Rattworks I-90

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Len B

Old Member
TRF Supporter
Jan 19, 2009
Reaction score
BC, Canada
Hello everyone,

I am waiting for a Rattworks I-90 "Yardstick" motor to arrive at my door. Can anyone tell me about their experiences with this motor or other Rattworks 29mm motors? Has anyone attempted to light the motor in any other manner than the "slice of AP"? This motor looks like fun. I'm going to have to build a rocket for it as it's not exactly the kind of motor you just throw into any kit you have lying around. I have some ideas about that though. :cool:

Any experience is welcome.


Len Bryan
I fly Ratt's. I own the I80 and K240, both are OUTSTANDING motors. Very well planned out, and less complicated than the Hypertek.

I suggest buying your reloads from www.PrattHobbies.com because he provides the AP ignitor grain. I have never tried any other way, but I think that just using AP works and is easily done.

In the instructions for building the motor, looks can be deceiving. You want the ignitor head to be seperated from the fill hose with some AP, as you want the AP grain to start the burn, then melt the hose. I had the ignitor right next to the fill hose, it lit and popped a hole in the tube right away and it let out all the Nitrous on the pad.

Otherwise, fun motors! I like the simplicity, and $6 for an I or $40 for a K isn't too shabby;)
Hi Dan,

Thanks for the info.

I'm going to light the motors with AP first off. After that I might try some other methods that have been suggested to me. I can't get the reloads shipped accross the border to Canada with AP in them. I have access to one 24mm AT reload that I can use to cut down into igniter pellets. The I90 motor is coming with 9 fuel grains so I need to look at an alternate way to light them at some point.

Is there significant nozzle erosion with the I80? Does a new nozzle come with the 3 pack of reloads? I missed this information in the documentation, but I'll look again.

Thanks again!

Len Bryan
I have flown the I80 a bunch of times. For a kit I built a Hawk Mountain Raptor with the electronics bay. Also, Aeropack makes a 29mm motor retainer that works with the longer Ratt motors. If you can get a pack of 24mm reloads they come 3 to a pack. Each of these 3 motors can be cut into many heater grains. You should be able to get 15 slugs from a pack. I cut them about a 1/4 inch thick. You will get the best performance with a fill take supply pressure of about 750psi. 700psi works well but if it gets down to 600psi you loose a lot of thrust. It can be hard to get a vertical flight! Did that once! Once... ha... The I80 in my Raptor has gone over 6000ft AGL and done as little as 2400ft AGL depending on supply pressure. 750psi works best. ha..

You get a new nozzle with each reload, which is a very nice feature.

The West Coast Hybrid ignition system may work, but I believe their injector has a well bored into it to hold the mixture, I am not sure, but it is something to look into.