epoxy to cure.
 
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JP Shaw

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Those slugs are commonly called grains. You can sand the outside of the grain slightly to ensure they fit into the liner. I thought Aerotech included that in the instructions but I haven't read them lately.
Yes, you're right. They are called grains. I guess 'slugs' sounds a little crude. But I did peel off the outer layer cardboard the the fuel grains went in smoothly.
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heada

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Word of warning with o-rings. They work when compressed but not when kinked or nicked. Make sure that it has a full, even seat all the way around and that it didn't bunch up (kinked) or that it didn't get cut (nicked). The o-ring is needed to seal the chamber from the hot combustion gases and a kicked or nicked o-ring can cause a motor failure.
 

Rocketclar

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I don't think you need to stress out over the o-ring for the forward closure. Awhile back when I was talking to AT about some M-1350 case issues, I was told that that o-ring was mainly to keep the epoxy from going into the top grain.
 
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