JAE Mini Sprint up & running

[martin]

Only put around 5 packs through the boat so far so still early days, This is my usual $12 3800kv outrunner & $20 esc. Once boat is ironed out ill fit a 4400kv inrunner on 3s, Like i said in a previous post if your going to use 3s fit a metal rudder bracket & not the wooden one as it wont stand the extra loads in a turn. Martin.

http://www.youtube.com/watch?v=T5JILTLy-U0

http://www.youtube.com/watch?v=nOUlQEGC8lg

[Chenige]

Which $20 ESC is that and what batteries were you using? I guess I should ask what motor you were using.

Sure is fast.

[martin]

The boat has run faster with a x632 & esc PWM at 16khz,In this vid its a x435 so less pitch & PWM turned down to 8khz. Esc i get from www.giantcod.co.uk & is their 60amp cheapo one (theirs lots of these type of esc in diff amps all over Ebay which are the same esc with several diff names.Lipo is Overlander 3s 2200mah 60c-80c (again UK company). Motor is Mystery 2836 3800kv outrunner.

[monojeff]

Looking Good Martin!!!
Can't wait to start building mine!!

[NativePaul]

I knew it would be, but that is a LOT faster than mine it really is rocking. Was that a full run battery full to empty in 45seconds in the second video?
If you were running on a laid out oval course it would massively lower the load on your rudder those tight hairpin turns are huge Gs.

[martin]

Paul im looking at using a Leopard 2850/4430kv on 3s or possibly HET 1w-30 4400kv but thats in the future,Also thinking of shortening the rudder around 6mm for less drag.That night the vid was shot we done 3 runs that were recorded & total run time was for all 3 runs 2 min 25sec in total & i put 1717mah back in a 2200mah pack. The Overlander 60c are fantastic. The 1.2mm wire drive & 3mm stub running in 2 ball bearings i made is working very well with so little friction & is very reliable up to now with no water going in the boat at all up the tube. Martin.

[martin]

Getting some probs with boom tubes not being strong enough with the loads going through them, The original 3/16" hollow ones snapped first time out with just the lightest touch against the bank. Changed them for 5mm solid carbon & also changed the brass tube that went through the tub to bigger carbon tube so i could use the 5mm solid going through them (3/16" is impossible to get in the UK so went to metric). Even with 5mm solid carbon im getting a crack in the carbon where the 3/32" hole is drilled through that bolts the sponson on to the boom tube, This is the one where the fin is so its the turning loads thats cracking it.Im either looking at not bolting through the boom tubes & using collars or going up to 6mm solid carbon,Either way i wont bolt through the carbon again. Martin

[Brushless55]

Looks kiler man!
not sure I would need the higher kv motor, that thing ripps..

[martin]

Things are never to fast,With the outrunners youll limited to how fast you can push because of their generally lower kv however you can gain speeds over some inrunners because of the extra torque of the outrunner taking bigger props but you are increasing temps. Im using Octura x435 detongued & back cut in the vids & have run faster on simular mod x632. Im going to 4400kv inrunners on modded Octura 1630 prop which i believe will be much faster.

[martin]

About a week or so after these vids were shot i was out testing & had a steering problem & at WOT went head on into the concrete bank. So am rebuilding, Quite extensive damage but rebuildable. Even the lipo which was strapped down shot foward into the rear boom tube where it goes through the tub & pushed the tube foward 1/2" splitting the tub side which in turn put a large impression of the tube in the end of the lipo rendering it no good as it was shorting out & getting hotter 20 minuites after unplugging. Still it did hit hard.

[Gary Mullens]

Paul im looking at using a Leopard 2850/4430kv on 3s or possibly HET 1w-30 4400kv but thats in the future,Also thinking of shortening the rudder around 6mm for less drag.That night the vid was shot we done 3 runs that were recorded & total run time was for all 3 runs 2 min 25sec in total & i put 1717mah back in a 2200mah pack. The Overlander 60c are fantastic. The 1.2mm wire drive & 3mm stub running in 2 ball bearings i made is working very well with so little friction & is very reliable up to now with no water going in the boat at all up the tube. Martin.

Can you post up pic's of your drive system with the ball bearings?

Thanks,
-Gary

[martin]

DSCF0451.jpgDSCF0452.jpgDSCF0453.jpgDSCF0454.jpgDSCF0455.jpg

The flex one is .130" with a 4mm stub, the wire drive is 1.2mm ( .048") with 3mm stub. Both o/d of the bearings are the same diam so both types fit in the same tube

[Gary Mullens]

DSCF0451.jpgDSCF0452.jpgDSCF0453.jpgDSCF0454.jpgDSCF0455.jpg

The flex one is .130" with a 4mm stub, the wire drive is 1.2mm ( .048") with 3mm stub. Both o/d of the bearings are the same diam so both types fit in the same tube

Thanks Martin! So the whole assemble slides into the stuffing tube? I take the collet is what holds everything in place? What type of bearings did you use? Learning as I go, so thanks for the feedback. I'm sure someone else will benefit from the info and pic's.

[martin]

Yes it all slides in & when removing to clean & regrease the whole lot comes out to make cleaning & drying the bearings easy,the alloy tube is separate to the brass stuffing tube so the assembly only goes so far & hits a stop inside the tube. The collet holds it in place, ball bearings are 3mm i/d x 7mm o/d or 4mm i/d x 7mm o/d.

[Gary Mullens]

What do you use for a stop in the stuffing tube and what size is the stuffing tube? Also, In the pics you have the bearings 2 in the rear in one set of pics and 2 bearings in the front. Does it matter?
Thanks,
-Gary

[martin]

The aluminium tube at the rear is 2" long this is machined out inside to take the assembly but only machined to a depth of 1.25" so leaves a step inside the tube so the assembly only goes in as far as the step. The rest of the stuffing tube is 3/16" o/d brass tube, this rear alloy tube plugs onto the brass stuffing tube & is bonded to it then the whole lot is bonded into the rear of the ski.

[martin]

Using 3/16" for the main part of the stuffing i can use either the .130" flex with no teflon liner or i use the wire drive with .098 teflon in the tube.

[Gary Mullens]

Thanks, Do you leave a gap at the rear at the drive dog for drive shaft shrinkage on throttle? What do you use for the bonding?
In your setup are the two bearings at the rear or the front?
Ok, So the bearings are bonded inside the piece of alloy and the alloy is then bonded into the 2" piece of stuffing tube which then goes into the main stuffing tube 3/16". How do you get the bonding to release for servicing?

Thanks,
-Gary

[martin]

With the wire drive i leave a very small gap as theirs no wind up (shortening), with the flex i use a larger gap for wind up. I use 1 bearing at the front & 2 at the rear (you need 2 at the rear to take the torque & side loads as 1 at the rear wears to quick. I have also used 2 both ends as well, the bearings are not bonded into the tube only a slide in fit. Its the 2 tubes that are bonded together then bonded into the boat. I use Z-Poxy 30 min epoxy on all off the builds.

[Gary Mullens]

the bearings are not bonded into the tube only a slide in fit. So the bearings don't go into the alloy piece?

[martin]

Where getting a bit lost here, as an example say the 3/16" brass stuffing tube is 9" long it then has the aluminium tube which is 7/16" o/d x 2" long plugged onto the end of the 3/16" brass stuffing tube. The 2" long aluminum tube is the piece you see coming out the back of the hull which the bearing assembly slides into.

[Gary Mullens]

Gotcha. The alloy piece then plugs into the aluminum tube, correct? Now do the bearings go into the alloy piece or are they on the out side of the alloy piece? If they are on the outside of the alloy piece, then the alloy piece acts as a spacer?

[martin]

Yes that is a spacer in between the ball bearings, this whole assembly ie front bearing, spacer & 2 rear bearings simply slide into the tube coming out of the rear of the boat.

[pyroM!KE]

I like seeing this.Im to the point now of glueing in the tube and having second thoughts..But, Im not racing it..Im just tearing up the local pond...Ill be doing pretty much straight runs just messin around...I want to use the stock tube and flex but I will be running 3s 4400..Pretty much Im at a halt because of the stock flex issues...Hmm..

[martin]

I like seeing this.Im to the point now of glueing in the tube and having second thoughts..But, Im not racing it..Im just tearing up the local pond...Ill be doing pretty much straight runs just messin around...I want to use the stock tube and flex but I will be running 3s 4400..Pretty much Im at a halt because of the stock flex issues...Hmm..

I take it that your refering to some of the stock flexes coming unbonded from the stub joint, this didnt happen to me as i never used this flex but had heard of possible issues so cant comment first hand on this.

[longballlumber]

Martin,

I am curious how you can be sure the bearings aren't spinning on the ID of the brass stuffing tube?

Later,
Mike

[martin]

Martin,

I am curious how you can be sure the bearings aren't spinning on the ID of the brass stuffing tube?

Later,
Mike

Mike these bearings are a nice slide fit in the tube, this is a machined tube to suit the bearings, The stub & bearings spin so freely your never going to spin the o/d of the bearing in the tube unless a bearing siezed. Been using this method for years with no probs re bearings turning, you can soon tell if a bearing was spining as the clean grind marks on the outer ring of the bearing will show witness marks to which ive never had. I know a few that use ball bearings on this way with no probs either. Even the Little Joysway Warrior uses this system with no probs as well. Martin.

[Gary Mullens]

Mike these bearings are a nice slide fit in the tube, this is a machined tube to suit the bearings, The stub & bearings spin so freely your never going to spin the o/d of the bearing in the tube unless a bearing siezed. Been using this method for years with no probs re bearings turning, you can soon tell if a bearing was spining as the clean grind marks on the outer ring of the bearing will show witness marks to which ive never had. I know a few that use ball bearings on this way with no probs either. Even the Little Joysway Warrior uses this system with no probs as well. Martin.

Martin,
Would you be willing to make a few and sell them? I would be interested in one.

[martin]

Im afraid i dont have enough time to make my own things at the moment as i have so many things that i need to get done but time restricts.

[NativePaul]

Martin, my rudder is mounted at stock wooden bracket height and I cut my rudder off just below the water pick up and it still handles the oval and the square well in all conditions, so that was a success as far as I am concerned.

Gary, I lost the stock stub and a prop that had a lot of work in it when my flex came unbonded from the stub, so I believe it is a problem, if you are using plastic/carbon props I would save my cash and run the stock shaft as it lasted quite a while before it broke, but if your investing time/money in metal props I would chuck the stock one out and get a quality .130flex with 4mm-1/8" stub from OSE.