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BJ Craft X-Drive

Old 10-02-2018, 06:30 PM
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shannah
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Default BJ Craft X-Drive

Hey everyone!
The long awaited BJ Craft X-Drive contra unit is here!! I have been waiting for this unit to install in my Eternity. It arrived the other day and I am now back home and can post the first look.

This is is a beautiful drive unit. The machining and workmanship is really outstanding. This is a twin belt drive, direct coupled contradrive unit with no clutch nor planetary gear system. Read that as low maintenance like the Adverrun. I think the Adverrun is the benchmark these days for power and simplicity. The X-Drive looks like it takes things a step further. It came with the custom BJ Force outrunner motor, beautiful pre-cut CF spinner, precise lightweight AL backplate and mounting system for the Eternity.

I did a weight check and it looks to be about equivalent to the first gen Adverrun at 655g. However, this may be even more powerful than that beast. If so, I can’t wait to get it flying.

B.J. said his goal was to match YS power and performance. Based on my Adverrun experience I think this is achievable.

It it is meant for a 22x22 front and rear prop combo. That’s a real load!

so now the first round of pics. Enjoy!!

Old 10-02-2018, 06:33 PM
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Old 10-03-2018, 05:38 AM
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Price and availability?
Old 10-03-2018, 06:09 AM
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Lighter than Akiba’s Belt drive Contra I think
But heavier than a V4 Contra, which I still think is the lightest available.

What is the weight of the BJ X Drive with its spinner (and prop)?

Any method to adjust belt tension or is it not required?
Old 10-03-2018, 06:13 AM
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How is the weight on this unit (655 gram without spinner and without the rear support) compared to Brenner Contra V4 and Adverrun Contra?
How much weight is the spinner and rear support on the BJ Craft X_Drive?

/Bo
Old 10-03-2018, 09:04 AM
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shannah
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The Adverrun unit in the same config as the picture above weighed 644g. This was the original version with the Kontronik 700-52. Front and rear spinner weigh 15g. Front Spinner, Rear Spinner, Spinner Screw and Backplate weigh 30g. I'll assemble the whole thing and weigh it and post a pic.
Old 10-03-2018, 12:28 PM
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Originally Posted by shannah
Hey everyone!
The long awaited BJ Craft X-Drive contra unit is here!! I have been waiting for this unit to install in my Eternity. It arrived the other day and I am now back home and can post the first look.

This is is a beautiful drive unit. The machining and workmanship is really outstanding. This is a twin belt drive, direct coupled contradrive unit with no clutch nor planetary gear system. Read that as low maintenance like the Adverrun. I think the Adverrun is the benchmark these days for power and simplicity. The X-Drive looks like it takes things a step further. It came with the custom BJ Force outrunner motor, beautiful pre-cut CF spinner, precise lightweight AL backplate and mounting system for the Eternity.

I did a weight check and it looks to be about equivalent to the first gen Adverrun at 655g. However, this may be even more powerful than that beast. If so, I can’t wait to get it flying.

B.J. said his goal was to match YS power and performance. Based on my Adverrun experience I think this is achievable.

It it is meant for a 22x22 front and rear prop combo. That’s a real load!

so now the first round of pics. Enjoy!!

Why try to match YS. Just get a YS,,,,
Old 10-03-2018, 01:49 PM
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Akiba belt drive Contra is 705g minus spinner and props

https://rctech.blog.so-net.ne.jp/2017-02-19

Just as a point for comparison ...
Old 10-04-2018, 05:25 AM
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http://www.morris-hobby.jp/cgi-bin/s...5&GoodsID=1081
The v2 is 665
Old 10-04-2018, 10:24 PM
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The main shaft With the 2 big pulley's is the bearings only mounted in the carbon fiber?? I cant see any housing or "fixing" for them, are the glued in? I think he has used a F(flanged) bearing but dont like to put bearings Direct into a carbonfiber plate

Last edited by RuneG; 10-04-2018 at 10:26 PM.
Old 10-07-2018, 08:40 AM
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shannah
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Hi Rune

The main shaft bearing is pressed into the carbon plate. There is a backing ring on the opposite side. The bearing is a flange bearing.

I don’t know if it is glued in. I will check, but it probably is. This method is very similar to the Adverrun drive. I see no reason to think it will be a problem. I have had no problems on the Adverrun so I really expect this to be as good. I’ll upload a couple more pics showing this.

I’m in process of installing it in my Eternity so I hope to have some real flight performance info soon.
Old 10-07-2018, 08:42 AM
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You can see the backing ring.


Pardon the dust. I have been working on the firewall fit. You can see the flanged bearing


Old 10-12-2018, 02:23 AM
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There's a thread on his X drive going back to 2016. No one in the US has one installed and flying yet though? No head to head specs or subjective impressions by anyone between this and Brenner's V4?

When and where can we order it from and specify what BJ plane it's going in and therefore what custom mounts we want with it?
Old 10-13-2018, 08:22 AM
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shannah
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Hi
B.J. Park has been flying and developing this since the 2016 timeframe you referenced. I am not sure how many other fliers have been testing this, but I think he has had several units in test. I think he flew it at the 2017 WC and also at the recent European Championships. From what I understand, the folks that saw it at the EC recently were pretty impressed. I, personally, have not seen it fly so I can’t offer any comparison.

I am installing it in the BJ Craft Eternity, which is what B.J. has been flying. He shipped the drive to me with a firewall and rear mount that fit the Eternity.

I am happy to try this out and offer my observations. My benchmark is the Adverrun, which I am currently flying in my BJ Craft Agenda.

I don’t know his plan for general release. I will send an inquiry to B.J. about his plans.
Old 10-13-2018, 08:44 AM
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ltc
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If I were to venture a guess, Mike at F3AUnlimited would be the most likely USA dealer for another BJCraft pattern product.

Still curious if/how BJ provides for belt tension adjustment on this drive.
Old 10-13-2018, 11:22 AM
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shannah
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As with the Adverrun, there is no tension adjustment. My experience shows it isn’t a problem. This drive is likely the same.
Old 10-13-2018, 12:38 PM
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Thank you. I had assumed it would require belt tensioning like the OS F3A Drive.
Old 10-13-2018, 02:36 PM
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Originally Posted by shannah
As with the Adverrun, there is no tension adjustment. My experience shows it isn’t a problem. This drive is likely the same.
i'm not really familiar with the Adverrun with up close and personal pictures of the install nor have I run across anyone flying with that yet. How does it compare with BJ's with respect to recommended prop sizes and motor size and current draw that it has? Same for Brennar's V4, how does the Adverrun compare weight and prop sizes and current draw, etc?
Old 10-19-2018, 06:31 PM
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The BJCraft X Drive just showed up on the hobbynet japan website for 189,000 yen, which is just about $1680 usd or 1460 euro.

HOBBYNET
Old 10-21-2018, 10:59 PM
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Hi,
Do you know the size of the motor? 40/25?
Do you know how many RPM it will be reached with 22x22 / 22x22 ?
Arnaud
Old 10-22-2018, 05:14 PM
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shannah
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Hi Arnaud

I am checking to see if I can get any motor specs. I measured the outer diameter of the housing and it is 50mm.
Old 10-23-2018, 12:59 AM
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Thanks.
Old 01-13-2019, 03:15 PM
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ltc
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There appears to be quite a bit of new information up on the BJCraft website about this drive

New page

???? NO.1 RC???? ??? :: X-DRIVE TB (TwoBelts)



X-drive TB (Two Belts) Specification:

# Drive Unit (TB / Super Silent Unit)

Two Belts Type (Single Belt: 1ea / Twin Belt: 1ea)

RPM Lock Contra Drive system (Coaxial)

L: 220mm W: 80mm H: 115mm Weight: 660g (CD Unit + Motor + soft mount + Rear supporter)

Spinner : 82mm cabon (25g)

Pinion 17T / Pully 64T

Gear ratio 1 : 3.764

# BJ FORCE MOTOR (CD Special)

L: 50mm D: 50mm W: 335g

Max RPM : 19.822 @ 40.4v (10S Lipo)

MAX: 4500w (10s 130A / 3 second) Continues : 2800W (10S 80A/ 1 minute)

Shaft: L:40mm / D:6mm

Mount: 4mm*30mm + 3mm*25mm

10 pole / 8khz / Timming 0~5 Degre


Inspection before use.

Recommend to use soft type "threadlocker" of Locktite 222.

This unit has been assembled in BJ Craft, but there may be able to exist mistake.
Before your use, please check and follow the order specified below.


1. Tension check for single belt

1 out of 2 motor mount bolts is supposed to be able to adjust tension for the single belt.

The best efficiency of belts is the most loose tension as long as slip does not happen.

When belt tension is unnacessarily strong, motor baring life is shortened.


2. Check of the 2 motor mount bolts.

Check and confirm again motor mount bolt is secured tightly after checking the belt tension .


3. Recheck and confirm all the bolts are fixed tightly.

If the above three check points are OK, the X-Drive can be operated.

Mount

Please make mount to be matched to the plane reffering to the pictures.

If you do not use soft mount, you may not need to use rear supporter.

Installation of propeller and spinner

The carbon spinner for contra drive is included in the unit.
BJ Craft contra spinner is 82mm diameter x 90mm long only.


1. Takeout 4mm hex bolt of rear drive washer,push back drive washer completely with propeller.
Recommend to use threadlocker when reinstall the 4mm hex bolt.

2. Installation of back plate and rear propeller :
Check the positions of spinner 6 bolt holes, propeller slot in spinner, rear propeller position then fix rear propeller bolt.

3. Takeout 4mm hex bolt of front drive washer, push back drive washer completely with front propeller,
then fasten 4mm bolt tightly (do not need to use threadlocker)

4. Installation of rear spinner : Fasten 6 pcs of 2mm bolts with + drivers.

5. Installation of rear centering disc, Install front propeller.then put washer and tighten the bolt.

6. Installation of 3mm bolt of front spinner and silicon tube : As front spinner is fixed by the tension of slicon tube, which must be over 10mm.

7. Fasten the bolt to become 1mm gap between the front spinner and rear one and check the 3mm bolt slightly to be toutched centering disc to front spinner

# 3 pcs of different size of centering disc are included in the kit. Sellect centering disc to fit your case.


ESC

Recommend to continuous on/over 100A (22*22 F/R maximum 130 A)

“BJ Force Motor" 10 poles, Maximum 20,000 RPM.Timming 5 dgr, frequency 8KHZ, Hard brake.

BJ Force Motor can be used for Low level cheap ESC. most cheap ESC can support to 10 poles / 35,000RPM.
If you want to use 80A-90A small ESC, on the ground check ampere (current) and limit the full throttle to fit your small ESC spec.

As BJ Force motor has relatively strong power compare to its size, tempreture of motor and ESC is high ( shall be explained in detail in the part of motor)

The higher KHZ easily finds out pole position so timming is more accurate, motor runs more smoothly.
Though that lowers tempreture of motor more than lower KHZ. but reduces maximum power and hikes tempreture of ESC.

# Attention

Use acceleration speed slow or make throttle delay big not to happen belt slip

# Idle to full throttle 4 seconds is recommended

If you are in difficulty landing your EP plane, that bcause you did not set delay.( when you use ESC brake strongly)

After maiden flight, slowly reduce delay by inividual throttle work. (as individual throttle work style has big difference)

In case of programable acceleration delay (low to full throttle speed) of ESC, set slow
acceleration at recommended 4 second not 1 sec (factory setting). then make a maiden flight.

For Futaba 18MZ, which enables throttle delay programming, program a delay of at least 4 seconds for acceleration (AFR / Speed / IN 10 , OUT 23)
Do not set the transmitter if ESC can be set.
If the transmitter can set the delay, ESC in its normal state. If you set all of both, it shall be too slow.

If you have ESC and radio which are not able to program throttle delay, you must practice the skill to use very slow throttle.

The belt drive is connected with 2 propellers which have large diameter and motor with strong tension,
motor can be reacted by quick acceleration but propeller does not react due to belt. slip may be happened.

Quick throttle work to be used in 3D flight can cause the belt slip and ESC broken (fire) by wrong timming.
In the case of ESC gets fire, BJ Force motor can also be got fired in its coil.

The slower throttle work is the safer, then step by step reduce the delay to be fit to your own throttle work style.

The X-drive stability margin (perfect non slip of belt) of the drive increases weight,
so problem does not happen in the limit of possible F3A flight.

Most case setting of drive fits to users’ style, but in case of X-drive, user needs practice.


Propeller

#ATTENTION

If you are a fixd throttle contol style ( regardless of speed of plane, control the throttle only low, middle, high), or rough control of throttle and not exquisite throttle management.

Recommend to use 22*18 F/R propeller for maiden flight.

In order to avoid Belt slip, Battery and ESC fire

#The followings are for the F3A flyers who control constant flying speed

22*22 F/R

FALCON 22*22 F/R

The recommended propeller (Ideal for all types of airplanes, Maximum current consumption is 107A)

Brenner 22*22 F/R

TOP PERFORMANCE (Highest performance, but with a higher load than the recommended propeller. Maximum current consumption is 115A)

Mejzlik 22*22 F/R.

(Performance is the same as FALCON. But the load is larger than the Brenner. Maximum current consumption is 130A)
If full open throttle, it is not good, but around 85A is good efficiency.

22*20 F/R

Mejzlik 22*20 F/R.

(Best match, speed/sound/pattern tracking)
Brenner 22*20 F/R.

(It has less load and speed than Mejzlik and is a little noisy.)
Sound improves when you modify a propeller tip, better than Mejzlick

Different propeller matches of F/R

Pattern tracking is worse than using the F/R same propeller.(Better than free type contra system)
See the below Description of Lock/Free Type contra system

Sound is better than in case of using the F/R same propeller.(Air easily passes through the front and rear propeller.)

So far, the Contra drive has not shown any good results in vertical up in use of the 22*22 F/R propeller.

So the prop wasn't used.

The biggest issue with the Contra drive is the lack of speed in strong winds.
So BJ wanted a system that could turn the largest propellers(22*22) to its basic specifications, and that was realized.
Specifically, the motor was developed in order to make 22*22 available for the use of all throttle.

Install the propellers so that they overlap at 45 degrees as shown in the picture.

The X-Drive is a lock type contra drive system that always rotates the propeller overlapping in the same position.

If propeller overlap at vertical and horizontal, not at 45 degrees, it's not good because it's noisy when you control the rudder and the elevator.

This creates a special noise by howling when the rudder and the elevator control and start to move the plane overlapping the propeller tip at the same demension

If not use soft mount the noise is greater when the direct hard-mount is used
In case of this must fit propeller at 45 degrees.

Battery

The following data are the case for a good battery for the F3A and differ greatly depending on air density/ individual flying style.

The current battery is not accurate in the C-rate and capacity shown. This is because each manufacturer tend to describe differently for sale.

BJ has been involved in the research and development of LIPO batteries and has used it since 1999,
but current batteries are all lower capacity than that of the 25C batteries (5000mah 10S weight of 1230g) used by BJ in 2005.

Although a bit difference, all the LIPO batteries in the world use the same powder, the most accurate method of measuring battery output is battery weight.

X-Drive to Battery Match.

C-rate and capacity are not significantly different from the results of the description of following,
because C-rate and capacity are ultimately proportional to their weight。

The following data and results are under the condition of 。。。。。。。。

10 Cell battery,wind speed 5m/sec, biplane, 22*22 F/R , P-19 , 170m of distance

1000g, even if you have a top quality battery, you use a full throttle without limitation,
you will find that it is difficult to perform the second half of the maneuver.
(Limit maximum power to 80A to perform the second half of the maneuver.As the indibidual difference is so big, you shall find out it to fit to you)

1100g, Careful use of throttle work most cases enables second-half of the maneuver. However, it is necessary to be careful about the use of the battery.
(you may need to limit the throttle to the capability of the battery)

1200g, A strong windy day needs attention.
Because of its strong power of battery, a throttle delay can be used to prevent possible belt slip.

1300g, Requires little throttle restriction to finish the maneuver. If you use 85A of throttle limit, you can fly longer time
Throttle delay is essential and should inhibit sudden throttle work to prevent belt slip.

1400g, No throttle limitation is required. The throttle delay must be set sufficiently large.

# Caution

If we don't finish the second half of the maneuer and motor is very hot, we suspect overheating of the motor,
but the BJ FORCE MOTOR will operate normally at high temperatures unless the motor stops.

We recommend changing your battery to a larger one or setting the throttle limit.

The concept of design.

This system is a drive unit which was designed on the position of aircraft designer and flier
This drive is the system which focused only for the improvement of perormance and easier flight.

For instance, higher shaft torque in the middle low throttle position increases stability of the plane in the slower speed.

When i asked that increase motor shaft torque, the engineers who design motor said that this case motor does not perform the smooth turning, we take to increase middle low motor shaft torque instead of giving up the smooth turning

At first, I was satified that the drive unit carried out the improved aircraft design perormance but passing the time,I recognized that exclusive motor will improve performance.

finally exclusiv motor has been produced, right now I need to develop propeller for better performance.
Development is going on and on, as the performance is going better and better,I couldn't decide that which is optimist time to launch.

Even though I launched the drive unit now,the system and the performance of that shall be improved continualy, it shall be also developed for present buyers to upgrade the system easily.

Aircraft design / development of drive system to match to each model / start the development of propeller

Balance of all of the above shall show better performance of BJ CRAFT planes.

Every F3A flier wishes his own customized plane that is not the models I have produced for general fliers.
Being the accomplishment of the above, in future custom shop shall be runned for the specialized individual flier.

X-Drive TB component and its limitation.

X-drive has 2 belts and very calm sound. The composition of the system is very simple and trouble free.

This system is "RPM Lock Type Contra Drive System" that always keeps the same RPM of front and rear propellers.

This system include "BJ FORCE MOTOR", recommend Falcon 22*22 F/R propeller, consumes over 130A at full throttle 100% even if it is different from the batteries used.

You must check the current and recommend to limit 85A at full throttle.

ESC can use 80A though recommendation is on/over 100A, at this moment, also recommend to check your ampere to resist your ESC and to limit ampere full throttle.

Common F3A flight is possible with about 85A at full throttle (it can be different depending on the ESC,if you limit at 70% AFR of full throttle, it shall be 80A)

Power of drive was not limited on the general safety level when the drive system was developed (explosion of ESC and battery).This helps to have very good throttle curve.
For your safe use,you must check the current and recommend to limit 85A at full throttle.

There are many contra drives in the market, they were limited power for their safe use, we sell this system without special limitation of power.

If user does not fully understand the limitation in the above,you may face the states which get fire, belt slip or can be difficult to finish last maneuver because of not enough battery.

If you fully understand these limitation and set the drive fit to you and caefully impeove performance step by step, that will show maximum capacity.
Finally these shall be the source of defeating your competitors in the competition.


here is a link the original page, which had far less information
???? NO.1 RC???? ??? :: BJ Drive system
Old 01-13-2019, 04:51 PM
  #24  
shannah
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B.J. is still updating the website with info as he gathers it. I can say that the data he posted pretty much matches my experience so far.

I am running at about 75% power at the top end. I worked into this slowly and made sure my throttle acceleration is not too fast. I am really happy with the power profile on the drive. It has great low end performance and is very smooth and consistent.

The motor does run hot but that is the way it is designed. I do cool it down between flights.

The Falcon 22x22 F/R is really a good combo. Great overall pace. I am not using a hard brake setting. I have my Jeti brake beginning at 20%, brake ending 40%, brake dead time 0.5sec. You do have to be careful with acceleration. If you don’t delay or slow it down it can slip. You just have to set it up and use the power properly.

I did adjust tension a bit, as he noted on his posting. I iriginally thought this drive had no adjustment but you can rotate the motor to add ir decrease tension on the one belt.

Overall, I’m super impressed with the drive so far.
Old 02-09-2019, 05:28 PM
  #25  
shannah
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B.J. Told me to swap the belts so that the twin belt drives the front prop. He also provided an updated set of CF plates which include a bearing to support the front end of the motor shaft. The sum of all these changes are that the motor is supported and the belt tension is increased. I am able to crank up the power on the drive even more. The belts won’t need adjusting in the future because the new tension setting should be sufficient.

So far this has worked really well. I am keeping the power setting conservative and don’t exceed 90-95A. Tons of power. It is also really good at low throttle torque and overall smoothness. It is a great combo with the Eternity.

I am still very impressed with the sound of the drive.

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